lib/dump_stack.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Provide a default dump_stack() function for architectures
   4  * which don't implement their own.
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/export.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/debug.h>
  11 #include <linux/smp.h>
  12 #include <linux/atomic.h>
  13
  14 static void __dump_stack(void)
  15 {
  16         dump_stack_print_info(KERN_DEFAULT);
  17         show_stack(NULL, NULL);
  18 }
  19
  20 /**
  21  * dump_stack - dump the current task information and its stack trace
  22  *
  23  * Architectures can override this implementation by implementing its own.
  24  */
  25 #ifdef CONFIG_SMP
  26 static atomic_t dump_lock = ATOMIC_INIT(-1);
  27
  28 asmlinkage __visible void dump_stack(void)
  29 {
  30         unsigned long flags;
  31         int was_locked;
  32         int old;
  33         int cpu;
  34
  35         /*
  36          * Permit this cpu to perform nested stack dumps while serialising
  37          * against other CPUs
  38          */
  39 retry:
  40         local_irq_save(flags);
  41         cpu = smp_processor_id();
  42         old = atomic_cmpxchg(&dump_lock, -1, cpu);
  43         if (old == -1) {
  44                 was_locked = 0;
  45         } else if (old == cpu) {
  46                 was_locked = 1;
  47         } else {
  48                 local_irq_restore(flags);
  49                 /*
  50                  * Wait for the lock to release before jumping to
  51                  * atomic_cmpxchg() in order to mitigate the thundering herd
  52                  * problem.
  53                  */
  54                 do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
  55                 goto retry;
  56         }
  57
  58         __dump_stack();
  59
  60         if (!was_locked)
  61                 atomic_set(&dump_lock, -1);
  62
  63         local_irq_restore(flags);
  64 }
  65 #else
  66 asmlinkage __visible void dump_stack(void)
  67 {
  68         __dump_stack();
  69 }
  70 #endif
  71 EXPORT_SYMBOL(dump_stack);