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97b8ee8453
ring_buffer_poll_wait() should always put the poll_table to its wait_queue
even there is immediate data available. Otherwise, the following epoll and
read sequence will eventually hang forever:
1. Put some data to make the trace_pipe ring_buffer read ready first
2. epoll_ctl(efd, EPOLL_CTL_ADD, trace_pipe_fd, ee)
3. epoll_wait()
4. read(trace_pipe_fd) till EAGAIN
5. Add some more data to the trace_pipe ring_buffer
6. epoll_wait() -> this epoll_wait() will block forever
~ During the epoll_ctl(efd, EPOLL_CTL_ADD,...) call in step 2,
ring_buffer_poll_wait() returns immediately without adding poll_table,
which has poll_table->_qproc pointing to ep_poll_callback(), to its
wait_queue.
~ During the epoll_wait() call in step 3 and step 6,
ring_buffer_poll_wait() cannot add ep_poll_callback() to its wait_queue
because the poll_table->_qproc is NULL and it is how epoll works.
~ When there is new data available in step 6, ring_buffer does not know
it has to call ep_poll_callback() because it is not in its wait queue.
Hence, block forever.
Other poll implementation seems to call poll_wait() unconditionally as the very
first thing to do. For example, tcp_poll() in tcp.c.
Link: http://lkml.kernel.org/p/20140610060637.GA14045@devbig242.prn2.facebook.com
Cc: stable@vger.kernel.org # 2.6.27
Fixes: 2a2cc8f7c4
"ftrace: allow the event pipe to be polled"
Reviewed-by: Chris Mason <clm@fb.com>
Signed-off-by: Martin Lau <kafai@fb.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
4971 lines
129 KiB
C
4971 lines
129 KiB
C
/*
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* Generic ring buffer
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*
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* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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*/
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#include <linux/ftrace_event.h>
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#include <linux/ring_buffer.h>
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#include <linux/trace_clock.h>
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#include <linux/trace_seq.h>
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#include <linux/spinlock.h>
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#include <linux/irq_work.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/hardirq.h>
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#include <linux/kthread.h> /* for self test */
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#include <linux/kmemcheck.h>
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#include <linux/module.h>
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#include <linux/percpu.h>
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#include <linux/mutex.h>
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#include <linux/delay.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/list.h>
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#include <linux/cpu.h>
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#include <linux/fs.h>
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#include <asm/local.h>
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static void update_pages_handler(struct work_struct *work);
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/*
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* The ring buffer header is special. We must manually up keep it.
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*/
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int ring_buffer_print_entry_header(struct trace_seq *s)
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{
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int ret;
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ret = trace_seq_puts(s, "# compressed entry header\n");
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ret = trace_seq_puts(s, "\ttype_len : 5 bits\n");
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ret = trace_seq_puts(s, "\ttime_delta : 27 bits\n");
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ret = trace_seq_puts(s, "\tarray : 32 bits\n");
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ret = trace_seq_putc(s, '\n');
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ret = trace_seq_printf(s, "\tpadding : type == %d\n",
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RINGBUF_TYPE_PADDING);
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ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
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RINGBUF_TYPE_TIME_EXTEND);
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ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
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RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
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return ret;
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}
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/*
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* The ring buffer is made up of a list of pages. A separate list of pages is
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* allocated for each CPU. A writer may only write to a buffer that is
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* associated with the CPU it is currently executing on. A reader may read
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* from any per cpu buffer.
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*
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* The reader is special. For each per cpu buffer, the reader has its own
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* reader page. When a reader has read the entire reader page, this reader
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* page is swapped with another page in the ring buffer.
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*
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* Now, as long as the writer is off the reader page, the reader can do what
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* ever it wants with that page. The writer will never write to that page
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* again (as long as it is out of the ring buffer).
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*
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* Here's some silly ASCII art.
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*
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* +------+
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* |reader| RING BUFFER
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* |page |
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* +------+ +---+ +---+ +---+
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* | |-->| |-->| |
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* +---+ +---+ +---+
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* ^ |
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* | |
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* +---------------+
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*
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*
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* +------+
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* |reader| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* | |-->| |-->| |
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* +---+ +---+ +---+
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* ^ |
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* | |
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* +---------------+
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*
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*
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* +------+
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* |reader| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* ^ | |-->| |-->| |
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* | +---+ +---+ +---+
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* | |
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* | |
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* +------------------------------+
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*
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*
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* +------+
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* |buffer| RING BUFFER
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* |page |------------------v
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* +------+ +---+ +---+ +---+
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* ^ | | | |-->| |
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* | New +---+ +---+ +---+
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* | Reader------^ |
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* | page |
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* +------------------------------+
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*
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*
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* After we make this swap, the reader can hand this page off to the splice
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* code and be done with it. It can even allocate a new page if it needs to
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* and swap that into the ring buffer.
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*
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* We will be using cmpxchg soon to make all this lockless.
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*
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*/
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/*
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* A fast way to enable or disable all ring buffers is to
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* call tracing_on or tracing_off. Turning off the ring buffers
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* prevents all ring buffers from being recorded to.
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* Turning this switch on, makes it OK to write to the
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* ring buffer, if the ring buffer is enabled itself.
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*
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* There's three layers that must be on in order to write
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* to the ring buffer.
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*
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* 1) This global flag must be set.
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* 2) The ring buffer must be enabled for recording.
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* 3) The per cpu buffer must be enabled for recording.
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*
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* In case of an anomaly, this global flag has a bit set that
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* will permantly disable all ring buffers.
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*/
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/*
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* Global flag to disable all recording to ring buffers
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* This has two bits: ON, DISABLED
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*
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* ON DISABLED
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* ---- ----------
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* 0 0 : ring buffers are off
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* 1 0 : ring buffers are on
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* X 1 : ring buffers are permanently disabled
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*/
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enum {
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RB_BUFFERS_ON_BIT = 0,
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RB_BUFFERS_DISABLED_BIT = 1,
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};
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enum {
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RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
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RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
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};
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static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
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/* Used for individual buffers (after the counter) */
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#define RB_BUFFER_OFF (1 << 20)
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#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
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/**
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* tracing_off_permanent - permanently disable ring buffers
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*
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* This function, once called, will disable all ring buffers
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* permanently.
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*/
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void tracing_off_permanent(void)
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{
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set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
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}
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#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
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#define RB_ALIGNMENT 4U
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#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
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#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
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#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
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# define RB_FORCE_8BYTE_ALIGNMENT 0
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# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
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#else
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# define RB_FORCE_8BYTE_ALIGNMENT 1
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# define RB_ARCH_ALIGNMENT 8U
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#endif
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#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
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/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
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#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
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enum {
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RB_LEN_TIME_EXTEND = 8,
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RB_LEN_TIME_STAMP = 16,
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};
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#define skip_time_extend(event) \
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((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
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static inline int rb_null_event(struct ring_buffer_event *event)
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{
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return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
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}
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static void rb_event_set_padding(struct ring_buffer_event *event)
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{
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/* padding has a NULL time_delta */
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event->type_len = RINGBUF_TYPE_PADDING;
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event->time_delta = 0;
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}
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static unsigned
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rb_event_data_length(struct ring_buffer_event *event)
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{
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unsigned length;
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if (event->type_len)
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length = event->type_len * RB_ALIGNMENT;
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else
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length = event->array[0];
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return length + RB_EVNT_HDR_SIZE;
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}
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/*
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* Return the length of the given event. Will return
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* the length of the time extend if the event is a
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* time extend.
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*/
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static inline unsigned
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rb_event_length(struct ring_buffer_event *event)
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{
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switch (event->type_len) {
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case RINGBUF_TYPE_PADDING:
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if (rb_null_event(event))
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/* undefined */
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return -1;
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return event->array[0] + RB_EVNT_HDR_SIZE;
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case RINGBUF_TYPE_TIME_EXTEND:
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return RB_LEN_TIME_EXTEND;
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case RINGBUF_TYPE_TIME_STAMP:
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return RB_LEN_TIME_STAMP;
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case RINGBUF_TYPE_DATA:
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return rb_event_data_length(event);
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default:
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BUG();
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}
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/* not hit */
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return 0;
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}
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/*
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* Return total length of time extend and data,
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* or just the event length for all other events.
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*/
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static inline unsigned
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rb_event_ts_length(struct ring_buffer_event *event)
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{
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unsigned len = 0;
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if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
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/* time extends include the data event after it */
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len = RB_LEN_TIME_EXTEND;
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event = skip_time_extend(event);
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}
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return len + rb_event_length(event);
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}
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/**
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* ring_buffer_event_length - return the length of the event
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* @event: the event to get the length of
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*
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* Returns the size of the data load of a data event.
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* If the event is something other than a data event, it
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* returns the size of the event itself. With the exception
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* of a TIME EXTEND, where it still returns the size of the
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* data load of the data event after it.
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*/
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unsigned ring_buffer_event_length(struct ring_buffer_event *event)
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{
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unsigned length;
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if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
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event = skip_time_extend(event);
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length = rb_event_length(event);
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if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
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return length;
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length -= RB_EVNT_HDR_SIZE;
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if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
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length -= sizeof(event->array[0]);
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return length;
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}
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EXPORT_SYMBOL_GPL(ring_buffer_event_length);
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/* inline for ring buffer fast paths */
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static void *
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rb_event_data(struct ring_buffer_event *event)
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{
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if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
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event = skip_time_extend(event);
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BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
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/* If length is in len field, then array[0] has the data */
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if (event->type_len)
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return (void *)&event->array[0];
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/* Otherwise length is in array[0] and array[1] has the data */
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return (void *)&event->array[1];
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}
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/**
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* ring_buffer_event_data - return the data of the event
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* @event: the event to get the data from
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*/
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void *ring_buffer_event_data(struct ring_buffer_event *event)
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{
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return rb_event_data(event);
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}
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EXPORT_SYMBOL_GPL(ring_buffer_event_data);
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#define for_each_buffer_cpu(buffer, cpu) \
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for_each_cpu(cpu, buffer->cpumask)
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#define TS_SHIFT 27
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#define TS_MASK ((1ULL << TS_SHIFT) - 1)
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#define TS_DELTA_TEST (~TS_MASK)
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/* Flag when events were overwritten */
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#define RB_MISSED_EVENTS (1 << 31)
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/* Missed count stored at end */
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#define RB_MISSED_STORED (1 << 30)
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struct buffer_data_page {
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u64 time_stamp; /* page time stamp */
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local_t commit; /* write committed index */
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unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
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};
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/*
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* Note, the buffer_page list must be first. The buffer pages
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* are allocated in cache lines, which means that each buffer
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* page will be at the beginning of a cache line, and thus
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* the least significant bits will be zero. We use this to
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* add flags in the list struct pointers, to make the ring buffer
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* lockless.
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*/
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struct buffer_page {
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struct list_head list; /* list of buffer pages */
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local_t write; /* index for next write */
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unsigned read; /* index for next read */
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local_t entries; /* entries on this page */
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unsigned long real_end; /* real end of data */
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struct buffer_data_page *page; /* Actual data page */
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};
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/*
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* The buffer page counters, write and entries, must be reset
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* atomically when crossing page boundaries. To synchronize this
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* update, two counters are inserted into the number. One is
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* the actual counter for the write position or count on the page.
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*
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* The other is a counter of updaters. Before an update happens
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* the update partition of the counter is incremented. This will
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* allow the updater to update the counter atomically.
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*
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* The counter is 20 bits, and the state data is 12.
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*/
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#define RB_WRITE_MASK 0xfffff
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#define RB_WRITE_INTCNT (1 << 20)
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static void rb_init_page(struct buffer_data_page *bpage)
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{
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local_set(&bpage->commit, 0);
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}
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/**
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* ring_buffer_page_len - the size of data on the page.
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* @page: The page to read
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*
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* Returns the amount of data on the page, including buffer page header.
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*/
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size_t ring_buffer_page_len(void *page)
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{
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return local_read(&((struct buffer_data_page *)page)->commit)
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+ BUF_PAGE_HDR_SIZE;
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}
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/*
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* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
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* this issue out.
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*/
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static void free_buffer_page(struct buffer_page *bpage)
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{
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free_page((unsigned long)bpage->page);
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kfree(bpage);
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}
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/*
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* We need to fit the time_stamp delta into 27 bits.
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*/
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static inline int test_time_stamp(u64 delta)
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{
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if (delta & TS_DELTA_TEST)
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return 1;
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return 0;
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}
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#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
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/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
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#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
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int ring_buffer_print_page_header(struct trace_seq *s)
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{
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struct buffer_data_page field;
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int ret;
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ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
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"offset:0;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)sizeof(field.time_stamp),
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(unsigned int)is_signed_type(u64));
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ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), commit),
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(unsigned int)sizeof(field.commit),
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(unsigned int)is_signed_type(long));
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ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), commit),
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1,
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(unsigned int)is_signed_type(long));
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ret = trace_seq_printf(s, "\tfield: char data;\t"
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"offset:%u;\tsize:%u;\tsigned:%u;\n",
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(unsigned int)offsetof(typeof(field), data),
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(unsigned int)BUF_PAGE_SIZE,
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(unsigned int)is_signed_type(char));
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return ret;
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}
|
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|
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struct rb_irq_work {
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struct irq_work work;
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wait_queue_head_t waiters;
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bool waiters_pending;
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};
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|
|
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/*
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* head_page == tail_page && head == tail then buffer is empty.
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*/
|
|
struct ring_buffer_per_cpu {
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int cpu;
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atomic_t record_disabled;
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struct ring_buffer *buffer;
|
|
raw_spinlock_t reader_lock; /* serialize readers */
|
|
arch_spinlock_t lock;
|
|
struct lock_class_key lock_key;
|
|
unsigned int nr_pages;
|
|
struct list_head *pages;
|
|
struct buffer_page *head_page; /* read from head */
|
|
struct buffer_page *tail_page; /* write to tail */
|
|
struct buffer_page *commit_page; /* committed pages */
|
|
struct buffer_page *reader_page;
|
|
unsigned long lost_events;
|
|
unsigned long last_overrun;
|
|
local_t entries_bytes;
|
|
local_t entries;
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local_t overrun;
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|
local_t commit_overrun;
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|
local_t dropped_events;
|
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local_t committing;
|
|
local_t commits;
|
|
unsigned long read;
|
|
unsigned long read_bytes;
|
|
u64 write_stamp;
|
|
u64 read_stamp;
|
|
/* ring buffer pages to update, > 0 to add, < 0 to remove */
|
|
int nr_pages_to_update;
|
|
struct list_head new_pages; /* new pages to add */
|
|
struct work_struct update_pages_work;
|
|
struct completion update_done;
|
|
|
|
struct rb_irq_work irq_work;
|
|
};
|
|
|
|
struct ring_buffer {
|
|
unsigned flags;
|
|
int cpus;
|
|
atomic_t record_disabled;
|
|
atomic_t resize_disabled;
|
|
cpumask_var_t cpumask;
|
|
|
|
struct lock_class_key *reader_lock_key;
|
|
|
|
struct mutex mutex;
|
|
|
|
struct ring_buffer_per_cpu **buffers;
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
struct notifier_block cpu_notify;
|
|
#endif
|
|
u64 (*clock)(void);
|
|
|
|
struct rb_irq_work irq_work;
|
|
};
|
|
|
|
struct ring_buffer_iter {
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long head;
|
|
struct buffer_page *head_page;
|
|
struct buffer_page *cache_reader_page;
|
|
unsigned long cache_read;
|
|
u64 read_stamp;
|
|
};
|
|
|
|
/*
|
|
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
|
|
*
|
|
* Schedules a delayed work to wake up any task that is blocked on the
|
|
* ring buffer waiters queue.
|
|
*/
|
|
static void rb_wake_up_waiters(struct irq_work *work)
|
|
{
|
|
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
|
|
|
|
wake_up_all(&rbwork->waiters);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_wait - wait for input to the ring buffer
|
|
* @buffer: buffer to wait on
|
|
* @cpu: the cpu buffer to wait on
|
|
*
|
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
|
* it will wait for data to be added to a specific cpu buffer.
|
|
*/
|
|
int ring_buffer_wait(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
DEFINE_WAIT(wait);
|
|
struct rb_irq_work *work;
|
|
|
|
/*
|
|
* Depending on what the caller is waiting for, either any
|
|
* data in any cpu buffer, or a specific buffer, put the
|
|
* caller on the appropriate wait queue.
|
|
*/
|
|
if (cpu == RING_BUFFER_ALL_CPUS)
|
|
work = &buffer->irq_work;
|
|
else {
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return -ENODEV;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
work = &cpu_buffer->irq_work;
|
|
}
|
|
|
|
|
|
prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
|
|
|
|
/*
|
|
* The events can happen in critical sections where
|
|
* checking a work queue can cause deadlocks.
