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ring-buffer: Add recording of ring buffer recursion into recursed_functions

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Add a new config RING_BUFFER_RECORD_RECURSION that will place functions that
recurse from the ring buffer into the ftrace recused_functions file.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-11-02 14:43:10 -05:00
parent 7b68621f8d
commit 28575c61ea
2 changed files with 25 additions and 1 deletions
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14
kernel/trace/Kconfig
View file

@ -752,6 +752,20 @@ config FTRACE_RECORD_RECURSION_SIZE
This file can be reset, but the limit can not change in
size at runtime.
config RING_BUFFER_RECORD_RECURSION
bool "Record functions that recurse in the ring buffer"
depends on FTRACE_RECORD_RECURSION
# default y, because it is coupled with FTRACE_RECORD_RECURSION
default y
help
The ring buffer has its own internal recursion. Although when
recursion happens it wont cause harm because of the protection,
but it does cause an unwanted overhead. Enabling this option will
place where recursion was detected into the ftrace "recursed_functions"
file.
This will add more overhead to cases that have recursion.
config GCOV_PROFILE_FTRACE
bool "Enable GCOV profiling on ftrace subsystem"
depends on GCOV_KERNEL

12
kernel/trace/ring_buffer.c
View file

@ -4,6 +4,7 @@
*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/trace_recursion.h>
#include <linux/trace_events.h>
#include <linux/ring_buffer.h>
#include <linux/trace_clock.h>
@ -3006,6 +3007,13 @@ rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
irq_work_queue(&cpu_buffer->irq_work.work);
}
#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
# define do_ring_buffer_record_recursion() \
do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
#else
# define do_ring_buffer_record_recursion() do { } while (0)
#endif
/*
* The lock and unlock are done within a preempt disable section.
* The current_context per_cpu variable can only be modified
@ -3088,8 +3096,10 @@ trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
* been updated yet. In this case, use the TRANSITION bit.
*/
bit = RB_CTX_TRANSITION;
if (val & (1 << (bit + cpu_buffer->nest)))
if (val & (1 << (bit + cpu_buffer->nest))) {
do_ring_buffer_record_recursion();
return 1;
}
}
val |= (1 << (bit + cpu_buffer->nest));