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Commit b58d9774 authored by Alex Thorlton's avatar Alex Thorlton Committed by Linus Torvalds
Browse files

dump_stack: serialize the output from dump_stack() 



Add functionality to serialize the output from dump_stack() to avoid
mangling of the output when dump_stack is called simultaneously from
multiple cpus.

[akpm@linux-foundation.org: fix comment indenting, avoid inclusion of <asm/> files - use <linux/> where possiblem fix uniprocessor build (__dump_stack undefined), remove unneeded ifdef around smp.h inclusion]
Signed-off-by: default avatarAlex Thorlton <athorlton@sgi.com>
Reported-by: default avatarRuss Anderson <rja@sgi.com>
Reviewed-by: default avatarRobin Holt <holt@sgi.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f170168b

lib/dump_stack.c

+45 −2
Original line number Diff line number Diff line
@@ -6,15 +6,58 @@ 
#include <linux/kernel.h>

#include <linux/export.h>

#include <linux/sched.h>

#include <linux/smp.h>

#include <linux/atomic.h>



static void __dump_stack(void)

{

	dump_stack_print_info(KERN_DEFAULT);

	show_stack(NULL, NULL);

}



/**

 * dump_stack - dump the current task information and its stack trace

 *

 * Architectures can override this implementation by implementing its own.

 */

#ifdef CONFIG_SMP

static atomic_t dump_lock = ATOMIC_INIT(-1);



void dump_stack(void)

{

	dump_stack_print_info(KERN_DEFAULT);

	show_stack(NULL, NULL);

	int was_locked;

	int old;

	int cpu;



	/*

	 * Permit this cpu to perform nested stack dumps while serialising

	 * against other CPUs

	 */

	preempt_disable();



retry:

	cpu = smp_processor_id();

	old = atomic_cmpxchg(&dump_lock, -1, cpu);

	if (old == -1) {

		was_locked = 0;

	} else if (old == cpu) {

		was_locked = 1;

	} else {

		cpu_relax();

		goto retry;

	}



	__dump_stack();



	if (!was_locked)

		atomic_set(&dump_lock, -1);



	preempt_enable();

}

#else

void dump_stack(void)

{

	__dump_stack();

}

#endif

EXPORT_SYMBOL(dump_stack);