|
|
* After adding a task to the queue, this flag is set
|
|
* only to notify events to try to wake up the queue
|
|
* using irq_work.
|
|
*
|
|
* We don't clear it even if the buffer is no longer
|
|
* empty. The flag only causes the next event to run
|
|
* irq_work to do the work queue wake up. The worse
|
|
* that can happen if we race with !trace_empty() is that
|
|
* an event will cause an irq_work to try to wake up
|
|
* an empty queue.
|
|
*
|
|
* There's no reason to protect this flag either, as
|
|
* the work queue and irq_work logic will do the necessary
|
|
* synchronization for the wake ups. The only thing
|
|
* that is necessary is that the wake up happens after
|
|
* a task has been queued. It's OK for spurious wake ups.
|
|
*/
|
|
work->waiters_pending = true;
|
|
|
|
if ((cpu == RING_BUFFER_ALL_CPUS && ring_buffer_empty(buffer)) ||
|
|
(cpu != RING_BUFFER_ALL_CPUS && ring_buffer_empty_cpu(buffer, cpu)))
|
|
schedule();
|
|
|
|
finish_wait(&work->waiters, &wait);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_poll_wait - poll on buffer input
|
|
* @buffer: buffer to wait on
|
|
* @cpu: the cpu buffer to wait on
|
|
* @filp: the file descriptor
|
|
* @poll_table: The poll descriptor
|
|
*
|
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
|
* it will wait for data to be added to a specific cpu buffer.
|
|
*
|
|
* Returns POLLIN | POLLRDNORM if data exists in the buffers,
|
|
* zero otherwise.
|
|
*/
|
|
int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
|
|
struct file *filp, poll_table *poll_table)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct rb_irq_work *work;
|
|
|
|
if (cpu == RING_BUFFER_ALL_CPUS)
|
|
work = &buffer->irq_work;
|
|
else {
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return -EINVAL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
work = &cpu_buffer->irq_work;
|
|
}
|
|
|
|
work->waiters_pending = true;
|
|
poll_wait(filp, &work->waiters, poll_table);
|
|
|
|
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
|
|
(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
|
|
return POLLIN | POLLRDNORM;
|
|
return 0;
|
|
}
|
|
|
|
/* buffer may be either ring_buffer or ring_buffer_per_cpu */
|
|
#define RB_WARN_ON(b, cond) \
|
|
({ \
|
|
int _____ret = unlikely(cond); \
|
|
if (_____ret) { \
|
|
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
|
|
struct ring_buffer_per_cpu *__b = \
|
|
(void *)b; \
|
|
atomic_inc(&__b->buffer->record_disabled); \
|
|
} else \
|
|
atomic_inc(&b->record_disabled); \
|
|
WARN_ON(1); \
|
|
} \
|
|
_____ret; \
|
|
})
|
|
|
|
/* Up this if you want to test the TIME_EXTENTS and normalization */
|
|
#define DEBUG_SHIFT 0
|
|
|
|
static inline u64 rb_time_stamp(struct ring_buffer *buffer)
|
|
{
|
|
/* shift to debug/test normalization and TIME_EXTENTS */
|
|
return buffer->clock() << DEBUG_SHIFT;
|
|
}
|
|
|
|
u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
u64 time;
|
|
|
|
preempt_disable_notrace();
|
|
time = rb_time_stamp(buffer);
|
|
preempt_enable_no_resched_notrace();
|
|
|
|
return time;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
|
|
|
|
void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
|
|
int cpu, u64 *ts)
|
|
{
|
|
/* Just stupid testing the normalize function and deltas */
|
|
*ts >>= DEBUG_SHIFT;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
|
|
|
|
/*
|
|
* Making the ring buffer lockless makes things tricky.
|
|
* Although writes only happen on the CPU that they are on,
|
|
* and they only need to worry about interrupts. Reads can
|
|
* happen on any CPU.
|
|
*
|
|
* The reader page is always off the ring buffer, but when the
|
|
* reader finishes with a page, it needs to swap its page with
|
|
* a new one from the buffer. The reader needs to take from
|
|
* the head (writes go to the tail). But if a writer is in overwrite
|
|
* mode and wraps, it must push the head page forward.
|
|
*
|
|
* Here lies the problem.
|
|
*
|
|
* The reader must be careful to replace only the head page, and
|
|
* not another one. As described at the top of the file in the
|
|
* ASCII art, the reader sets its old page to point to the next
|
|
* page after head. It then sets the page after head to point to
|
|
* the old reader page. But if the writer moves the head page
|
|
* during this operation, the reader could end up with the tail.
|
|
*
|
|
* We use cmpxchg to help prevent this race. We also do something
|
|
* special with the page before head. We set the LSB to 1.
|
|
*
|
|
* When the writer must push the page forward, it will clear the
|
|
* bit that points to the head page, move the head, and then set
|
|
* the bit that points to the new head page.
|
|
*
|
|
* We also don't want an interrupt coming in and moving the head
|
|
* page on another writer. Thus we use the second LSB to catch
|
|
* that too. Thus:
|
|
*
|
|
* head->list->prev->next bit 1 bit 0
|
|
* ------- -------
|
|
* Normal page 0 0
|
|
* Points to head page 0 1
|
|
* New head page 1 0
|
|
*
|
|
* Note we can not trust the prev pointer of the head page, because:
|
|
*
|
|
* +----+ +-----+ +-----+
|
|
* | |------>| T |---X--->| N |
|
|
* | |<------| | | |
|
|
* +----+ +-----+ +-----+
|
|
* ^ ^ |
|
|
* | +-----+ | |
|
|
* +----------| R |----------+ |
|
|
* | |<-----------+
|
|
* +-----+
|
|
*
|
|
* Key: ---X--> HEAD flag set in pointer
|
|
* T Tail page
|
|
* R Reader page
|
|
* N Next page
|
|
*
|
|
* (see __rb_reserve_next() to see where this happens)
|
|
*
|
|
* What the above shows is that the reader just swapped out
|
|
* the reader page with a page in the buffer, but before it
|
|
* could make the new header point back to the new page added
|
|
* it was preempted by a writer. The writer moved forward onto
|
|
* the new page added by the reader and is about to move forward
|
|
* again.
|
|
*
|
|
* You can see, it is legitimate for the previous pointer of
|
|
* the head (or any page) not to point back to itself. But only
|
|
* temporarially.
|
|
*/
|
|
|
|
#define RB_PAGE_NORMAL 0UL
|
|
#define RB_PAGE_HEAD 1UL
|
|
#define RB_PAGE_UPDATE 2UL
|
|
|
|
|
|
#define RB_FLAG_MASK 3UL
|
|
|
|
/* PAGE_MOVED is not part of the mask */
|
|
#define RB_PAGE_MOVED 4UL
|
|
|
|
/*
|
|
* rb_list_head - remove any bit
|
|
*/
|
|
static struct list_head *rb_list_head(struct list_head *list)
|
|
{
|
|
unsigned long val = (unsigned long)list;
|
|
|
|
return (struct list_head *)(val & ~RB_FLAG_MASK);
|
|
}
|
|
|
|
/*
|
|
* rb_is_head_page - test if the given page is the head page
|
|
*
|
|
* Because the reader may move the head_page pointer, we can
|
|
* not trust what the head page is (it may be pointing to
|
|
* the reader page). But if the next page is a header page,
|
|
* its flags will be non zero.
|
|
*/
|
|
static inline int
|
|
rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *page, struct list_head *list)
|
|
{
|
|
unsigned long val;
|
|
|
|
val = (unsigned long)list->next;
|
|
|
|
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
|
|
return RB_PAGE_MOVED;
|
|
|
|
return val & RB_FLAG_MASK;
|
|
}
|
|
|
|
/*
|
|
* rb_is_reader_page
|
|
*
|
|
* The unique thing about the reader page, is that, if the
|
|
* writer is ever on it, the previous pointer never points
|
|
* back to the reader page.
|
|
*/
|
|
static int rb_is_reader_page(struct buffer_page *page)
|
|
{
|
|
struct list_head *list = page->list.prev;
|
|
|
|
return rb_list_head(list->next) != &page->list;
|
|
}
|
|
|
|
/*
|
|
* rb_set_list_to_head - set a list_head to be pointing to head.
|
|
*/
|
|
static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct list_head *list)
|
|
{
|
|
unsigned long *ptr;
|
|
|
|
ptr = (unsigned long *)&list->next;
|
|
*ptr |= RB_PAGE_HEAD;
|
|
*ptr &= ~RB_PAGE_UPDATE;
|
|
}
|
|
|
|
/*
|
|
* rb_head_page_activate - sets up head page
|
|
*/
|
|
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *head;
|
|
|
|
head = cpu_buffer->head_page;
|
|
if (!head)
|
|
return;
|
|
|
|
/*
|
|
* Set the previous list pointer to have the HEAD flag.
|
|
*/
|
|
rb_set_list_to_head(cpu_buffer, head->list.prev);
|
|
}
|
|
|
|
static void rb_list_head_clear(struct list_head *list)
|
|
{
|
|
unsigned long *ptr = (unsigned long *)&list->next;
|
|
|
|
*ptr &= ~RB_FLAG_MASK;
|
|
}
|
|
|
|
/*
|
|
* rb_head_page_dactivate - clears head page ptr (for free list)
|
|
*/
|
|
static void
|
|
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *hd;
|
|
|
|
/* Go through the whole list and clear any pointers found. */
|
|
rb_list_head_clear(cpu_buffer->pages);
|
|
|
|
list_for_each(hd, cpu_buffer->pages)
|
|
rb_list_head_clear(hd);
|
|
}
|
|
|
|
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag, int new_flag)
|
|
{
|
|
struct list_head *list;
|
|
unsigned long val = (unsigned long)&head->list;
|
|
unsigned long ret;
|
|
|
|
list = &prev->list;
|
|
|
|
val &= ~RB_FLAG_MASK;
|
|
|
|
ret = cmpxchg((unsigned long *)&list->next,
|
|
val | old_flag, val | new_flag);
|
|
|
|
/* check if the reader took the page */
|
|
if ((ret & ~RB_FLAG_MASK) != val)
|
|
return RB_PAGE_MOVED;
|
|
|
|
return ret & RB_FLAG_MASK;
|
|
}
|
|
|
|
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_UPDATE);
|
|
}
|
|
|
|
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_HEAD);
|
|
}
|
|
|
|
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_NORMAL);
|
|
}
|
|
|
|
static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page **bpage)
|
|
{
|
|
struct list_head *p = rb_list_head((*bpage)->list.next);
|
|
|
|
*bpage = list_entry(p, struct buffer_page, list);
|
|
}
|
|
|
|
static struct buffer_page *
|
|
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *head;
|
|
struct buffer_page *page;
|
|
struct list_head *list;
|
|
int i;
|
|
|
|
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
|
|
return NULL;
|
|
|
|
/* sanity check */
|
|
list = cpu_buffer->pages;
|
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
|
|
return NULL;
|
|
|
|
page = head = cpu_buffer->head_page;
|
|
/*
|
|
* It is possible that the writer moves the header behind
|
|
* where we started, and we miss in one loop.
|
|
* A second loop should grab the header, but we'll do
|
|
* three loops just because I'm paranoid.
|
|
*/
|
|
for (i = 0; i < 3; i++) {
|
|
do {
|
|
if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
|
|
cpu_buffer->head_page = page;
|
|
return page;
|
|
}
|
|
rb_inc_page(cpu_buffer, &page);
|
|
} while (page != head);
|
|
}
|
|
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static int rb_head_page_replace(struct buffer_page *old,
|
|
struct buffer_page *new)
|
|
{
|
|
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
|
|
unsigned long val;
|
|
unsigned long ret;
|
|
|
|
val = *ptr & ~RB_FLAG_MASK;
|
|
val |= RB_PAGE_HEAD;
|
|
|
|
ret = cmpxchg(ptr, val, (unsigned long)&new->list);
|
|
|
|
return ret == val;
|
|
}
|
|
|
|
/*
|
|
* rb_tail_page_update - move the tail page forward
|
|
*
|
|
* Returns 1 if moved tail page, 0 if someone else did.
|
|
*/
|
|
static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *tail_page,
|
|
struct buffer_page *next_page)
|
|
{
|
|
struct buffer_page *old_tail;
|
|
unsigned long old_entries;
|
|
unsigned long old_write;
|
|
int ret = 0;
|
|
|
|
/*
|
|
* The tail page now needs to be moved forward.
|
|
*
|
|
* We need to reset the tail page, but without messing
|
|
* with possible erasing of data brought in by interrupts
|
|
* that have moved the tail page and are currently on it.
|
|
*
|
|
* We add a counter to the write field to denote this.
|
|
*/
|
|
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
|
|
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
|
|
|
|
/*
|
|
* Just make sure we have seen our old_write and synchronize
|
|
* with any interrupts that come in.
|
|
*/
|
|
barrier();
|
|
|
|
/*
|
|
* If the tail page is still the same as what we think
|
|
* it is, then it is up to us to update the tail
|
|
* pointer.
|
|
*/
|
|
if (tail_page == cpu_buffer->tail_page) {
|
|
/* Zero the write counter */
|
|
unsigned long val = old_write & ~RB_WRITE_MASK;
|
|
unsigned long eval = old_entries & ~RB_WRITE_MASK;
|
|
|
|
/*
|
|
* This will only succeed if an interrupt did
|
|
* not come in and change it. In which case, we
|
|
* do not want to modify it.
|
|
*
|
|
* We add (void) to let the compiler know that we do not care
|
|
* about the return value of these functions. We use the
|
|
* cmpxchg to only update if an interrupt did not already
|
|
* do it for us. If the cmpxchg fails, we don't care.
|
|
*/
|
|
(void)local_cmpxchg(&next_page->write, old_write, val);
|
|
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
|
|
|
|
/*
|
|
* No need to worry about races with clearing out the commit.
|
|
* it only can increment when a commit takes place. But that
|
|
* only happens in the outer most nested commit.
|
|
*/
|
|
local_set(&next_page->page->commit, 0);
|
|
|
|
old_tail = cmpxchg(&cpu_buffer->tail_page,
|
|
tail_page, next_page);
|
|
|
|
if (old_tail == tail_page)
|
|
ret = 1;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *bpage)
|
|
{
|
|
unsigned long val = (unsigned long)bpage;
|
|
|
|
if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* rb_check_list - make sure a pointer to a list has the last bits zero
|
|
*/
|
|
static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct list_head *list)
|
|
{
|
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
|
|
return 1;
|
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* rb_check_pages - integrity check of buffer pages
|
|
* @cpu_buffer: CPU buffer with pages to test
|
|
*
|
|
* As a safety measure we check to make sure the data pages have not
|
|
* been corrupted.
|
|
*/
|
|
static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *head = cpu_buffer->pages;
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
/* Reset the head page if it exists */
|
|
if (cpu_buffer->head_page)
|
|
rb_set_head_page(cpu_buffer);
|
|
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
|
|
return -1;
|
|
if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
|
|
return -1;
|
|
|
|
if (rb_check_list(cpu_buffer, head))
|
|
return -1;
|
|
|
|
list_for_each_entry_safe(bpage, tmp, head, list) {
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
bpage->list.next->prev != &bpage->list))
|
|
return -1;
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
bpage->list.prev->next != &bpage->list))
|
|
return -1;
|
|
if (rb_check_list(cpu_buffer, &bpage->list))
|
|
return -1;
|
|
}
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
|
|
{
|
|
int i;
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page;
|
|
/*
|
|
* __GFP_NORETRY flag makes sure that the allocation fails
|
|
* gracefully without invoking oom-killer and the system is
|
|
* not destabilized.
|
|
*/
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
|
GFP_KERNEL | __GFP_NORETRY,
|
|
cpu_to_node(cpu));
|
|
if (!bpage)
|
|
goto free_pages;
|
|
|
|
list_add(&bpage->list, pages);
|
|
|
|
page = alloc_pages_node(cpu_to_node(cpu),
|
|
GFP_KERNEL | __GFP_NORETRY, 0);
|
|
if (!page)
|
|
goto free_pages;
|
|
bpage->page = page_address(page);
|
|
rb_init_page(bpage->page);
|
|
}
|
|
|
|
return 0;
|
|
|
|
free_pages:
|
|
list_for_each_entry_safe(bpage, tmp, pages, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned nr_pages)
|
|
{
|
|
LIST_HEAD(pages);
|
|
|
|
WARN_ON(!nr_pages);
|
|
|
|
if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
|
|
return -ENOMEM;
|
|
|
|
/*
|
|
* The ring buffer page list is a circular list that does not
|
|
* start and end with a list head. All page list items point to
|
|
* other pages.
