mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-15 08:14:15 +08:00
e8b4d457b1
commit5cbf2fff3bupstream. In the current code, we use the atomic_cmpxchg() to serialize the output of the dump_stack(), but this implementation suffers the thundering herd problem. We have observed such kind of livelock on a Marvell cn96xx board(24 cpus) when heavily using the dump_stack() in a kprobe handler. Actually we can let the competitors to wait for the releasing of the lock before jumping to atomic_cmpxchg(). This will definitely mitigate the thundering herd problem. Thanks Linus for the suggestion. [akpm@linux-foundation.org: fix comment] Link: http://lkml.kernel.org/r/20191030031637.6025-1-haokexin@gmail.com Fixes:b58d977432("dump_stack: serialize the output from dump_stack()") Signed-off-by: Kevin Hao <haokexin@gmail.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
72 lines
1.4 KiB
C
72 lines
1.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Provide a default dump_stack() function for architectures
|
|
* which don't implement their own.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/sched/debug.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);
|
|
|
|
asmlinkage __visible void dump_stack(void)
|
|
{
|
|
unsigned long flags;
|
|
int was_locked;
|
|
int old;
|
|
int cpu;
|
|
|
|
/*
|
|
* Permit this cpu to perform nested stack dumps while serialising
|
|
* against other CPUs
|
|
*/
|
|
retry:
|
|
local_irq_save(flags);
|
|
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 {
|
|
local_irq_restore(flags);
|
|
/*
|
|
* Wait for the lock to release before jumping to
|
|
* atomic_cmpxchg() in order to mitigate the thundering herd
|
|
* problem.
|
|
*/
|
|
do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
|
|
goto retry;
|
|
}
|
|
|
|
__dump_stack();
|
|
|
|
if (!was_locked)
|
|
atomic_set(&dump_lock, -1);
|
|
|
|
local_irq_restore(flags);
|
|
}
|
|
#else
|
|
asmlinkage __visible void dump_stack(void)
|
|
{
|
|
__dump_stack();
|
|
}
|
|
#endif
|
|
EXPORT_SYMBOL(dump_stack);
|