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![Peter Zijlstra](/assets/img/avatar_default.png)
Since only samples call perf_output_sample() its much saner (and more correct) to put the sample logic in there than in the perf_output_begin()/perf_output_end() pair. Saves a useless argument, reduces conditionals and shrinks struct perf_output_handle, win! Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/n/tip-2crpvsx3cqu67q3zqjbnlpsc@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
380 lines
7.8 KiB
C
380 lines
7.8 KiB
C
/*
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* Performance events ring-buffer code:
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*
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* Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
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* Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
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* Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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* Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
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*
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* For licensing details see kernel-base/COPYING
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*/
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#include <linux/perf_event.h>
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#include "internal.h"
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static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
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unsigned long offset, unsigned long head)
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{
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unsigned long mask;
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if (!rb->writable)
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return true;
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mask = perf_data_size(rb) - 1;
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offset = (offset - tail) & mask;
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head = (head - tail) & mask;
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if ((int)(head - offset) < 0)
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return false;
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return true;
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}
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static void perf_output_wakeup(struct perf_output_handle *handle)
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{
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atomic_set(&handle->rb->poll, POLL_IN);
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handle->event->pending_wakeup = 1;
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irq_work_queue(&handle->event->pending);
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}
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/*
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* We need to ensure a later event_id doesn't publish a head when a former
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* event isn't done writing. However since we need to deal with NMIs we
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* cannot fully serialize things.
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*
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* We only publish the head (and generate a wakeup) when the outer-most
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* event completes.
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*/
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static void perf_output_get_handle(struct perf_output_handle *handle)
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{
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struct ring_buffer *rb = handle->rb;
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preempt_disable();
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local_inc(&rb->nest);
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handle->wakeup = local_read(&rb->wakeup);
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}
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static void perf_output_put_handle(struct perf_output_handle *handle)
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{
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struct ring_buffer *rb = handle->rb;
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unsigned long head;
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again:
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head = local_read(&rb->head);
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/*
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* IRQ/NMI can happen here, which means we can miss a head update.
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*/
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if (!local_dec_and_test(&rb->nest))
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goto out;
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/*
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* Publish the known good head. Rely on the full barrier implied
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* by atomic_dec_and_test() order the rb->head read and this
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* write.
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*/
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rb->user_page->data_head = head;
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/*
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* Now check if we missed an update, rely on the (compiler)
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* barrier in atomic_dec_and_test() to re-read rb->head.
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*/
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if (unlikely(head != local_read(&rb->head))) {
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local_inc(&rb->nest);
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goto again;
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}
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if (handle->wakeup != local_read(&rb->wakeup))
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perf_output_wakeup(handle);
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out:
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preempt_enable();
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}
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int perf_output_begin(struct perf_output_handle *handle,
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struct perf_event *event, unsigned int size)
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{
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struct ring_buffer *rb;
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unsigned long tail, offset, head;
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int have_lost;
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struct perf_sample_data sample_data;
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struct {
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struct perf_event_header header;
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u64 id;
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u64 lost;
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} lost_event;
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rcu_read_lock();
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/*
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* For inherited events we send all the output towards the parent.
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*/
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if (event->parent)
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event = event->parent;
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rb = rcu_dereference(event->rb);
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if (!rb)
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goto out;
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handle->rb = rb;
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handle->event = event;
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if (!rb->nr_pages)
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goto out;
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have_lost = local_read(&rb->lost);
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if (have_lost) {
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lost_event.header.size = sizeof(lost_event);
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perf_event_header__init_id(&lost_event.header, &sample_data,
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event);
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size += lost_event.header.size;
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}
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perf_output_get_handle(handle);
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do {
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/*
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* Userspace could choose to issue a mb() before updating the
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* tail pointer. So that all reads will be completed before the
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* write is issued.