|
|
*/
|
|
cpu_buffer->pages = pages.next;
|
|
list_del(&pages);
|
|
|
|
cpu_buffer->nr_pages = nr_pages;
|
|
|
|
rb_check_pages(cpu_buffer);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct ring_buffer_per_cpu *
|
|
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *bpage;
|
|
struct page *page;
|
|
int ret;
|
|
|
|
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
|
|
GFP_KERNEL, cpu_to_node(cpu));
|
|
if (!cpu_buffer)
|
|
return NULL;
|
|
|
|
cpu_buffer->cpu = cpu;
|
|
cpu_buffer->buffer = buffer;
|
|
raw_spin_lock_init(&cpu_buffer->reader_lock);
|
|
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
|
|
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
|
|
INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
|
|
init_completion(&cpu_buffer->update_done);
|
|
init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
|
|
init_waitqueue_head(&cpu_buffer->irq_work.waiters);
|
|
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
|
GFP_KERNEL, cpu_to_node(cpu));
|
|
if (!bpage)
|
|
goto fail_free_buffer;
|
|
|
|
rb_check_bpage(cpu_buffer, bpage);
|
|
|
|
cpu_buffer->reader_page = bpage;
|
|
page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
|
|
if (!page)
|
|
goto fail_free_reader;
|
|
bpage->page = page_address(page);
|
|
rb_init_page(bpage->page);
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
|
|
ret = rb_allocate_pages(cpu_buffer, nr_pages);
|
|
if (ret < 0)
|
|
goto fail_free_reader;
|
|
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
|
|
return cpu_buffer;
|
|
|
|
fail_free_reader:
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
|
|
fail_free_buffer:
|
|
kfree(cpu_buffer);
|
|
return NULL;
|
|
}
|
|
|
|
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *head = cpu_buffer->pages;
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
if (head) {
|
|
list_for_each_entry_safe(bpage, tmp, head, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
bpage = list_entry(head, struct buffer_page, list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
|
|
kfree(cpu_buffer);
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static int rb_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu);
|
|
#endif
|
|
|
|
/**
|
|
* __ring_buffer_alloc - allocate a new ring_buffer
|
|
* @size: the size in bytes per cpu that is needed.
|
|
* @flags: attributes to set for the ring buffer.
|
|
*
|
|
* Currently the only flag that is available is the RB_FL_OVERWRITE
|
|
* flag. This flag means that the buffer will overwrite old data
|
|
* when the buffer wraps. If this flag is not set, the buffer will
|
|
* drop data when the tail hits the head.
|
|
*/
|
|
struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
|
|
struct lock_class_key *key)
|
|
{
|
|
struct ring_buffer *buffer;
|
|
int bsize;
|
|
int cpu, nr_pages;
|
|
|
|
/* keep it in its own cache line */
|
|
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
|
|
GFP_KERNEL);
|
|
if (!buffer)
|
|
return NULL;
|
|
|
|
if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
|
|
goto fail_free_buffer;
|
|
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
buffer->flags = flags;
|
|
buffer->clock = trace_clock_local;
|
|
buffer->reader_lock_key = key;
|
|
|
|
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
|
|
init_waitqueue_head(&buffer->irq_work.waiters);
|
|
|
|
/* need at least two pages */
|
|
if (nr_pages < 2)
|
|
nr_pages = 2;
|
|
|
|
/*
|
|
* In case of non-hotplug cpu, if the ring-buffer is allocated
|
|
* in early initcall, it will not be notified of secondary cpus.
|
|
* In that off case, we need to allocate for all possible cpus.
|
|
*/
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
cpu_notifier_register_begin();
|
|
cpumask_copy(buffer->cpumask, cpu_online_mask);
|
|
#else
|
|
cpumask_copy(buffer->cpumask, cpu_possible_mask);
|
|
#endif
|
|
buffer->cpus = nr_cpu_ids;
|
|
|
|
bsize = sizeof(void *) * nr_cpu_ids;
|
|
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
|
|
GFP_KERNEL);
|
|
if (!buffer->buffers)
|
|
goto fail_free_cpumask;
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
buffer->buffers[cpu] =
|
|
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
|
if (!buffer->buffers[cpu])
|
|
goto fail_free_buffers;
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
buffer->cpu_notify.notifier_call = rb_cpu_notify;
|
|
buffer->cpu_notify.priority = 0;
|
|
__register_cpu_notifier(&buffer->cpu_notify);
|
|
cpu_notifier_register_done();
|
|
#endif
|
|
|
|
mutex_init(&buffer->mutex);
|
|
|
|
return buffer;
|
|
|
|
fail_free_buffers:
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
if (buffer->buffers[cpu])
|
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
|
}
|
|
kfree(buffer->buffers);
|
|
|
|
fail_free_cpumask:
|
|
free_cpumask_var(buffer->cpumask);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
cpu_notifier_register_done();
|
|
#endif
|
|
|
|
fail_free_buffer:
|
|
kfree(buffer);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
|
|
|
|
/**
|
|
* ring_buffer_free - free a ring buffer.
|
|
* @buffer: the buffer to free.
|
|
*/
|
|
void
|
|
ring_buffer_free(struct ring_buffer *buffer)
|
|
{
|
|
int cpu;
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
cpu_notifier_register_begin();
|
|
__unregister_cpu_notifier(&buffer->cpu_notify);
|
|
#endif
|
|
|
|
for_each_buffer_cpu(buffer, cpu)
|
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
cpu_notifier_register_done();
|
|
#endif
|
|
|
|
kfree(buffer->buffers);
|
|
free_cpumask_var(buffer->cpumask);
|
|
|
|
kfree(buffer);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_free);
|
|
|
|
void ring_buffer_set_clock(struct ring_buffer *buffer,
|
|
u64 (*clock)(void))
|
|
{
|
|
buffer->clock = clock;
|
|
}
|
|
|
|
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
|
|
|
|
static inline unsigned long rb_page_entries(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->entries) & RB_WRITE_MASK;
|
|
}
|
|
|
|
static inline unsigned long rb_page_write(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->write) & RB_WRITE_MASK;
|
|
}
|
|
|
|
static int
|
|
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
|
|
{
|
|
struct list_head *tail_page, *to_remove, *next_page;
|
|
struct buffer_page *to_remove_page, *tmp_iter_page;
|
|
struct buffer_page *last_page, *first_page;
|
|
unsigned int nr_removed;
|
|
unsigned long head_bit;
|
|
int page_entries;
|
|
|
|
head_bit = 0;
|
|
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
/*
|
|
* We don't race with the readers since we have acquired the reader
|
|
* lock. We also don't race with writers after disabling recording.
|
|
* This makes it easy to figure out the first and the last page to be
|
|
* removed from the list. We unlink all the pages in between including
|
|
* the first and last pages. This is done in a busy loop so that we
|
|
* lose the least number of traces.
|
|
* The pages are freed after we restart recording and unlock readers.
|
|
*/
|
|
tail_page = &cpu_buffer->tail_page->list;
|
|
|
|
/*
|
|
* tail page might be on reader page, we remove the next page
|
|
* from the ring buffer
|
|
*/
|
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
|
tail_page = rb_list_head(tail_page->next);
|
|
to_remove = tail_page;
|
|
|
|
/* start of pages to remove */
|
|
first_page = list_entry(rb_list_head(to_remove->next),
|
|
struct buffer_page, list);
|
|
|
|
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
|
|
to_remove = rb_list_head(to_remove)->next;
|
|
head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
|
|
}
|
|
|
|
next_page = rb_list_head(to_remove)->next;
|
|
|
|
/*
|
|
* Now we remove all pages between tail_page and next_page.
|
|
* Make sure that we have head_bit value preserved for the
|
|
* next page
|
|
*/
|
|
tail_page->next = (struct list_head *)((unsigned long)next_page |
|
|
head_bit);
|
|
next_page = rb_list_head(next_page);
|
|
next_page->prev = tail_page;
|
|
|
|
/* make sure pages points to a valid page in the ring buffer */
|
|
cpu_buffer->pages = next_page;
|
|
|
|
/* update head page */
|
|
if (head_bit)
|
|
cpu_buffer->head_page = list_entry(next_page,
|
|
struct buffer_page, list);
|
|
|
|
/*
|
|
* change read pointer to make sure any read iterators reset
|
|
* themselves
|
|
*/
|
|
cpu_buffer->read = 0;
|
|
|
|
/* pages are removed, resume tracing and then free the pages */
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
|
|
|
|
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
|
|
|
|
/* last buffer page to remove */
|
|
last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
|
|
list);
|
|
tmp_iter_page = first_page;
|
|
|
|
do {
|
|
to_remove_page = tmp_iter_page;
|
|
rb_inc_page(cpu_buffer, &tmp_iter_page);
|
|
|
|
/* update the counters */
|
|
page_entries = rb_page_entries(to_remove_page);
|
|
if (page_entries) {
|
|
/*
|
|
* If something was added to this page, it was full
|
|
* since it is not the tail page. So we deduct the
|
|
* bytes consumed in ring buffer from here.
|
|
* Increment overrun to account for the lost events.
|
|
*/
|
|
local_add(page_entries, &cpu_buffer->overrun);
|
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
|
|
}
|
|
|
|
/*
|
|
* We have already removed references to this list item, just
|
|
* free up the buffer_page and its page
|
|
*/
|
|
free_buffer_page(to_remove_page);
|
|
nr_removed--;
|
|
|
|
} while (to_remove_page != last_page);
|
|
|
|
RB_WARN_ON(cpu_buffer, nr_removed);
|
|
|
|
return nr_removed == 0;
|
|
}
|
|
|
|
static int
|
|
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *pages = &cpu_buffer->new_pages;
|
|
int retries, success;
|
|
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock);
|
|
/*
|
|
* We are holding the reader lock, so the reader page won't be swapped
|
|
* in the ring buffer. Now we are racing with the writer trying to
|
|
* move head page and the tail page.
|
|
* We are going to adapt the reader page update process where:
|
|
* 1. We first splice the start and end of list of new pages between
|
|
* the head page and its previous page.
|
|
* 2. We cmpxchg the prev_page->next to point from head page to the
|
|
* start of new pages list.
|
|
* 3. Finally, we update the head->prev to the end of new list.
|
|
*
|
|
* We will try this process 10 times, to make sure that we don't keep
|
|
* spinning.
|
|
*/
|
|
retries = 10;
|
|
success = 0;
|
|
while (retries--) {
|
|
struct list_head *head_page, *prev_page, *r;
|
|
struct list_head *last_page, *first_page;
|
|
struct list_head *head_page_with_bit;
|
|
|
|
head_page = &rb_set_head_page(cpu_buffer)->list;
|
|
if (!head_page)
|
|
break;
|
|
prev_page = head_page->prev;
|
|
|
|
first_page = pages->next;
|
|
last_page = pages->prev;
|
|
|
|
head_page_with_bit = (struct list_head *)
|
|
((unsigned long)head_page | RB_PAGE_HEAD);
|
|
|
|
last_page->next = head_page_with_bit;
|
|
first_page->prev = prev_page;
|
|
|
|
r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
|
|
|
|
if (r == head_page_with_bit) {
|
|
/*
|
|
* yay, we replaced the page pointer to our new list,
|
|
* now, we just have to update to head page's prev
|
|
* pointer to point to end of list
|
|
*/
|
|
head_page->prev = last_page;
|
|
success = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (success)
|
|
INIT_LIST_HEAD(pages);
|
|
/*
|
|
* If we weren't successful in adding in new pages, warn and stop
|
|
* tracing
|
|
*/
|
|
RB_WARN_ON(cpu_buffer, !success);
|
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
|
|
|
|
/* free pages if they weren't inserted */
|
|
if (!success) {
|
|
struct buffer_page *bpage, *tmp;
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
|
list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
}
|
|
return success;
|
|
}
|
|
|
|
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
int success;
|
|
|
|
if (cpu_buffer->nr_pages_to_update > 0)
|
|
success = rb_insert_pages(cpu_buffer);
|
|
else
|
|
success = rb_remove_pages(cpu_buffer,
|
|
-cpu_buffer->nr_pages_to_update);
|
|
|
|
if (success)
|
|
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
|
|
}
|
|
|
|
static void update_pages_handler(struct work_struct *work)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
|
|
struct ring_buffer_per_cpu, update_pages_work);
|
|
rb_update_pages(cpu_buffer);
|
|
complete(&cpu_buffer->update_done);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_resize - resize the ring buffer
|
|
* @buffer: the buffer to resize.
|
|
* @size: the new size.
|
|
* @cpu_id: the cpu buffer to resize
|
|
*
|
|
* Minimum size is 2 * BUF_PAGE_SIZE.
|
|
*
|
|
* Returns 0 on success and < 0 on failure.
|
|
*/
|
|
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
|
|
int cpu_id)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned nr_pages;
|
|
int cpu, err = 0;
|
|
|
|
/*
|
|
* Always succeed at resizing a non-existent buffer:
|
|
*/
|
|
if (!buffer)
|
|
return size;
|
|
|
|
/* Make sure the requested buffer exists */
|
|
if (cpu_id != RING_BUFFER_ALL_CPUS &&
|
|
!cpumask_test_cpu(cpu_id, buffer->cpumask))
|
|
return size;
|
|
|
|
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
size *= BUF_PAGE_SIZE;
|
|
|
|
/* we need a minimum of two pages */
|
|
if (size < BUF_PAGE_SIZE * 2)
|
|
size = BUF_PAGE_SIZE * 2;
|
|
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
|
|
/*
|
|
* Don't succeed if resizing is disabled, as a reader might be
|
|
* manipulating the ring buffer and is expecting a sane state while
|
|
* this is true.
|
|
*/
|
|
if (atomic_read(&buffer->resize_disabled))
|
|
return -EBUSY;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
if (cpu_id == RING_BUFFER_ALL_CPUS) {
|
|
/* calculate the pages to update */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
|
cpu_buffer->nr_pages;
|
|
/*
|
|
* nothing more to do for removing pages or no update
|
|
*/
|
|
if (cpu_buffer->nr_pages_to_update <= 0)
|
|
continue;
|
|
/*
|
|
* to add pages, make sure all new pages can be
|
|
* allocated without receiving ENOMEM
|
|
*/
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
|
|
&cpu_buffer->new_pages, cpu)) {
|
|
/* not enough memory for new pages */
|
|
err = -ENOMEM;
|
|
goto out_err;
|
|
}
|
|
}
|
|
|
|
get_online_cpus();
|
|
/*
|
|
* Fire off all the required work handlers
|
|
* We can't schedule on offline CPUs, but it's not necessary
|
|
* since we can change their buffer sizes without any race.
|
|
*/
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (!cpu_buffer->nr_pages_to_update)
|
|
continue;
|
|
|
|
/* The update must run on the CPU that is being updated. */
|
|
preempt_disable();
|
|
if (cpu == smp_processor_id() || !cpu_online(cpu)) {
|
|
rb_update_pages(cpu_buffer);
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
} else {
|
|
/*
|
|
* Can not disable preemption for schedule_work_on()
|
|
* on PREEMPT_RT.
|
|
*/
|
|
preempt_enable();
|
|
schedule_work_on(cpu,
|
|
&cpu_buffer->update_pages_work);
|
|
preempt_disable();
|
|
}
|
|
preempt_enable();
|
|
}
|
|
|
|
/* wait for all the updates to complete */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (!cpu_buffer->nr_pages_to_update)
|
|
continue;
|
|
|
|
if (cpu_online(cpu))
|
|
wait_for_completion(&cpu_buffer->update_done);
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
}
|
|
|
|
put_online_cpus();
|
|
} else {
|
|
/* Make sure this CPU has been intitialized */
|
|
if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu_id];
|
|
|
|
if (nr_pages == cpu_buffer->nr_pages)
|
|
goto out;
|
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
|
cpu_buffer->nr_pages;
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
if (cpu_buffer->nr_pages_to_update > 0 &&
|
|
__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
|
|
&cpu_buffer->new_pages, cpu_id)) {
|
|
err = -ENOMEM;
|
|
goto out_err;
|
|
}
|
|
|
|
get_online_cpus();
|
|
|
|
preempt_disable();
|
|
/* The update must run on the CPU that is being updated. */
|
|
if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
|
|
rb_update_pages(cpu_buffer);
|
|
else {
|
|
/*
|
|
* Can not disable preemption for schedule_work_on()
|
|
* on PREEMPT_RT.
