lib/dump_stack.c

   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
  12 static 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
  24 static atomic_t dump_lock = ATOMIC_INIT(-1);
  25
  26 asmlinkage __visible void dump_stack(void)
  27 {
  28         unsigned long flags;
  29         int was_locked;
  30         int old;
  31         int cpu;
  32
  33         /*
  34          * Permit this cpu to perform nested stack dumps while serialising
  35          * against other CPUs
  36          */
  37 retry:
  38         local_irq_save(flags);
  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                 local_irq_restore(flags);
  47                 /*
  48                  * Wait for the lock to release before jumping to
  49                  * atomic_cmpxchg() in order to mitigate the thundering herd
  50                  * problem.
  51                  */
  52                 do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
  53                 goto retry;
  54         }
  55
  56         __dump_stack();
  57
  58         if (!was_locked)
  59                 atomic_set(&dump_lock, -1);
  60
  61         local_irq_restore(flags);
  62 }
  63 #else
  64 asmlinkage __visible void dump_stack(void)
  65 {
  66         __dump_stack();
  67 }
  68 #endif
  69 EXPORT_SYMBOL(dump_stack);