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// 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);
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