|
|
*/
|
|
preempt_enable();
|
|
schedule_work_on(cpu_id,
|
|
&cpu_buffer->update_pages_work);
|
|
wait_for_completion(&cpu_buffer->update_done);
|
|
preempt_disable();
|
|
}
|
|
preempt_enable();
|
|
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
put_online_cpus();
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* The ring buffer resize can happen with the ring buffer
|
|
* enabled, so that the update disturbs the tracing as little
|
|
* as possible. But if the buffer is disabled, we do not need
|
|
* to worry about that, and we can take the time to verify
|
|
* that the buffer is not corrupt.
|
|
*/
|
|
if (atomic_read(&buffer->record_disabled)) {
|
|
atomic_inc(&buffer->record_disabled);
|
|
/*
|
|
* Even though the buffer was disabled, we must make sure
|
|
* that it is truly disabled before calling rb_check_pages.
|
|
* There could have been a race between checking
|
|
* record_disable and incrementing it.
|
|
*/
|
|
synchronize_sched();
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_check_pages(cpu_buffer);
|
|
}
|
|
atomic_dec(&buffer->record_disabled);
|
|
}
|
|
|
|
mutex_unlock(&buffer->mutex);
|
|
return size;
|
|
|
|
out_err:
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
|
|
if (list_empty(&cpu_buffer->new_pages))
|
|
continue;
|
|
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
|
list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
}
|
|
mutex_unlock(&buffer->mutex);
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_resize);
|
|
|
|
void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
|
|
{
|
|
mutex_lock(&buffer->mutex);
|
|
if (val)
|
|
buffer->flags |= RB_FL_OVERWRITE;
|
|
else
|
|
buffer->flags &= ~RB_FL_OVERWRITE;
|
|
mutex_unlock(&buffer->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
|
|
|
|
static inline void *
|
|
__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
|
|
{
|
|
return bpage->data + index;
|
|
}
|
|
|
|
static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
|
|
{
|
|
return bpage->page->data + index;
|
|
}
|
|
|
|
static inline struct ring_buffer_event *
|
|
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return __rb_page_index(cpu_buffer->reader_page,
|
|
cpu_buffer->reader_page->read);
|
|
}
|
|
|
|
static inline struct ring_buffer_event *
|
|
rb_iter_head_event(struct ring_buffer_iter *iter)
|
|
{
|
|
return __rb_page_index(iter->head_page, iter->head);
|
|
}
|
|
|
|
static inline unsigned rb_page_commit(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->page->commit);
|
|
}
|
|
|
|
/* Size is determined by what has been committed */
|
|
static inline unsigned rb_page_size(struct buffer_page *bpage)
|
|
{
|
|
return rb_page_commit(bpage);
|
|
}
|
|
|
|
static inline unsigned
|
|
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return rb_page_commit(cpu_buffer->commit_page);
|
|
}
|
|
|
|
static inline unsigned
|
|
rb_event_index(struct ring_buffer_event *event)
|
|
{
|
|
unsigned long addr = (unsigned long)event;
|
|
|
|
return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
|
|
}
|
|
|
|
static inline int
|
|
rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
unsigned long addr = (unsigned long)event;
|
|
unsigned long index;
|
|
|
|
index = rb_event_index(event);
|
|
addr &= PAGE_MASK;
|
|
|
|
return cpu_buffer->commit_page->page == (void *)addr &&
|
|
rb_commit_index(cpu_buffer) == index;
|
|
}
|
|
|
|
static void
|
|
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long max_count;
|
|
|
|
/*
|
|
* We only race with interrupts and NMIs on this CPU.
|
|
* If we own the commit event, then we can commit
|
|
* all others that interrupted us, since the interruptions
|
|
* are in stack format (they finish before they come
|
|
* back to us). This allows us to do a simple loop to
|
|
* assign the commit to the tail.
|
|
*/
|
|
again:
|
|
max_count = cpu_buffer->nr_pages * 100;
|
|
|
|
while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
|
|
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
|
|
return;
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_is_reader_page(cpu_buffer->tail_page)))
|
|
return;
|
|
local_set(&cpu_buffer->commit_page->page->commit,
|
|
rb_page_write(cpu_buffer->commit_page));
|
|
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
|
|
cpu_buffer->write_stamp =
|
|
cpu_buffer->commit_page->page->time_stamp;
|
|
/* add barrier to keep gcc from optimizing too much */
|
|
barrier();
|
|
}
|
|
while (rb_commit_index(cpu_buffer) !=
|
|
rb_page_write(cpu_buffer->commit_page)) {
|
|
|
|
local_set(&cpu_buffer->commit_page->page->commit,
|
|
rb_page_write(cpu_buffer->commit_page));
|
|
RB_WARN_ON(cpu_buffer,
|
|
local_read(&cpu_buffer->commit_page->page->commit) &
|
|
~RB_WRITE_MASK);
|
|
barrier();
|
|
}
|
|
|
|
/* again, keep gcc from optimizing */
|
|
barrier();
|
|
|
|
/*
|
|
* If an interrupt came in just after the first while loop
|
|
* and pushed the tail page forward, we will be left with
|
|
* a dangling commit that will never go forward.
|
|
*/
|
|
if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
|
|
goto again;
|
|
}
|
|
|
|
static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
|
|
cpu_buffer->reader_page->read = 0;
|
|
}
|
|
|
|
static void rb_inc_iter(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
|
|
/*
|
|
* The iterator could be on the reader page (it starts there).
|
|
* But the head could have moved, since the reader was
|
|
* found. Check for this case and assign the iterator
|
|
* to the head page instead of next.
|
|
*/
|
|
if (iter->head_page == cpu_buffer->reader_page)
|
|
iter->head_page = rb_set_head_page(cpu_buffer);
|
|
else
|
|
rb_inc_page(cpu_buffer, &iter->head_page);
|
|
|
|
iter->read_stamp = iter->head_page->page->time_stamp;
|
|
iter->head = 0;
|
|
}
|
|
|
|
/* Slow path, do not inline */
|
|
static noinline struct ring_buffer_event *
|
|
rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
|
|
{
|
|
event->type_len = RINGBUF_TYPE_TIME_EXTEND;
|
|
|
|
/* Not the first event on the page? */
|
|
if (rb_event_index(event)) {
|
|
event->time_delta = delta & TS_MASK;
|
|
event->array[0] = delta >> TS_SHIFT;
|
|
} else {
|
|
/* nope, just zero it */
|
|
event->time_delta = 0;
|
|
event->array[0] = 0;
|
|
}
|
|
|
|
return skip_time_extend(event);
|
|
}
|
|
|
|
/**
|
|
* rb_update_event - update event type and data
|
|
* @event: the even to update
|
|
* @type: the type of event
|
|
* @length: the size of the event field in the ring buffer
|
|
*
|
|
* Update the type and data fields of the event. The length
|
|
* is the actual size that is written to the ring buffer,
|
|
* and with this, we can determine what to place into the
|
|
* data field.
|
|
*/
|
|
static void
|
|
rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event, unsigned length,
|
|
int add_timestamp, u64 delta)
|
|
{
|
|
/* Only a commit updates the timestamp */
|
|
if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
|
|
delta = 0;
|
|
|
|
/*
|
|
* If we need to add a timestamp, then we
|
|
* add it to the start of the resevered space.
|
|
*/
|
|
if (unlikely(add_timestamp)) {
|
|
event = rb_add_time_stamp(event, delta);
|
|
length -= RB_LEN_TIME_EXTEND;
|
|
delta = 0;
|
|
}
|
|
|
|
event->time_delta = delta;
|
|
length -= RB_EVNT_HDR_SIZE;
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
|
|
event->type_len = 0;
|
|
event->array[0] = length;
|
|
} else
|
|
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
|
|
}
|
|
|
|
/*
|
|
* rb_handle_head_page - writer hit the head page
|
|
*
|
|
* Returns: +1 to retry page
|
|
* 0 to continue
|
|
* -1 on error
|
|
*/
|
|
static int
|
|
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *tail_page,
|
|
struct buffer_page *next_page)
|
|
{
|
|
struct buffer_page *new_head;
|
|
int entries;
|
|
int type;
|
|
int ret;
|
|
|
|
entries = rb_page_entries(next_page);
|
|
|
|
/*
|
|
* The hard part is here. We need to move the head
|
|
* forward, and protect against both readers on
|
|
* other CPUs and writers coming in via interrupts.
|
|
*/
|
|
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
|
|
RB_PAGE_HEAD);
|
|
|
|
/*
|
|
* type can be one of four:
|
|
* NORMAL - an interrupt already moved it for us
|
|
* HEAD - we are the first to get here.
|
|
* UPDATE - we are the interrupt interrupting
|
|
* a current move.
|
|
* MOVED - a reader on another CPU moved the next
|
|
* pointer to its reader page. Give up
|
|
* and try again.
|
|
*/
|
|
|
|
switch (type) {
|
|
case RB_PAGE_HEAD:
|
|
/*
|
|
* We changed the head to UPDATE, thus
|
|
* it is our responsibility to update
|
|
* the counters.
|
|
*/
|
|
local_add(entries, &cpu_buffer->overrun);
|
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
|
|
|
|
/*
|
|
* The entries will be zeroed out when we move the
|
|
* tail page.
|
|
*/
|
|
|
|
/* still more to do */
|
|
break;
|
|
|
|
case RB_PAGE_UPDATE:
|
|
/*
|
|
* This is an interrupt that interrupt the
|
|
* previous update. Still more to do.
|
|
*/
|
|
break;
|
|
case RB_PAGE_NORMAL:
|
|
/*
|
|
* An interrupt came in before the update
|
|
* and processed this for us.
|
|
* Nothing left to do.
|
|
*/
|
|
return 1;
|
|
case RB_PAGE_MOVED:
|
|
/*
|
|
* The reader is on another CPU and just did
|
|
* a swap with our next_page.
|
|
* Try again.
|
|
*/
|
|
return 1;
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* Now that we are here, the old head pointer is
|
|
* set to UPDATE. This will keep the reader from
|
|
* swapping the head page with the reader page.
|
|
* The reader (on another CPU) will spin till
|
|
* we are finished.
|
|
*
|
|
* We just need to protect against interrupts
|
|
* doing the job. We will set the next pointer
|
|
* to HEAD. After that, we set the old pointer
|
|
* to NORMAL, but only if it was HEAD before.
|
|
* otherwise we are an interrupt, and only
|
|
* want the outer most commit to reset it.
|
|
*/
|
|
new_head = next_page;
|
|
rb_inc_page(cpu_buffer, &new_head);
|
|
|
|
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
|
|
RB_PAGE_NORMAL);
|
|
|
|
/*
|
|
* Valid returns are:
|
|
* HEAD - an interrupt came in and already set it.
|
|
* NORMAL - One of two things:
|
|
* 1) We really set it.
|
|
* 2) A bunch of interrupts came in and moved
|
|
* the page forward again.
|
|
*/
|
|
switch (ret) {
|
|
case RB_PAGE_HEAD:
|
|
case RB_PAGE_NORMAL:
|
|
/* OK */
|
|
break;
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* It is possible that an interrupt came in,
|
|
* set the head up, then more interrupts came in
|
|
* and moved it again. When we get back here,
|
|
* the page would have been set to NORMAL but we
|
|
* just set it back to HEAD.
|
|
*
|
|
* How do you detect this? Well, if that happened
|
|
* the tail page would have moved.
|
|
*/
|
|
if (ret == RB_PAGE_NORMAL) {
|
|
/*
|
|
* If the tail had moved passed next, then we need
|
|
* to reset the pointer.
|
|
*/
|
|
if (cpu_buffer->tail_page != tail_page &&
|
|
cpu_buffer->tail_page != next_page)
|
|
rb_head_page_set_normal(cpu_buffer, new_head,
|
|
next_page,
|
|
RB_PAGE_HEAD);
|
|
}
|
|
|
|
/*
|
|
* If this was the outer most commit (the one that
|
|
* changed the original pointer from HEAD to UPDATE),
|
|
* then it is up to us to reset it to NORMAL.
|
|
*/
|
|
if (type == RB_PAGE_HEAD) {
|
|
ret = rb_head_page_set_normal(cpu_buffer, next_page,
|
|
tail_page,
|
|
RB_PAGE_UPDATE);
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
ret != RB_PAGE_UPDATE))
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static unsigned rb_calculate_event_length(unsigned length)
|
|
{
|
|
struct ring_buffer_event event; /* Used only for sizeof array */
|
|
|
|
/* zero length can cause confusions */
|
|
if (!length)
|
|
length = 1;
|
|
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
|
|
length += sizeof(event.array[0]);
|
|
|
|
length += RB_EVNT_HDR_SIZE;
|
|
length = ALIGN(length, RB_ARCH_ALIGNMENT);
|
|
|
|
return length;
|
|
}
|
|
|
|
static inline void
|
|
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *tail_page,
|
|
unsigned long tail, unsigned long length)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
|
|
/*
|
|
* Only the event that crossed the page boundary
|
|
* must fill the old tail_page with padding.
|
|
*/
|
|
if (tail >= BUF_PAGE_SIZE) {
|
|
/*
|
|
* If the page was filled, then we still need
|
|
* to update the real_end. Reset it to zero
|
|
* and the reader will ignore it.
|
|
*/
|
|
if (tail == BUF_PAGE_SIZE)
|
|
tail_page->real_end = 0;
|
|
|
|
local_sub(length, &tail_page->write);
|
|
return;
|
|
}
|
|
|
|
event = __rb_page_index(tail_page, tail);
|
|
kmemcheck_annotate_bitfield(event, bitfield);
|
|
|
|
/* account for padding bytes */
|
|
local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
|
|
|
|
/*
|
|
* Save the original length to the meta data.
|
|
* This will be used by the reader to add lost event
|
|
* counter.
|
|
*/
|
|
tail_page->real_end = tail;
|
|
|
|
/*
|
|
* If this event is bigger than the minimum size, then
|
|
* we need to be careful that we don't subtract the
|
|
* write counter enough to allow another writer to slip
|
|
* in on this page.
|
|
* We put in a discarded commit instead, to make sure
|
|
* that this space is not used again.
|
|
*
|
|
* If we are less than the minimum size, we don't need to
|
|
* worry about it.
|
|
*/
|
|
if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
|
|
/* No room for any events */
|
|
|
|
/* Mark the rest of the page with padding */
|
|
rb_event_set_padding(event);
|
|
|
|
/* Set the write back to the previous setting */
|
|
local_sub(length, &tail_page->write);
|
|
return;
|
|
}
|
|
|
|
/* Put in a discarded event */
|
|
event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
|
|
event->type_len = RINGBUF_TYPE_PADDING;
|
|
/* time delta must be non zero */
|
|
event->time_delta = 1;
|
|
|
|
/* Set write to end of buffer */
|
|
length = (tail + length) - BUF_PAGE_SIZE;
|
|
local_sub(length, &tail_page->write);
|
|
}
|
|
|
|
/*
|
|
* This is the slow path, force gcc not to inline it.
|
|
*/
|
|
static noinline struct ring_buffer_event *
|
|
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long length, unsigned long tail,
|
|
struct buffer_page *tail_page, u64 ts)
|
|
{
|
|
struct buffer_page *commit_page = cpu_buffer->commit_page;
|
|
struct ring_buffer *buffer = cpu_buffer->buffer;
|
|
struct buffer_page *next_page;
|
|
int ret;
|
|
|
|
next_page = tail_page;
|
|
|
|
rb_inc_page(cpu_buffer, &next_page);
|
|
|
|
/*
|
|
* If for some reason, we had an interrupt storm that made
|
|
* it all the way around the buffer, bail, and warn
|
|
* about it.
|
|
*/
|
|
if (unlikely(next_page == commit_page)) {
|
|
local_inc(&cpu_buffer->commit_overrun);
|
|
goto out_reset;
|
|
}
|
|
|
|
/*
|
|
* This is where the fun begins!
|
|
*
|
|
* We are fighting against races between a reader that
|
|
* could be on another CPU trying to swap its reader
|
|
* page with the buffer head.
|
|
*
|
|
* We are also fighting against interrupts coming in and
|
|
* moving the head or tail on us as well.
|
|
*
|
|
* If the next page is the head page then we have filled
|
|
* the buffer, unless the commit page is still on the
|
|
* reader page.
|
|
*/
|
|
if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
|
|
|
|
/*
|
|
* If the commit is not on the reader page, then
|
|
* move the header page.
|
|
*/
|
|
if (!rb_is_reader_page(cpu_buffer->commit_page)) {
|
|
/*
|
|
* If we are not in overwrite mode,
|
|
* this is easy, just stop here.
