Commit 28575c61 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

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



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: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 7b68621f

kernel/trace/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -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

kernel/trace/ring_buffer.c

+11 −1
Original line number Diff line number Diff line
@@ -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
@@ -3088,9 +3096,11 @@ 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));

	cpu_buffer->current_context = val;