linux/lib/dump_stack.c
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   1/*
   2 * Provide a default dump_stack() function for architectures
   3 * which don't implement their own.
   4 */
   5
   6#include <linux/kernel.h>
   7#include <linux/export.h>
   8#include <linux/sched.h>
   9#include <linux/smp.h>
  10#include <linux/atomic.h>
  11
  12static void __dump_stack(void)
  13{
  14        dump_stack_print_info(KERN_DEFAULT);
  15        show_stack(NULL, NULL);
  16}
  17
  18/**
  19 * dump_stack - dump the current task information and its stack trace
  20 *
  21 * Architectures can override this implementation by implementing its own.
  22 */
  23#ifdef CONFIG_SMP
  24static atomic_t dump_lock = ATOMIC_INIT(-1);
  25
  26void dump_stack(void)
  27{
  28        int was_locked;
  29        int old;
  30        int cpu;
  31
  32        /*
  33         * Permit this cpu to perform nested stack dumps while serialising
  34         * against other CPUs
  35         */
  36        preempt_disable();
  37
  38retry:
  39        cpu = smp_processor_id();
  40        old = atomic_cmpxchg(&dump_lock, -1, cpu);
  41        if (old == -1) {
  42                was_locked = 0;
  43        } else if (old == cpu) {
  44                was_locked = 1;
  45        } else {
  46                cpu_relax();
  47                goto retry;
  48        }
  49
  50        __dump_stack();
  51
  52        if (!was_locked)
  53                atomic_set(&dump_lock, -1);
  54
  55        preempt_enable();
  56}
  57#else
  58void dump_stack(void)
  59{
  60        __dump_stack();
  61}
  62#endif
  63EXPORT_SYMBOL(dump_stack);
  64
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