|
|
*/
|
|
if (!(buffer->flags & RB_FL_OVERWRITE)) {
|
|
local_inc(&cpu_buffer->dropped_events);
|
|
goto out_reset;
|
|
}
|
|
|
|
ret = rb_handle_head_page(cpu_buffer,
|
|
tail_page,
|
|
next_page);
|
|
if (ret < 0)
|
|
goto out_reset;
|
|
if (ret)
|
|
goto out_again;
|
|
} else {
|
|
/*
|
|
* We need to be careful here too. The
|
|
* commit page could still be on the reader
|
|
* page. We could have a small buffer, and
|
|
* have filled up the buffer with events
|
|
* from interrupts and such, and wrapped.
|
|
*
|
|
* Note, if the tail page is also the on the
|
|
* reader_page, we let it move out.
|
|
*/
|
|
if (unlikely((cpu_buffer->commit_page !=
|
|
cpu_buffer->tail_page) &&
|
|
(cpu_buffer->commit_page ==
|
|
cpu_buffer->reader_page))) {
|
|
local_inc(&cpu_buffer->commit_overrun);
|
|
goto out_reset;
|
|
}
|
|
}
|
|
}
|
|
|
|
ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
|
|
if (ret) {
|
|
/*
|
|
* Nested commits always have zero deltas, so
|
|
* just reread the time stamp
|
|
*/
|
|
ts = rb_time_stamp(buffer);
|
|
next_page->page->time_stamp = ts;
|
|
}
|
|
|
|
out_again:
|
|
|
|
rb_reset_tail(cpu_buffer, tail_page, tail, length);
|
|
|
|
/* fail and let the caller try again */
|
|
return ERR_PTR(-EAGAIN);
|
|
|
|
out_reset:
|
|
/* reset write */
|
|
rb_reset_tail(cpu_buffer, tail_page, tail, length);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long length, u64 ts,
|
|
u64 delta, int add_timestamp)
|
|
{
|
|
struct buffer_page *tail_page;
|
|
struct ring_buffer_event *event;
|
|
unsigned long tail, write;
|
|
|
|
/*
|
|
* If the time delta since the last event is too big to
|
|
* hold in the time field of the event, then we append a
|
|
* TIME EXTEND event ahead of the data event.
|
|
*/
|
|
if (unlikely(add_timestamp))
|
|
length += RB_LEN_TIME_EXTEND;
|
|
|
|
tail_page = cpu_buffer->tail_page;
|
|
write = local_add_return(length, &tail_page->write);
|
|
|
|
/* set write to only the index of the write */
|
|
write &= RB_WRITE_MASK;
|
|
tail = write - length;
|
|
|
|
/*
|
|
* If this is the first commit on the page, then it has the same
|
|
* timestamp as the page itself.
|
|
*/
|
|
if (!tail)
|
|
delta = 0;
|
|
|
|
/* See if we shot pass the end of this buffer page */
|
|
if (unlikely(write > BUF_PAGE_SIZE))
|
|
return rb_move_tail(cpu_buffer, length, tail,
|
|
tail_page, ts);
|
|
|
|
/* We reserved something on the buffer */
|
|
|
|
event = __rb_page_index(tail_page, tail);
|
|
kmemcheck_annotate_bitfield(event, bitfield);
|
|
rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
|
|
|
|
local_inc(&tail_page->entries);
|
|
|
|
/*
|
|
* If this is the first commit on the page, then update
|
|
* its timestamp.
|
|
*/
|
|
if (!tail)
|
|
tail_page->page->time_stamp = ts;
|
|
|
|
/* account for these added bytes */
|
|
local_add(length, &cpu_buffer->entries_bytes);
|
|
|
|
return event;
|
|
}
|
|
|
|
static inline int
|
|
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
unsigned long new_index, old_index;
|
|
struct buffer_page *bpage;
|
|
unsigned long index;
|
|
unsigned long addr;
|
|
|
|
new_index = rb_event_index(event);
|
|
old_index = new_index + rb_event_ts_length(event);
|
|
addr = (unsigned long)event;
|
|
addr &= PAGE_MASK;
|
|
|
|
bpage = cpu_buffer->tail_page;
|
|
|
|
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
|
|
unsigned long write_mask =
|
|
local_read(&bpage->write) & ~RB_WRITE_MASK;
|
|
unsigned long event_length = rb_event_length(event);
|
|
/*
|
|
* This is on the tail page. It is possible that
|
|
* a write could come in and move the tail page
|
|
* and write to the next page. That is fine
|
|
* because we just shorten what is on this page.
|
|
*/
|
|
old_index += write_mask;
|
|
new_index += write_mask;
|
|
index = local_cmpxchg(&bpage->write, old_index, new_index);
|
|
if (index == old_index) {
|
|
/* update counters */
|
|
local_sub(event_length, &cpu_buffer->entries_bytes);
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
/* could not discard */
|
|
return 0;
|
|
}
|
|
|
|
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
local_inc(&cpu_buffer->committing);
|
|
local_inc(&cpu_buffer->commits);
|
|
}
|
|
|
|
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long commits;
|
|
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
!local_read(&cpu_buffer->committing)))
|
|
return;
|
|
|
|
again:
|
|
commits = local_read(&cpu_buffer->commits);
|
|
/* synchronize with interrupts */
|
|
barrier();
|
|
if (local_read(&cpu_buffer->committing) == 1)
|
|
rb_set_commit_to_write(cpu_buffer);
|
|
|
|
local_dec(&cpu_buffer->committing);
|
|
|
|
/* synchronize with interrupts */
|
|
barrier();
|
|
|
|
/*
|
|
* Need to account for interrupts coming in between the
|
|
* updating of the commit page and the clearing of the
|
|
* committing counter.
|
|
*/
|
|
if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
|
|
!local_read(&cpu_buffer->committing)) {
|
|
local_inc(&cpu_buffer->committing);
|
|
goto again;
|
|
}
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_reserve_next_event(struct ring_buffer *buffer,
|
|
struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long length)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
u64 ts, delta;
|
|
int nr_loops = 0;
|
|
int add_timestamp;
|
|
u64 diff;
|
|
|
|
rb_start_commit(cpu_buffer);
|
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
|
/*
|
|
* Due to the ability to swap a cpu buffer from a buffer
|
|
* it is possible it was swapped before we committed.
|
|
* (committing stops a swap). We check for it here and
|
|
* if it happened, we have to fail the write.
|
|
*/
|
|
barrier();
|
|
if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
|
|
local_dec(&cpu_buffer->committing);
|
|
local_dec(&cpu_buffer->commits);
|
|
return NULL;
|
|
}
|
|
#endif
|
|
|
|
length = rb_calculate_event_length(length);
|
|
again:
|
|
add_timestamp = 0;
|
|
delta = 0;
|
|
|
|
/*
|
|
* We allow for interrupts to reenter here and do a trace.
|
|
* If one does, it will cause this original code to loop
|
|
* back here. Even with heavy interrupts happening, this
|
|
* should only happen a few times in a row. If this happens
|
|
* 1000 times in a row, there must be either an interrupt
|
|
* storm or we have something buggy.
|
|
* Bail!
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
|
|
goto out_fail;
|
|
|
|
ts = rb_time_stamp(cpu_buffer->buffer);
|
|
diff = ts - cpu_buffer->write_stamp;
|
|
|
|
/* make sure this diff is calculated here */
|
|
barrier();
|
|
|
|
/* Did the write stamp get updated already? */
|
|
if (likely(ts >= cpu_buffer->write_stamp)) {
|
|
delta = diff;
|
|
if (unlikely(test_time_stamp(delta))) {
|
|
int local_clock_stable = 1;
|
|
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
|
|
local_clock_stable = sched_clock_stable();
|
|
#endif
|
|
WARN_ONCE(delta > (1ULL << 59),
|
|
KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
|
|
(unsigned long long)delta,
|
|
(unsigned long long)ts,
|
|
(unsigned long long)cpu_buffer->write_stamp,
|
|
local_clock_stable ? "" :
|
|
"If you just came from a suspend/resume,\n"
|
|
"please switch to the trace global clock:\n"
|
|
" echo global > /sys/kernel/debug/tracing/trace_clock\n");
|
|
add_timestamp = 1;
|
|
}
|
|
}
|
|
|
|
event = __rb_reserve_next(cpu_buffer, length, ts,
|
|
delta, add_timestamp);
|
|
if (unlikely(PTR_ERR(event) == -EAGAIN))
|
|
goto again;
|
|
|
|
if (!event)
|
|
goto out_fail;
|
|
|
|
return event;
|
|
|
|
out_fail:
|
|
rb_end_commit(cpu_buffer);
|
|
return NULL;
|
|
}
|
|
|
|
#ifdef CONFIG_TRACING
|
|
|
|
/*
|
|
* The lock and unlock are done within a preempt disable section.
|
|
* The current_context per_cpu variable can only be modified
|
|
* by the current task between lock and unlock. But it can
|
|
* be modified more than once via an interrupt. To pass this
|
|
* information from the lock to the unlock without having to
|
|
* access the 'in_interrupt()' functions again (which do show
|
|
* a bit of overhead in something as critical as function tracing,
|
|
* we use a bitmask trick.
|
|
*
|
|
* bit 0 = NMI context
|
|
* bit 1 = IRQ context
|
|
* bit 2 = SoftIRQ context
|
|
* bit 3 = normal context.
|
|
*
|
|
* This works because this is the order of contexts that can
|
|
* preempt other contexts. A SoftIRQ never preempts an IRQ
|
|
* context.
|
|
*
|
|
* When the context is determined, the corresponding bit is
|
|
* checked and set (if it was set, then a recursion of that context
|
|
* happened).
|
|
*
|
|
* On unlock, we need to clear this bit. To do so, just subtract
|
|
* 1 from the current_context and AND it to itself.
|
|
*
|
|
* (binary)
|
|
* 101 - 1 = 100
|
|
* 101 & 100 = 100 (clearing bit zero)
|
|
*
|
|
* 1010 - 1 = 1001
|
|
* 1010 & 1001 = 1000 (clearing bit 1)
|
|
*
|
|
* The least significant bit can be cleared this way, and it
|
|
* just so happens that it is the same bit corresponding to
|
|
* the current context.
|
|
*/
|
|
static DEFINE_PER_CPU(unsigned int, current_context);
|
|
|
|
static __always_inline int trace_recursive_lock(void)
|
|
{
|
|
unsigned int val = this_cpu_read(current_context);
|
|
int bit;
|
|
|
|
if (in_interrupt()) {
|
|
if (in_nmi())
|
|
bit = 0;
|
|
else if (in_irq())
|
|
bit = 1;
|
|
else
|
|
bit = 2;
|
|
} else
|
|
bit = 3;
|
|
|
|
if (unlikely(val & (1 << bit)))
|
|
return 1;
|
|
|
|
val |= (1 << bit);
|
|
this_cpu_write(current_context, val);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __always_inline void trace_recursive_unlock(void)
|
|
{
|
|
unsigned int val = this_cpu_read(current_context);
|
|
|
|
val--;
|
|
val &= this_cpu_read(current_context);
|
|
this_cpu_write(current_context, val);
|
|
}
|
|
|
|
#else
|
|
|
|
#define trace_recursive_lock() (0)
|
|
#define trace_recursive_unlock() do { } while (0)
|
|
|
|
#endif
|
|
|
|
/**
|
|
* ring_buffer_lock_reserve - reserve a part of the buffer
|
|
* @buffer: the ring buffer to reserve from
|
|
* @length: the length of the data to reserve (excluding event header)
|
|
*
|
|
* Returns a reseverd event on the ring buffer to copy directly to.
|
|
* The user of this interface will need to get the body to write into
|
|
* and can use the ring_buffer_event_data() interface.
|
|
*
|
|
* The length is the length of the data needed, not the event length
|
|
* which also includes the event header.
|
|
*
|
|
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
|
|
* If NULL is returned, then nothing has been allocated or locked.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int cpu;
|
|
|
|
if (ring_buffer_flags != RB_BUFFERS_ON)
|
|
return NULL;
|
|
|
|
/* If we are tracing schedule, we don't want to recurse */
|
|
preempt_disable_notrace();
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
goto out_nocheck;
|
|
|
|
if (trace_recursive_lock())
|
|
goto out_nocheck;
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
|
goto out;
|
|
|
|
if (length > BUF_MAX_DATA_SIZE)
|
|
goto out;
|
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
|
if (!event)
|
|
goto out;
|
|
|
|
return event;
|
|
|
|
out:
|
|
trace_recursive_unlock();
|
|
|
|
out_nocheck:
|
|
preempt_enable_notrace();
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
|
|
|
|
static void
|
|
rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
/*
|
|
* The event first in the commit queue updates the
|
|
* time stamp.
|
|
*/
|
|
if (rb_event_is_commit(cpu_buffer, event)) {
|
|
/*
|
|
* A commit event that is first on a page
|
|
* updates the write timestamp with the page stamp
|
|
*/
|
|
if (!rb_event_index(event))
|
|
cpu_buffer->write_stamp =
|
|
cpu_buffer->commit_page->page->time_stamp;
|
|
else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
|
|
delta = event->array[0];
|
|
delta <<= TS_SHIFT;
|
|
delta += event->time_delta;
|
|
cpu_buffer->write_stamp += delta;
|
|
} else
|
|
cpu_buffer->write_stamp += event->time_delta;
|
|
}
|
|
}
|
|
|
|
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
local_inc(&cpu_buffer->entries);
|
|
rb_update_write_stamp(cpu_buffer, event);
|
|
rb_end_commit(cpu_buffer);
|
|
}
|
|
|
|
static __always_inline void
|
|
rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
if (buffer->irq_work.waiters_pending) {
|
|
buffer->irq_work.waiters_pending = false;
|
|
/* irq_work_queue() supplies it's own memory barriers */
|
|
irq_work_queue(&buffer->irq_work.work);
|
|
}
|
|
|
|
if (cpu_buffer->irq_work.waiters_pending) {
|
|
cpu_buffer->irq_work.waiters_pending = false;
|
|
/* irq_work_queue() supplies it's own memory barriers */
|
|
irq_work_queue(&cpu_buffer->irq_work.work);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_unlock_commit - commit a reserved
|
|
* @buffer: The buffer to commit to
|
|
* @event: The event pointer to commit.
|
|
*
|
|
* This commits the data to the ring buffer, and releases any locks held.
|
|
*
|
|
* Must be paired with ring_buffer_lock_reserve.
|
|
*/
|
|
int ring_buffer_unlock_commit(struct ring_buffer *buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu = raw_smp_processor_id();
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
rb_commit(cpu_buffer, event);
|
|
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
|
|
trace_recursive_unlock();
|
|
|
|
preempt_enable_notrace();
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
|
|
|
|
static inline void rb_event_discard(struct ring_buffer_event *event)
|
|
{
|
|
if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
|
|
event = skip_time_extend(event);
|
|
|
|
/* array[0] holds the actual length for the discarded event */
|
|
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
|
|
event->type_len = RINGBUF_TYPE_PADDING;
|
|
/* time delta must be non zero */
|
|
if (!event->time_delta)
|
|
event->time_delta = 1;
|
|
}
|
|
|
|
/*
|
|
* Decrement the entries to the page that an event is on.
|
|
* The event does not even need to exist, only the pointer
|
|
* to the page it is on. This may only be called before the commit
|
|
* takes place.
|
|
*/
|
|
static inline void
|
|
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
unsigned long addr = (unsigned long)event;
|
|
struct buffer_page *bpage = cpu_buffer->commit_page;
|
|
struct buffer_page *start;
|
|
|
|
addr &= PAGE_MASK;
|
|
|
|
/* Do the likely case first */
|
|
if (likely(bpage->page == (void *)addr)) {
|
|
local_dec(&bpage->entries);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Because the commit page may be on the reader page we
|
|
* start with the next page and check the end loop there.
|
|
*/
|
|
rb_inc_page(cpu_buffer, &bpage);
|
|
start = bpage;
|
|
do {
|
|
if (bpage->page == (void *)addr) {
|
|
local_dec(&bpage->entries);
|
|
return;
|
|
}
|
|
rb_inc_page(cpu_buffer, &bpage);
|
|
} while (bpage != start);
|
|
|
|
/* commit not part of this buffer?? */
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_commit_discard - discard an event that has not been committed
|
|
* @buffer: the ring buffer
|
|
* @event: non committed event to discard
|
|
*
|
|
* Sometimes an event that is in the ring buffer needs to be ignored.
|
|
* This function lets the user discard an event in the ring buffer
|
|
* and then that event will not be read later.
