lib/nmi_backtrace.c

   1 /*
   2  *  NMI backtrace support
   3  *
   4  * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
   5  * with the following header:
   6  *
   7  *  HW NMI watchdog support
   8  *
   9  *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
  10  *
  11  *  Arch specific calls to support NMI watchdog
  12  *
  13  *  Bits copied from original nmi.c file
  14  */
  15 #include <linux/cpumask.h>
  16 #include <linux/delay.h>
  17 #include <linux/kprobes.h>
  18 #include <linux/nmi.h>
  19
  20 #ifdef arch_trigger_all_cpu_backtrace
  21 /* For reliability, we're prepared to waste bits here. */
  22 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
  23
  24 /* "in progress" flag of arch_trigger_all_cpu_backtrace */
  25 static unsigned long backtrace_flag;
  26
  27 /*
  28  * When raise() is called it will be is passed a pointer to the
  29  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  30  * directly from their raise() functions may rely on the mask
  31  * they are passed being updated as a side effect of this call.
  32  */
  33 void nmi_trigger_all_cpu_backtrace(bool include_self,
  34                                    void (*raise)(cpumask_t *mask))
  35 {
  36         int i, this_cpu = get_cpu();
  37
  38         if (test_and_set_bit(0, &backtrace_flag)) {
  39                 /*
  40                  * If there is already a trigger_all_cpu_backtrace() in progress
  41                  * (backtrace_flag == 1), don't output double cpu dump infos.
  42                  */
  43                 put_cpu();
  44                 return;
  45         }
  46
  47         cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
  48         if (!include_self)
  49                 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
  50
  51         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
  52                 pr_info("Sending NMI to %s CPUs:\n",
  53                         (include_self ? "all" : "other"));
  54                 raise(to_cpumask(backtrace_mask));
  55         }
  56
  57         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
  58         for (i = 0; i < 10 * 1000; i++) {
  59                 if (cpumask_empty(to_cpumask(backtrace_mask)))
  60                         break;
  61                 mdelay(1);
  62                 touch_softlockup_watchdog();
  63         }
  64
  65         /*
  66          * Force flush any remote buffers that might be stuck in IRQ context
  67          * and therefore could not run their irq_work.
  68          */
  69         printk_nmi_flush();
  70
  71         clear_bit_unlock(0, &backtrace_flag);
  72         put_cpu();
  73 }
  74
  75 bool nmi_cpu_backtrace(struct pt_regs *regs)
  76 {
  77         int cpu = smp_processor_id();
  78
  79         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
  80                 pr_warn("NMI backtrace for cpu %d\n", cpu);
  81                 if (regs)
  82                         show_regs(regs);
  83                 else
  84                         dump_stack();
  85                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
  86                 return true;
  87         }
  88
  89         return false;
  90 }
  91 NOKPROBE_SYMBOL(nmi_cpu_backtrace);
  92 #endif