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*/
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tail = ACCESS_ONCE(rb->user_page->data_tail);
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smp_rmb();
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offset = head = local_read(&rb->head);
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head += size;
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if (unlikely(!perf_output_space(rb, tail, offset, head)))
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goto fail;
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} while (local_cmpxchg(&rb->head, offset, head) != offset);
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if (head - local_read(&rb->wakeup) > rb->watermark)
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local_add(rb->watermark, &rb->wakeup);
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handle->page = offset >> (PAGE_SHIFT + page_order(rb));
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handle->page &= rb->nr_pages - 1;
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handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
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handle->addr = rb->data_pages[handle->page];
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handle->addr += handle->size;
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handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
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if (have_lost) {
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lost_event.header.type = PERF_RECORD_LOST;
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lost_event.header.misc = 0;
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lost_event.id = event->id;
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lost_event.lost = local_xchg(&rb->lost, 0);
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perf_output_put(handle, lost_event);
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perf_event__output_id_sample(event, handle, &sample_data);
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}
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return 0;
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fail:
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local_inc(&rb->lost);
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perf_output_put_handle(handle);
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out:
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rcu_read_unlock();
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return -ENOSPC;
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}
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void perf_output_copy(struct perf_output_handle *handle,
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const void *buf, unsigned int len)
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{
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__output_copy(handle, buf, len);
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}
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void perf_output_end(struct perf_output_handle *handle)
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{
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perf_output_put_handle(handle);
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rcu_read_unlock();
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}
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static void
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ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
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{
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long max_size = perf_data_size(rb);
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if (watermark)
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rb->watermark = min(max_size, watermark);
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if (!rb->watermark)
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rb->watermark = max_size / 2;
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if (flags & RING_BUFFER_WRITABLE)
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rb->writable = 1;
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atomic_set(&rb->refcount, 1);
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}
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#ifndef CONFIG_PERF_USE_VMALLOC
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/*
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* Back perf_mmap() with regular GFP_KERNEL-0 pages.
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*/
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struct page *
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perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
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{
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if (pgoff > rb->nr_pages)
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return NULL;
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if (pgoff == 0)
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return virt_to_page(rb->user_page);
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return virt_to_page(rb->data_pages[pgoff - 1]);
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}
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static void *perf_mmap_alloc_page(int cpu)
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{
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struct page *page;
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int node;
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node = (cpu == -1) ? cpu : cpu_to_node(cpu);
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page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
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if (!page)
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return NULL;
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return page_address(page);
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}
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struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
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{
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struct ring_buffer *rb;
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unsigned long size;
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int i;
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size = sizeof(struct ring_buffer);
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size += nr_pages * sizeof(void *);
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rb = kzalloc(size, GFP_KERNEL);
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if (!rb)
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goto fail;
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rb->user_page = perf_mmap_alloc_page(cpu);
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if (!rb->user_page)
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goto fail_user_page;
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for (i = 0; i < nr_pages; i++) {
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rb->data_pages[i] = perf_mmap_alloc_page(cpu);
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if (!rb->data_pages[i])
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goto fail_data_pages;
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}
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rb->nr_pages = nr_pages;
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ring_buffer_init(rb, watermark, flags);
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return rb;
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fail_data_pages:
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for (i--; i >= 0; i--)
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free_page((unsigned long)rb->data_pages[i]);
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free_page((unsigned long)rb->user_page);
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fail_user_page:
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kfree(rb);
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fail:
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return NULL;
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}
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static void perf_mmap_free_page(unsigned long addr)
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{
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struct page *page = virt_to_page((void *)addr);
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page->mapping = NULL;
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__free_page(page);
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}
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void rb_free(struct ring_buffer *rb)
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{
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int i;
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perf_mmap_free_page((unsigned long)rb->user_page);
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for (i = 0; i < rb->nr_pages; i++)
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perf_mmap_free_page((unsigned long)rb->data_pages[i]);
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kfree(rb);
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}
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#else
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struct page *
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perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
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{
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if (pgoff > (1UL << page_order(rb)))
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return NULL;
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return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
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}
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static void perf_mmap_unmark_page(void *addr)
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{
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struct page *page = vmalloc_to_page(addr);
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page->mapping = NULL;
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}
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static void rb_free_work(struct work_struct *work)
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{
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struct ring_buffer *rb;
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void *base;
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int i, nr;
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rb = container_of(work, struct ring_buffer, work);
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nr = 1 << page_order(rb);
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base = rb->user_page;
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for (i = 0; i < nr + 1; i++)
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perf_mmap_unmark_page(base + (i * PAGE_SIZE));
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vfree(base);
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kfree(rb);
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}
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void rb_free(struct ring_buffer *rb)
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{
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schedule_work(&rb->work);
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}
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struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
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{
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struct ring_buffer *rb;
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unsigned long size;
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void *all_buf;
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size = sizeof(struct ring_buffer);
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size += sizeof(void *);
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rb = kzalloc(size, GFP_KERNEL);
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if (!rb)
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goto fail;
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INIT_WORK(&rb->work, rb_free_work);
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all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
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if (!all_buf)
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goto fail_all_buf;
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rb->user_page = all_buf;
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rb->data_pages[0] = all_buf + PAGE_SIZE;
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rb->page_order = ilog2(nr_pages);
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rb->nr_pages = 1;
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ring_buffer_init(rb, watermark, flags);
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return rb;
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fail_all_buf:
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kfree(rb);
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fail:
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return NULL;
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}
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#endif
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