|
|
*
|
|
* This function only works if it is called before the the item has been
|
|
* committed. It will try to free the event from the ring buffer
|
|
* if another event has not been added behind it.
|
|
*
|
|
* If another event has been added behind it, it will set the event
|
|
* up as discarded, and perform the commit.
|
|
*
|
|
* If this function is called, do not call ring_buffer_unlock_commit on
|
|
* the event.
|
|
*/
|
|
void ring_buffer_discard_commit(struct ring_buffer *buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* The event is discarded regardless */
|
|
rb_event_discard(event);
|
|
|
|
cpu = smp_processor_id();
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
/*
|
|
* This must only be called if the event has not been
|
|
* committed yet. Thus we can assume that preemption
|
|
* is still disabled.
|
|
*/
|
|
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
|
|
|
|
rb_decrement_entry(cpu_buffer, event);
|
|
if (rb_try_to_discard(cpu_buffer, event))
|
|
goto out;
|
|
|
|
/*
|
|
* The commit is still visible by the reader, so we
|
|
* must still update the timestamp.
|
|
*/
|
|
rb_update_write_stamp(cpu_buffer, event);
|
|
out:
|
|
rb_end_commit(cpu_buffer);
|
|
|
|
trace_recursive_unlock();
|
|
|
|
preempt_enable_notrace();
|
|
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
|
|
|
|
/**
|
|
* ring_buffer_write - write data to the buffer without reserving
|
|
* @buffer: The ring buffer to write to.
|
|
* @length: The length of the data being written (excluding the event header)
|
|
* @data: The data to write to the buffer.
|
|
*
|
|
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
|
|
* one function. If you already have the data to write to the buffer, it
|
|
* may be easier to simply call this function.
|
|
*
|
|
* Note, like ring_buffer_lock_reserve, the length is the length of the data
|
|
* and not the length of the event which would hold the header.
|
|
*/
|
|
int ring_buffer_write(struct ring_buffer *buffer,
|
|
unsigned long length,
|
|
void *data)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
void *body;
|
|
int ret = -EBUSY;
|
|
int cpu;
|
|
|
|
if (ring_buffer_flags != RB_BUFFERS_ON)
|
|
return -EBUSY;
|
|
|
|
preempt_disable_notrace();
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
goto out;
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
|
goto out;
|
|
|
|
if (length > BUF_MAX_DATA_SIZE)
|
|
goto out;
|
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
|
if (!event)
|
|
goto out;
|
|
|
|
body = rb_event_data(event);
|
|
|
|
memcpy(body, data, length);
|
|
|
|
rb_commit(cpu_buffer, event);
|
|
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
|
|
ret = 0;
|
|
out:
|
|
preempt_enable_notrace();
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_write);
|
|
|
|
static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *reader = cpu_buffer->reader_page;
|
|
struct buffer_page *head = rb_set_head_page(cpu_buffer);
|
|
struct buffer_page *commit = cpu_buffer->commit_page;
|
|
|
|
/* In case of error, head will be NULL */
|
|
if (unlikely(!head))
|
|
return 1;
|
|
|
|
return reader->read == rb_page_commit(reader) &&
|
|
(commit == reader ||
|
|
(commit == head &&
|
|
head->read == rb_page_commit(commit)));
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_record_disable - stop all writes into the buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* The caller should call synchronize_sched() after this.
|
|
*/
|
|
void ring_buffer_record_disable(struct ring_buffer *buffer)
|
|
{
|
|
atomic_inc(&buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
|
|
|
|
/**
|
|
* ring_buffer_record_enable - enable writes to the buffer
|
|
* @buffer: The ring buffer to enable writes
|
|
*
|
|
* Note, multiple disables will need the same number of enables
|
|
* to truly enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable(struct ring_buffer *buffer)
|
|
{
|
|
atomic_dec(&buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
|
|
|
|
/**
|
|
* ring_buffer_record_off - stop all writes into the buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* This is different than ring_buffer_record_disable() as
|
|
* it works like an on/off switch, where as the disable() version
|
|
* must be paired with a enable().
|
|
*/
|
|
void ring_buffer_record_off(struct ring_buffer *buffer)
|
|
{
|
|
unsigned int rd;
|
|
unsigned int new_rd;
|
|
|
|
do {
|
|
rd = atomic_read(&buffer->record_disabled);
|
|
new_rd = rd | RB_BUFFER_OFF;
|
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_off);
|
|
|
|
/**
|
|
* ring_buffer_record_on - restart writes into the buffer
|
|
* @buffer: The ring buffer to start writes to.
|
|
*
|
|
* This enables all writes to the buffer that was disabled by
|
|
* ring_buffer_record_off().
|
|
*
|
|
* This is different than ring_buffer_record_enable() as
|
|
* it works like an on/off switch, where as the enable() version
|
|
* must be paired with a disable().
|
|
*/
|
|
void ring_buffer_record_on(struct ring_buffer *buffer)
|
|
{
|
|
unsigned int rd;
|
|
unsigned int new_rd;
|
|
|
|
do {
|
|
rd = atomic_read(&buffer->record_disabled);
|
|
new_rd = rd & ~RB_BUFFER_OFF;
|
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_on);
|
|
|
|
/**
|
|
* ring_buffer_record_is_on - return true if the ring buffer can write
|
|
* @buffer: The ring buffer to see if write is enabled
|
|
*
|
|
* Returns true if the ring buffer is in a state that it accepts writes.
|
|
*/
|
|
int ring_buffer_record_is_on(struct ring_buffer *buffer)
|
|
{
|
|
return !atomic_read(&buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
* @cpu: The CPU buffer to stop
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* The caller should call synchronize_sched() after this.
|
|
*/
|
|
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
|
|
|
|
/**
|
|
* ring_buffer_record_enable_cpu - enable writes to the buffer
|
|
* @buffer: The ring buffer to enable writes
|
|
* @cpu: The CPU to enable.
|
|
*
|
|
* Note, multiple disables will need the same number of enables
|
|
* to truly enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
|
|
|
|
/*
|
|
* The total entries in the ring buffer is the running counter
|
|
* of entries entered into the ring buffer, minus the sum of
|
|
* the entries read from the ring buffer and the number of
|
|
* entries that were overwritten.
|
|
*/
|
|
static inline unsigned long
|
|
rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return local_read(&cpu_buffer->entries) -
|
|
(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to read from.
|
|
*/
|
|
u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
unsigned long flags;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *bpage;
|
|
u64 ret = 0;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
/*
|
|
* if the tail is on reader_page, oldest time stamp is on the reader
|
|
* page
|
|
*/
|
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
|
bpage = cpu_buffer->reader_page;
|
|
else
|
|
bpage = rb_set_head_page(cpu_buffer);
|
|
if (bpage)
|
|
ret = bpage->page->time_stamp;
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
|
|
|
|
/**
|
|
* ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to read from.
|
|
*/
|
|
unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
|
|
|
|
/**
|
|
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the entries from.
|
|
*/
|
|
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
return rb_num_of_entries(cpu_buffer);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
|
|
|
|
/**
|
|
* ring_buffer_overrun_cpu - get the number of overruns caused by the ring
|
|
* buffer wrapping around (only if RB_FL_OVERWRITE is on).
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->overrun);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
|
|
|
|
/**
|
|
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by
|
|
* commits failing due to the buffer wrapping around while there are uncommitted
|
|
* events, such as during an interrupt storm.
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long
|
|
ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->commit_overrun);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
|
|
|
|
/**
|
|
* ring_buffer_dropped_events_cpu - get the number of dropped events caused by
|
|
* the ring buffer filling up (only if RB_FL_OVERWRITE is off).
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long
|
|
ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->dropped_events);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
|
|
|
|
/**
|
|
* ring_buffer_read_events_cpu - get the number of events successfully read
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of events read
|
|
*/
|
|
unsigned long
|
|
ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return cpu_buffer->read;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
|
|
|
|
/**
|
|
* ring_buffer_entries - get the number of entries in a buffer
|
|
* @buffer: The ring buffer
|
|
*
|
|
* Returns the total number of entries in the ring buffer
|
|
* (all CPU entries)
|
|
*/
|
|
unsigned long ring_buffer_entries(struct ring_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long entries = 0;
|
|
int cpu;
|
|
|
|
/* if you care about this being correct, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
entries += rb_num_of_entries(cpu_buffer);
|
|
}
|
|
|
|
return entries;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_entries);
|
|
|
|
/**
|
|
* ring_buffer_overruns - get the number of overruns in buffer
|
|
* @buffer: The ring buffer
|
|
*
|
|
* Returns the total number of overruns in the ring buffer
|
|
* (all CPU entries)
|
|
*/
|
|
unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long overruns = 0;
|
|
int cpu;
|
|
|
|
/* if you care about this being correct, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
overruns += local_read(&cpu_buffer->overrun);
|
|
}
|
|
|
|
return overruns;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
|
|
|
|
static void rb_iter_reset(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
|
|
/* Iterator usage is expected to have record disabled */
|
|
if (list_empty(&cpu_buffer->reader_page->list)) {
|
|
iter->head_page = rb_set_head_page(cpu_buffer);
|
|
if (unlikely(!iter->head_page))
|
|
return;
|
|
iter->head = iter->head_page->read;
|
|
} else {
|
|
iter->head_page = cpu_buffer->reader_page;
|
|
iter->head = cpu_buffer->reader_page->read;
|
|
}
|
|
if (iter->head)
|
|
iter->read_stamp = cpu_buffer->read_stamp;
|
|
else
|
|
iter->read_stamp = iter->head_page->page->time_stamp;
|
|
iter->cache_reader_page = cpu_buffer->reader_page;
|
|
iter->cache_read = cpu_buffer->read;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_iter_reset - reset an iterator
|
|
* @iter: The iterator to reset
|
|
*
|
|
* Resets the iterator, so that it will start from the beginning
|
|
* again.
|
|
*/
|
|
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
if (!iter)
|
|
return;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_iter_reset(iter);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
|
|
|
|
/**
|
|
* ring_buffer_iter_empty - check if an iterator has no more to read
|
|
* @iter: The iterator to check
|
|
*/
|
|
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
return iter->head_page == cpu_buffer->commit_page &&
|
|
iter->head == rb_commit_index(cpu_buffer);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
|
|
|
|
static void
|
|
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = event->array[0];
|
|
delta <<= TS_SHIFT;
|
|
delta += event->time_delta;
|
|
cpu_buffer->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
cpu_buffer->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
return;
|
|
}
|
|
|
|
static void
|
|
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = event->array[0];
|
|
delta <<= TS_SHIFT;
|
|
delta += event->time_delta;
|
|
iter->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
iter->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
return;
|
|
}
|
|
|
|
static struct buffer_page *
|
|
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *reader = NULL;
|
|
unsigned long overwrite;
|
|
unsigned long flags;
|
|
int nr_loops = 0;
|
|
int ret;
|
|
|
|
local_irq_save(flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
again:
|
|
/*
|
|
* This should normally only loop twice. But because the
|
|
* start of the reader inserts an empty page, it causes
|
|
* a case where we will loop three times. There should be no
|
|
* reason to loop four times (that I know of).
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
|
|
reader = NULL;
|
|
goto out;
|
|
}
|
|
|
|
reader = cpu_buffer->reader_page;
|
|
|
|
/* If there's more to read, return this page */
|
|
if (cpu_buffer->reader_page->read < rb_page_size(reader))
|
|
goto out;
|
|
|
|
/* Never should we have an index greater than the size */
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
cpu_buffer->reader_page->read > rb_page_size(reader)))
|
|
goto out;
|
|
|
|
/* check if we caught up to the tail */
|
|
reader = NULL;
|
|
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
|
|
goto out;
|
|
|
|
/* Don't bother swapping if the ring buffer is empty */
|
|
if (rb_num_of_entries(cpu_buffer) == 0)
|
|
goto out;
|
|
|
|
/*
|
|
* Reset the reader page to size zero.
|
|
*/
|
|
local_set(&cpu_buffer->reader_page->write, 0);
|
|
local_set(&cpu_buffer->reader_page->entries, 0);
|
|
local_set(&cpu_buffer->reader_page->page->commit, 0);
|
|
cpu_buffer->reader_page->real_end = 0;
|
|
|
|
spin:
|
|
/*
|
|
* Splice the empty reader page into the list around the head.
|
|
*/
|
|
reader = rb_set_head_page(cpu_buffer);
|
|
if (!reader)
|
|
goto out;
|
|
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
|
|
cpu_buffer->reader_page->list.prev = reader->list.prev;
|
|
|
|
/*
|
|
* cpu_buffer->pages just needs to point to the buffer, it
|
|
* has no specific buffer page to point to. Lets move it out
|
|
* of our way so we don't accidentally swap it.
|
|
*/
|
|
cpu_buffer->pages = reader->list.prev;
|
|
|
|
/* The reader page will be pointing to the new head */
|
|
rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
|
|
|
|
/*
|
|
* We want to make sure we read the overruns after we set up our
|
|
* pointers to the next object. The writer side does a
|
|
* cmpxchg to cross pages which acts as the mb on the writer
|
|
* side. Note, the reader will constantly fail the swap
|
|
* while the writer is updating the pointers, so this
|
|
* guarantees that the overwrite recorded here is the one we
|
|
* want to compare with the last_overrun.
|
|
*/
|
|
smp_mb();
|
|
overwrite = local_read(&(cpu_buffer->overrun));
|
|
|
|
/*
|
|
* Here's the tricky part.
|
|
*
|
|
* We need to move the pointer past the header page.
|
|
* But we can only do that if a writer is not currently
|
|
* moving it. The page before the header page has the
|
|
* flag bit '1' set if it is pointing to the page we want.
|
|
* but if the writer is in the process of moving it
|
|
* than it will be '2' or already moved '0'.
|
|
*/
|
|
|
|
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
|
|
|
|
/*
|
|
* If we did not convert it, then we must try again.
|
|
*/
|
|
if (!ret)
|
|
goto spin;
|
|
|
|
/*
|
|
* Yeah! We succeeded in replacing the page.
|
|
*
|
|
* Now make the new head point back to the reader page.
|
|
*/
|
|
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
|
|
rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
|
|
|
|
/* Finally update the reader page to the new head */
|
|
cpu_buffer->reader_page = reader;
|
|
rb_reset_reader_page(cpu_buffer);
|
|
|
|
if (overwrite != cpu_buffer->last_overrun) {
|
|
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
|
|
cpu_buffer->last_overrun = overwrite;
|
|
}
|
|
|
|
goto again;
|
|
|
|
out:
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
local_irq_restore(flags);
|
|
|
|
return reader;
|
|
}
|
|
|
|
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *reader;
|
|
unsigned length;
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
|
|
/* This function should not be called when buffer is empty */
|
|
if (RB_WARN_ON(cpu_buffer, !reader))
|
|
return;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
|
|
cpu_buffer->read++;
|
|
|
|
rb_update_read_stamp(cpu_buffer, event);
|
|
|
|
length = rb_event_length(event);
|
|
cpu_buffer->reader_page->read += length;
|
|
}
|
|
|
|
static void rb_advance_iter(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned length;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
/*
|
|
* Check if we are at the end of the buffer.
|
|
*/
|
|
if (iter->head >= rb_page_size(iter->head_page)) {
|
|
/* discarded commits can make the page empty */
|
|
if (iter->head_page == cpu_buffer->commit_page)
|
|
return;
|
|
rb_inc_iter(iter);
|
|
return;
|
|
}
|
|
|
|
event = rb_iter_head_event(iter);
|
|
|
|
length = rb_event_length(event);
|
|
|
|
/*
|
|
* This should not be called to advance the header if we are
|
|
* at the tail of the buffer.
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
(iter->head_page == cpu_buffer->commit_page) &&
|
|
(iter->head + length > rb_commit_index(cpu_buffer))))
|
|
return;
|
|
|
|
rb_update_iter_read_stamp(iter, event);
|
|
|
|
iter->head += length;
|
|
|
|
/* check for end of page padding */
|
|
if ((iter->head >= rb_page_size(iter->head_page)) &&
|
|
(iter->head_page != cpu_buffer->commit_page))
|
|
rb_inc_iter(iter);
|
|
}
|
|
|
|
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return cpu_buffer->lost_events;
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *reader;
|
|
int nr_loops = 0;
|
|
|
|
again:
|
|
/*
|
|
* We repeat when a time extend is encountered.
|
|
* Since the time extend is always attached to a data event,
|
|
* we should never loop more than once.
|
|
* (We never hit the following condition more than twice).
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
|
|
return NULL;
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (!reader)
|
|
return NULL;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (rb_null_event(event))
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
/*
|
|
* Because the writer could be discarding every
|
|
* event it creates (which would probably be bad)
|
|
* if we were to go back to "again" then we may never
|
|
* catch up, and will trigger the warn on, or lock
|
|
* the box. Return the padding, and we will release
|
|
* the current locks, and try again.
|
|
*/
|
|
return event;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts) {
|
|
*ts = cpu_buffer->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
if (lost_events)
|
|
*lost_events = rb_lost_events(cpu_buffer);
|
|
return event;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_peek);
|
|
|
|
static struct ring_buffer_event *
|
|
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct ring_buffer *buffer;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int nr_loops = 0;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
buffer = cpu_buffer->buffer;
|
|
|
|
/*
|
|
* Check if someone performed a consuming read to
|
|
* the buffer. A consuming read invalidates the iterator
|
|
* and we need to reset the iterator in this case.
|
|
*/
|
|
if (unlikely(iter->cache_read != cpu_buffer->read ||
|
|
iter->cache_reader_page != cpu_buffer->reader_page))
|
|
rb_iter_reset(iter);
|
|
|
|
again:
|
|
if (ring_buffer_iter_empty(iter))
|
|
return NULL;
|
|
|
|
/*
|
|
* We repeat when a time extend is encountered.
|
|
* Since the time extend is always attached to a data event,
|
|
* we should never loop more than once.
|
|
* (We never hit the following condition more than twice).
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
|
|
return NULL;
|
|
|
|
if (rb_per_cpu_empty(cpu_buffer))
|
|
return NULL;
|
|
|
|
if (iter->head >= local_read(&iter->head_page->page->commit)) {
|
|
rb_inc_iter(iter);
|
|
goto again;
|
|
}
|
|
|
|
event = rb_iter_head_event(iter);
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (rb_null_event(event)) {
|
|
rb_inc_iter(iter);
|
|
goto again;
|
|
}
|
|
rb_advance_iter(iter);
|
|
return event;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts) {
|
|
*ts = iter->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
return event;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
|
|
|
|
static inline int rb_ok_to_lock(void)
|
|
{
|
|
/*
|
|
* If an NMI die dumps out the content of the ring buffer
|
|
* do not grab locks. We also permanently disable the ring
|
|
* buffer too. A one time deal is all you get from reading
|
|
* the ring buffer from an NMI.
|
|
*/
|
|
if (likely(!in_nmi()))
|
|
return 1;
|
|
|
|
tracing_off_permanent();
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_peek - peek at the next event to be read
|
|
* @buffer: The ring buffer to read
|
|
* @cpu: The cpu to peak at
|
|
* @ts: The timestamp counter of this event.
|
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
|
*
|
|
* This will return the event that will be read next, but does
|
|
* not consume the data.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
int dolock;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
dolock = rb_ok_to_lock();
|
|
again:
|
|
local_irq_save(flags);
|
|
if (dolock)
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
rb_advance_reader(cpu_buffer);
|
|
if (dolock)
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
local_irq_restore(flags);
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_iter_peek - peek at the next event to be read
|
|
* @iter: The ring buffer iterator
|
|
* @ts: The timestamp counter of this event.
|
|
*
|
|
* This will return the event that will be read next, but does
|
|
* not increment the iterator.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
|
|
again:
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
event = rb_iter_peek(iter, ts);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_consume - return an event and consume it
|
|
* @buffer: The ring buffer to get the next event from
|
|
* @cpu: the cpu to read the buffer from
|
|
* @ts: a variable to store the timestamp (may be NULL)
|
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
|
*
|
|
* Returns the next event in the ring buffer, and that event is consumed.
|
|
* Meaning, that sequential reads will keep returning a different event,
|
|
* and eventually empty the ring buffer if the producer is slower.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event = NULL;
|
|
unsigned long flags;
|
|
int dolock;
|
|
|
|
dolock = rb_ok_to_lock();
|
|
|
|
again:
|
|
/* might be called in atomic */
|
|
preempt_disable();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
if (dolock)
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
|
if (event) {
|
|
cpu_buffer->lost_events = 0;
|
|
rb_advance_reader(cpu_buffer);
|
|
}
|
|
|
|
if (dolock)
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
local_irq_restore(flags);
|
|
|
|
out:
|
|
preempt_enable();
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_consume);
|
|
|
|
/**
|
|
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
|
|
* @buffer: The ring buffer to read from
|
|
* @cpu: The cpu buffer to iterate over
|
|
*
|
|
* This performs the initial preparations necessary to iterate
|
|
* through the buffer. Memory is allocated, buffer recording
|
|
* is disabled, and the iterator pointer is returned to the caller.
|
|
*
|
|
* Disabling buffer recordng prevents the reading from being
|
|
* corrupted. This is not a consuming read, so a producer is not
|
|
* expected.
|
|
*
|
|
* After a sequence of ring_buffer_read_prepare calls, the user is
|
|
* expected to make at least one call to ring_buffer_read_prepare_sync.
|
|
* Afterwards, ring_buffer_read_start is invoked to get things going
|
|
* for real.
|
|
*
|
|
* This overall must be paired with ring_buffer_read_finish.
|
|
*/
|
|
struct ring_buffer_iter *
|
|
ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_iter *iter;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
|
|
if (!iter)
|
|
return NULL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
iter->cpu_buffer = cpu_buffer;
|
|
|
|
atomic_inc(&buffer->resize_disabled);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
|
|
return iter;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
|
|
|
|
/**
|
|
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
|
|
*
|
|
* All previously invoked ring_buffer_read_prepare calls to prepare
|
|
* iterators will be synchronized. Afterwards, read_buffer_read_start
|
|
* calls on those iterators are allowed.
|
|
*/
|
|
void
|
|
ring_buffer_read_prepare_sync(void)
|
|
{
|
|
synchronize_sched();
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
|
|
|
|
/**
|
|
* ring_buffer_read_start - start a non consuming read of the buffer
|
|
* @iter: The iterator returned by ring_buffer_read_prepare
|
|
*
|
|
* This finalizes the startup of an iteration through the buffer.
|
|
* The iterator comes from a call to ring_buffer_read_prepare and
|
|
* an intervening ring_buffer_read_prepare_sync must have been
|
|
* performed.
|
|
*
|
|
* Must be paired with ring_buffer_read_finish.
|
|
*/
|
|
void
|
|
ring_buffer_read_start(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
if (!iter)
|
|
return;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
rb_iter_reset(iter);
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
|
|
|
|
/**
|
|
* ring_buffer_read_finish - finish reading the iterator of the buffer
|
|
* @iter: The iterator retrieved by ring_buffer_start
|
|
*
|
|
* This re-enables the recording to the buffer, and frees the
|
|
* iterator.
|
|
*/
|
|
void
|
|
ring_buffer_read_finish(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* Ring buffer is disabled from recording, here's a good place
|
|
* to check the integrity of the ring buffer.
|
|
* Must prevent readers from trying to read, as the check
|
|
* clears the HEAD page and readers require it.
|
|
*/
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_check_pages(cpu_buffer);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
atomic_dec(&cpu_buffer->buffer->resize_disabled);
|
|
kfree(iter);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
|
|
|
|
/**
|
|
* ring_buffer_read - read the next item in the ring buffer by the iterator
|
|
* @iter: The ring buffer iterator
|
|
* @ts: The time stamp of the event read.
|
|
*
|
|
* This reads the next event in the ring buffer and increments the iterator.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
again:
|
|
event = rb_iter_peek(iter, ts);
|
|
if (!event)
|
|
goto out;
|
|
|
|
if (event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
rb_advance_iter(iter);
|
|
out:
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return event;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read);
|
|
|
|
/**
|
|
* ring_buffer_size - return the size of the ring buffer (in bytes)
|
|
* @buffer: The ring buffer.
|
|
*/
|
|
unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
/*
|
|
* Earlier, this method returned
|
|
* BUF_PAGE_SIZE * buffer->nr_pages
|
|
* Since the nr_pages field is now removed, we have converted this to
|
|
* return the per cpu buffer value.
|
|
*/
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_size);
|
|
|
|
static void
|
|
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
local_set(&cpu_buffer->head_page->write, 0);
|
|
local_set(&cpu_buffer->head_page->entries, 0);
|
|
local_set(&cpu_buffer->head_page->page->commit, 0);
|
|
|
|
cpu_buffer->head_page->read = 0;
|
|
|
|
cpu_buffer->tail_page = cpu_buffer->head_page;
|
|
cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
local_set(&cpu_buffer->reader_page->write, 0);
|
|
local_set(&cpu_buffer->reader_page->entries, 0);
|
|
local_set(&cpu_buffer->reader_page->page->commit, 0);
|
|
cpu_buffer->reader_page->read = 0;
|
|
|
|
local_set(&cpu_buffer->entries_bytes, 0);
|
|
local_set(&cpu_buffer->overrun, 0);
|
|
local_set(&cpu_buffer->commit_overrun, 0);
|
|
local_set(&cpu_buffer->dropped_events, 0);
|
|
local_set(&cpu_buffer->entries, 0);
|
|
local_set(&cpu_buffer->committing, 0);
|
|
local_set(&cpu_buffer->commits, 0);
|
|
cpu_buffer->read = 0;
|
|
cpu_buffer->read_bytes = 0;
|
|
|
|
cpu_buffer->write_stamp = 0;
|
|
cpu_buffer->read_stamp = 0;
|
|
|
|
cpu_buffer->lost_events = 0;
|
|
cpu_buffer->last_overrun = 0;
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
|
|
* @buffer: The ring buffer to reset a per cpu buffer of
|
|
* @cpu: The CPU buffer to be reset
|
|
*/
|
|
void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
unsigned long flags;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
atomic_inc(&buffer->resize_disabled);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
|
|
/* Make sure all commits have finished */
|
|
synchronize_sched();
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
|
|
goto out;
|
|
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
rb_reset_cpu(cpu_buffer);
|
|
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
|
|
out:
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
atomic_dec(&buffer->resize_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
|
|
|
|
/**
|
|
* ring_buffer_reset - reset a ring buffer
|
|
* @buffer: The ring buffer to reset all cpu buffers
|
|
*/
|
|
void ring_buffer_reset(struct ring_buffer *buffer)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_buffer_cpu(buffer, cpu)
|
|
ring_buffer_reset_cpu(buffer, cpu);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset);
|
|
|
|
/**
|
|
* rind_buffer_empty - is the ring buffer empty?
|
|
* @buffer: The ring buffer to test
|
|
*/
|
|
int ring_buffer_empty(struct ring_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
int dolock;
|
|
int cpu;
|
|
int ret;
|
|
|
|
dolock = rb_ok_to_lock();
|
|
|
|
/* yes this is racy, but if you don't like the race, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
if (dolock)
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
ret = rb_per_cpu_empty(cpu_buffer);
|
|
if (dolock)
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
local_irq_restore(flags);
|
|
|
|
if (!ret)
|
|
return 0;
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty);
|
|
|
|
/**
|
|
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
|
|
* @buffer: The ring buffer
|
|
* @cpu: The CPU buffer to test
|
|
*/
|
|
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
int dolock;
|
|
int ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 1;
|
|
|
|
dolock = rb_ok_to_lock();
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
if (dolock)
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
ret = rb_per_cpu_empty(cpu_buffer);
|
|
if (dolock)
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
local_irq_restore(flags);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
|
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
|
/**
|
|
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
|
|
* @buffer_a: One buffer to swap with
|
|
* @buffer_b: The other buffer to swap with
|
|
*
|
|
* This function is useful for tracers that want to take a "snapshot"
|
|
* of a CPU buffer and has another back up buffer lying around.
|
|
* it is expected that the tracer handles the cpu buffer not being
|
|
* used at the moment.
|
|
*/
|
|
int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
|
|
struct ring_buffer *buffer_b, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer_a;
|
|
struct ring_buffer_per_cpu *cpu_buffer_b;
|
|
int ret = -EINVAL;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
|
|
!cpumask_test_cpu(cpu, buffer_b->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer_a = buffer_a->buffers[cpu];
|
|
cpu_buffer_b = buffer_b->buffers[cpu];
|
|
|
|
/* At least make sure the two buffers are somewhat the same */
|
|
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
|
|
goto out;
|
|
|
|
ret = -EAGAIN;
|
|
|
|
if (ring_buffer_flags != RB_BUFFERS_ON)
|
|
goto out;
|
|
|
|
if (atomic_read(&buffer_a->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&buffer_b->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&cpu_buffer_a->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&cpu_buffer_b->record_disabled))
|
|
goto out;
|
|
|
|
/*
|
|
* We can't do a synchronize_sched here because this
|
|
* function can be called in atomic context.
|
|
* Normally this will be called from the same CPU as cpu.
|
|
* If not it's up to the caller to protect this.
|
|
*/
|
|
atomic_inc(&cpu_buffer_a->record_disabled);
|
|
atomic_inc(&cpu_buffer_b->record_disabled);
|
|
|
|
ret = -EBUSY;
|
|
if (local_read(&cpu_buffer_a->committing))
|
|
goto out_dec;
|
|
if (local_read(&cpu_buffer_b->committing))
|
|
goto out_dec;
|
|
|
|
buffer_a->buffers[cpu] = cpu_buffer_b;
|
|
buffer_b->buffers[cpu] = cpu_buffer_a;
|
|
|
|
cpu_buffer_b->buffer = buffer_a;
|
|
cpu_buffer_a->buffer = buffer_b;
|
|
|
|
ret = 0;
|
|
|
|
out_dec:
|
|
atomic_dec(&cpu_buffer_a->record_disabled);
|
|
atomic_dec(&cpu_buffer_b->record_disabled);
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
|
|
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
|
|
|
|
/**
|
|
* ring_buffer_alloc_read_page - allocate a page to read from buffer
|
|
* @buffer: the buffer to allocate for.
|
|
* @cpu: the cpu buffer to allocate.
|
|
*
|
|
* This function is used in conjunction with ring_buffer_read_page.
|
|
* When reading a full page from the ring buffer, these functions
|
|
* can be used to speed up the process. The calling function should
|
|
* allocate a few pages first with this function. Then when it
|
|
* needs to get pages from the ring buffer, it passes the result
|
|
* of this function into ring_buffer_read_page, which will swap
|
|
* the page that was allocated, with the read page of the buffer.
|
|
*
|
|
* Returns:
|
|
* The page allocated, or NULL on error.
|
|
*/
|
|
void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct buffer_data_page *bpage;
|
|
struct page *page;
|
|
|
|
page = alloc_pages_node(cpu_to_node(cpu),
|
|
GFP_KERNEL | __GFP_NORETRY, 0);
|
|
if (!page)
|
|
return NULL;
|
|
|
|
bpage = page_address(page);
|
|
|
|
rb_init_page(bpage);
|
|
|
|
return bpage;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
|
|
|
|
/**
|
|
* ring_buffer_free_read_page - free an allocated read page
|
|
* @buffer: the buffer the page was allocate for
|
|
* @data: the page to free
|
|
*
|
|
* Free a page allocated from ring_buffer_alloc_read_page.
|
|
*/
|
|
void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
|
|
{
|
|
free_page((unsigned long)data);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
|
|
|
|
/**
|
|
* ring_buffer_read_page - extract a page from the ring buffer
|
|
* @buffer: buffer to extract from
|
|
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
|
|
* @len: amount to extract
|
|
* @cpu: the cpu of the buffer to extract
|
|
* @full: should the extraction only happen when the page is full.
|
|
*
|
|
* This function will pull out a page from the ring buffer and consume it.
|
|
* @data_page must be the address of the variable that was returned
|
|
* from ring_buffer_alloc_read_page. This is because the page might be used
|
|
* to swap with a page in the ring buffer.
|
|
*
|
|
* for example:
|
|
* rpage = ring_buffer_alloc_read_page(buffer, cpu);
|
|
* if (!rpage)
|
|
* return error;
|
|
* ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
|
|
* if (ret >= 0)
|
|
* process_page(rpage, ret);
|
|
*
|
|
* When @full is set, the function will not return true unless
|
|
* the writer is off the reader page.
|
|
*
|
|
* Note: it is up to the calling functions to handle sleeps and wakeups.
|
|
* The ring buffer can be used anywhere in the kernel and can not
|
|
* blindly call wake_up. The layer that uses the ring buffer must be
|
|
* responsible for that.
|
|
*
|
|
* Returns:
|
|
* >=0 if data has been transferred, returns the offset of consumed data.
|
|
* <0 if no data has been transferred.
|
|
*/
|
|
int ring_buffer_read_page(struct ring_buffer *buffer,
|
|
void **data_page, size_t len, int cpu, int full)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
struct ring_buffer_event *event;
|
|
struct buffer_data_page *bpage;
|
|
struct buffer_page *reader;
|
|
unsigned long missed_events;
|
|
unsigned long flags;
|
|
unsigned int commit;
|
|
unsigned int read;
|
|
u64 save_timestamp;
|
|
int ret = -1;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
/*
|
|
* If len is not big enough to hold the page header, then
|
|
* we can not copy anything.
|
|
*/
|
|
if (len <= BUF_PAGE_HDR_SIZE)
|
|
goto out;
|
|
|
|
len -= BUF_PAGE_HDR_SIZE;
|
|
|
|
if (!data_page)
|
|
goto out;
|
|
|
|
bpage = *data_page;
|
|
if (!bpage)
|
|
goto out;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (!reader)
|
|
goto out_unlock;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
read = reader->read;
|
|
commit = rb_page_commit(reader);
|
|
|
|
/* Check if any events were dropped */
|
|
missed_events = cpu_buffer->lost_events;
|
|
|
|
/*
|
|
* If this page has been partially read or
|
|
* if len is not big enough to read the rest of the page or
|
|
* a writer is still on the page, then
|
|
* we must copy the data from the page to the buffer.
|
|
* Otherwise, we can simply swap the page with the one passed in.
|
|
*/
|
|
if (read || (len < (commit - read)) ||
|
|
cpu_buffer->reader_page == cpu_buffer->commit_page) {
|
|
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
|
|
unsigned int rpos = read;
|
|
unsigned int pos = 0;
|
|
unsigned int size;
|
|
|
|
if (full)
|
|
goto out_unlock;
|
|
|
|
if (len > (commit - read))
|
|
len = (commit - read);
|
|
|
|
/* Always keep the time extend and data together */
|
|
size = rb_event_ts_length(event);
|
|
|
|
if (len < size)
|
|
goto out_unlock;
|
|
|
|
/* save the current timestamp, since the user will need it */
|
|
save_timestamp = cpu_buffer->read_stamp;
|
|
|
|
/* Need to copy one event at a time */
|
|
do {
|
|
/* We need the size of one event, because
|
|
* rb_advance_reader only advances by one event,
|
|
* whereas rb_event_ts_length may include the size of
|
|
* one or two events.
|
|
* We have already ensured there's enough space if this
|
|
* is a time extend. */
|
|
size = rb_event_length(event);
|
|
memcpy(bpage->data + pos, rpage->data + rpos, size);
|
|
|
|
len -= size;
|
|
|
|
rb_advance_reader(cpu_buffer);
|
|
rpos = reader->read;
|
|
pos += size;
|
|
|
|
if (rpos >= commit)
|
|
break;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
/* Always keep the time extend and data together */
|
|
size = rb_event_ts_length(event);
|
|
} while (len >= size);
|
|
|
|
/* update bpage */
|
|
local_set(&bpage->commit, pos);
|
|
bpage->time_stamp = save_timestamp;
|
|
|
|
/* we copied everything to the beginning */
|
|
read = 0;
|
|
} else {
|
|
/* update the entry counter */
|
|
cpu_buffer->read += rb_page_entries(reader);
|
|
cpu_buffer->read_bytes += BUF_PAGE_SIZE;
|
|
|
|
/* swap the pages */
|
|
rb_init_page(bpage);
|
|
bpage = reader->page;
|
|
reader->page = *data_page;
|
|
local_set(&reader->write, 0);
|
|
local_set(&reader->entries, 0);
|
|
reader->read = 0;
|
|
*data_page = bpage;
|
|
|
|
/*
|
|
* Use the real_end for the data size,
|
|
* This gives us a chance to store the lost events
|
|
* on the page.
|
|
*/
|
|
if (reader->real_end)
|
|
local_set(&bpage->commit, reader->real_end);
|
|
}
|
|
ret = read;
|
|
|
|
cpu_buffer->lost_events = 0;
|
|
|
|
commit = local_read(&bpage->commit);
|
|
/*
|
|
* Set a flag in the commit field if we lost events
|
|
*/
|
|
if (missed_events) {
|
|
/* If there is room at the end of the page to save the
|
|
* missed events, then record it there.
|
|
*/
|
|
if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
|
|
memcpy(&bpage->data[commit], &missed_events,
|
|
sizeof(missed_events));
|
|
local_add(RB_MISSED_STORED, &bpage->commit);
|
|
commit += sizeof(missed_events);
|
|
}
|
|
local_add(RB_MISSED_EVENTS, &bpage->commit);
|
|
}
|
|
|
|
/*
|
|
* This page may be off to user land. Zero it out here.
|
|
*/
|
|
if (commit < BUF_PAGE_SIZE)
|
|
memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
|
|
|
|
out_unlock:
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static int rb_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
struct ring_buffer *buffer =
|
|
container_of(self, struct ring_buffer, cpu_notify);
|
|
long cpu = (long)hcpu;
|
|
int cpu_i, nr_pages_same;
|
|
unsigned int nr_pages;
|
|
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
if (cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NOTIFY_OK;
|
|
|
|
nr_pages = 0;
|
|
nr_pages_same = 1;
|
|
/* check if all cpu sizes are same */
|
|
for_each_buffer_cpu(buffer, cpu_i) {
|
|
/* fill in the size from first enabled cpu */
|
|
if (nr_pages == 0)
|
|
nr_pages = buffer->buffers[cpu_i]->nr_pages;
|
|
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
|
|
nr_pages_same = 0;
|
|
break;
|
|
}
|
|
}
|
|
/* allocate minimum pages, user can later expand it */
|
|
if (!nr_pages_same)
|
|
nr_pages = 2;
|
|
buffer->buffers[cpu] =
|
|
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
|
if (!buffer->buffers[cpu]) {
|
|
WARN(1, "failed to allocate ring buffer on CPU %ld\n",
|
|
cpu);
|
|
return NOTIFY_OK;
|
|
}
|
|
smp_wmb();
|
|
cpumask_set_cpu(cpu, buffer->cpumask);
|
|
break;
|
|
case CPU_DOWN_PREPARE:
|
|
case CPU_DOWN_PREPARE_FROZEN:
|
|
/*
|
|
* Do nothing.
|
|
* If we were to free the buffer, then the user would
|
|
* lose any trace that was in the buffer.
|
|
*/
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
|
|
/*
|
|
* This is a basic integrity check of the ring buffer.
|
|
* Late in the boot cycle this test will run when configured in.
|
|
* It will kick off a thread per CPU that will go into a loop
|
|
* writing to the per cpu ring buffer various sizes of data.
|
|
* Some of the data will be large items, some small.
|
|
*
|
|
* Another thread is created that goes into a spin, sending out
|
|
* IPIs to the other CPUs to also write into the ring buffer.
|
|
* this is to test the nesting ability of the buffer.
|
|
*
|
|
* Basic stats are recorded and reported. If something in the
|
|
* ring buffer should happen that's not expected, a big warning
|
|
* is displayed and all ring buffers are disabled.
|
|
*/
|
|
static struct task_struct *rb_threads[NR_CPUS] __initdata;
|
|
|
|
struct rb_test_data {
|
|
struct ring_buffer *buffer;
|
|
unsigned long events;
|
|
unsigned long bytes_written;
|
|
unsigned long bytes_alloc;
|
|
unsigned long bytes_dropped;
|
|
unsigned long events_nested;
|
|
unsigned long bytes_written_nested;
|
|
unsigned long bytes_alloc_nested;
|
|
unsigned long bytes_dropped_nested;
|
|
int min_size_nested;
|
|
int max_size_nested;
|
|
int max_size;
|
|
int min_size;
|
|
int cpu;
|
|
int cnt;
|
|
};
|
|
|
|
static struct rb_test_data rb_data[NR_CPUS] __initdata;
|
|
|
|
/* 1 meg per cpu */
|
|
#define RB_TEST_BUFFER_SIZE 1048576
|
|
|
|
static char rb_string[] __initdata =
|
|
"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
|
|
"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
|
|
"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
|
|
|
|
static bool rb_test_started __initdata;
|
|
|
|
struct rb_item {
|
|
int size;
|
|
char str[];
|
|
};
|
|
|
|
static __init int rb_write_something(struct rb_test_data *data, bool nested)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct rb_item *item;
|
|
bool started;
|
|
int event_len;
|
|
int size;
|
|
int len;
|
|
int cnt;
|
|
|
|
/* Have nested writes different that what is written */
|
|
cnt = data->cnt + (nested ? 27 : 0);
|
|
|
|
/* Multiply cnt by ~e, to make some unique increment */
|
|
size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
|
|
|
|
len = size + sizeof(struct rb_item);
|
|
|
|
started = rb_test_started;
|
|
/* read rb_test_started before checking buffer enabled */
|
|
smp_rmb();
|
|
|
|
event = ring_buffer_lock_reserve(data->buffer, len);
|
|
if (!event) {
|
|
/* Ignore dropped events before test starts. */
|
|
if (started) {
|
|
if (nested)
|
|
data->bytes_dropped += len;
|
|
else
|
|
data->bytes_dropped_nested += len;
|
|
}
|
|
return len;
|
|
}
|
|
|
|
event_len = ring_buffer_event_length(event);
|
|
|
|
if (RB_WARN_ON(data->buffer, event_len < len))
|
|
goto out;
|
|
|
|
item = ring_buffer_event_data(event);
|
|
item->size = size;
|
|
memcpy(item->str, rb_string, size);
|
|
|
|
if (nested) {
|
|
data->bytes_alloc_nested += event_len;
|
|
data->bytes_written_nested += len;
|
|
data->events_nested++;
|
|
if (!data->min_size_nested || len < data->min_size_nested)
|
|
data->min_size_nested = len;
|
|
if (len > data->max_size_nested)
|
|
data->max_size_nested = len;
|
|
} else {
|
|
data->bytes_alloc += event_len;
|
|
data->bytes_written += len;
|
|
data->events++;
|
|
if (!data->min_size || len < data->min_size)
|
|
data->max_size = len;
|
|
if (len > data->max_size)
|
|
data->max_size = len;
|
|
}
|
|
|
|
out:
|
|
ring_buffer_unlock_commit(data->buffer, event);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init int rb_test(void *arg)
|
|
{
|
|
struct rb_test_data *data = arg;
|
|
|
|
while (!kthread_should_stop()) {
|
|
rb_write_something(data, false);
|
|
data->cnt++;
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
/* Now sleep between a min of 100-300us and a max of 1ms */
|
|
usleep_range(((data->cnt % 3) + 1) * 100, 1000);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init void rb_ipi(void *ignore)
|
|
{
|
|
struct rb_test_data *data;
|
|
int cpu = smp_processor_id();
|
|
|
|
data = &rb_data[cpu];
|
|
rb_write_something(data, true);
|
|
}
|
|
|
|
static __init int rb_hammer_test(void *arg)
|
|
{
|
|
while (!kthread_should_stop()) {
|
|
|
|
/* Send an IPI to all cpus to write data! */
|
|
smp_call_function(rb_ipi, NULL, 1);
|
|
/* No sleep, but for non preempt, let others run */
|
|
schedule();
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init int test_ringbuffer(void)
|
|
{
|
|
struct task_struct *rb_hammer;
|
|
struct ring_buffer *buffer;
|
|
int cpu;
|
|
int ret = 0;
|
|
|
|
pr_info("Running ring buffer tests...\n");
|
|
|
|
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
|
|
if (WARN_ON(!buffer))
|
|
return 0;
|
|
|
|
/* Disable buffer so that threads can't write to it yet */
|
|
ring_buffer_record_off(buffer);
|
|
|
|
for_each_online_cpu(cpu) {
|
|
rb_data[cpu].buffer = buffer;
|
|
rb_data[cpu].cpu = cpu;
|
|
rb_data[cpu].cnt = cpu;
|
|
rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
|
|
"rbtester/%d", cpu);
|
|
if (WARN_ON(!rb_threads[cpu])) {
|
|
pr_cont("FAILED\n");
|
|
ret = -1;
|
|
goto out_free;
|
|
}
|
|
|
|
kthread_bind(rb_threads[cpu], cpu);
|
|
wake_up_process(rb_threads[cpu]);
|
|
}
|
|
|
|
/* Now create the rb hammer! */
|
|
rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
|
|
if (WARN_ON(!rb_hammer)) {
|
|
pr_cont("FAILED\n");
|
|
ret = -1;
|
|
goto out_free;
|
|
}
|
|
|
|
ring_buffer_record_on(buffer);
|
|
/*
|
|
* Show buffer is enabled before setting rb_test_started.
|
|
* Yes there's a small race window where events could be
|
|
* dropped and the thread wont catch it. But when a ring
|
|
* buffer gets enabled, there will always be some kind of
|
|
* delay before other CPUs see it. Thus, we don't care about
|
|
* those dropped events. We care about events dropped after
|
|
* the threads see that the buffer is active.
|
|
*/
|
|
smp_wmb();
|
|
rb_test_started = true;
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
/* Just run for 10 seconds */;
|
|
schedule_timeout(10 * HZ);
|
|
|
|
kthread_stop(rb_hammer);
|
|
|
|
out_free:
|
|
for_each_online_cpu(cpu) {
|
|
if (!rb_threads[cpu])
|
|
break;
|
|
kthread_stop(rb_threads[cpu]);
|
|
}
|
|
if (ret) {
|
|
ring_buffer_free(buffer);
|
|
return ret;
|
|
}
|
|
|
|
/* Report! */
|
|
pr_info("finished\n");
|
|
for_each_online_cpu(cpu) {
|
|
struct ring_buffer_event *event;
|
|
struct rb_test_data *data = &rb_data[cpu];
|
|
struct rb_item *item;
|
|
unsigned long total_events;
|
|
unsigned long total_dropped;
|
|
unsigned long total_written;
|
|
unsigned long total_alloc;
|
|
unsigned long total_read = 0;
|
|
unsigned long total_size = 0;
|
|
unsigned long total_len = 0;
|
|
unsigned long total_lost = 0;
|
|
unsigned long lost;
|
|
int big_event_size;
|
|
int small_event_size;
|
|
|
|
ret = -1;
|
|
|
|
total_events = data->events + data->events_nested;
|
|
total_written = data->bytes_written + data->bytes_written_nested;
|
|
total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
|
|
total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
|
|
|
|
big_event_size = data->max_size + data->max_size_nested;
|
|
small_event_size = data->min_size + data->min_size_nested;
|
|
|
|
pr_info("CPU %d:\n", cpu);
|
|
pr_info(" events: %ld\n", total_events);
|
|
pr_info(" dropped bytes: %ld\n", total_dropped);
|
|
pr_info(" alloced bytes: %ld\n", total_alloc);
|
|
pr_info(" written bytes: %ld\n", total_written);
|
|
pr_info(" biggest event: %d\n", big_event_size);
|
|
pr_info(" smallest event: %d\n", small_event_size);
|
|
|
|
if (RB_WARN_ON(buffer, total_dropped))
|
|
break;
|
|
|
|
ret = 0;
|
|
|
|
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
|
|
total_lost += lost;
|
|
item = ring_buffer_event_data(event);
|
|
total_len += ring_buffer_event_length(event);
|
|
total_size += item->size + sizeof(struct rb_item);
|
|
if (memcmp(&item->str[0], rb_string, item->size) != 0) {
|
|
pr_info("FAILED!\n");
|
|
pr_info("buffer had: %.*s\n", item->size, item->str);
|
|
pr_info("expected: %.*s\n", item->size, rb_string);
|
|
RB_WARN_ON(buffer, 1);
|
|
ret = -1;
|
|
break;
|
|
}
|
|
total_read++;
|
|
}
|
|
if (ret)
|
|
break;
|
|
|
|
ret = -1;
|
|
|
|
pr_info(" read events: %ld\n", total_read);
|
|
pr_info(" lost events: %ld\n", total_lost);
|
|
pr_info(" total events: %ld\n", total_lost + total_read);
|
|
pr_info(" recorded len bytes: %ld\n", total_len);
|
|
pr_info(" recorded size bytes: %ld\n", total_size);
|
|
if (total_lost)
|
|
pr_info(" With dropped events, record len and size may not match\n"
|
|
" alloced and written from above\n");
|
|
if (!total_lost) {
|
|
if (RB_WARN_ON(buffer, total_len != total_alloc ||
|
|
total_size != total_written))
|
|
break;
|
|
}
|
|
if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
|
|
break;
|
|
|
|
ret = 0;
|
|
}
|
|
if (!ret)
|
|
pr_info("Ring buffer PASSED!\n");
|
|
|
|
ring_buffer_free(buffer);
|
|
return 0;
|
|
}
|
|
|
|
late_initcall(test_ringbuffer);
|
|
#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
|