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 #include <linux/cpu.h>
  20
  21 #ifdef arch_trigger_cpumask_backtrace
  22 /* For reliability, we're prepared to waste bits here. */
  23 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
  24
  25 /* "in progress" flag of arch_trigger_cpumask_backtrace */
  26 static unsigned long backtrace_flag;
  27
  28 /*
  29  * When raise() is called it will be passed a pointer to the
  30  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  31  * directly from their raise() functions may rely on the mask
  32  * they are passed being updated as a side effect of this call.
  33  */
  34 void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
  35                                    bool exclude_self,
  36                                    void (*raise)(cpumask_t *mask))
  37 {
  38         int i, this_cpu = get_cpu();
  39
  40         if (test_and_set_bit(0, &backtrace_flag)) {
  41                 /*
  42                  * If there is already a trigger_all_cpu_backtrace() in progress
  43                  * (backtrace_flag == 1), don't output double cpu dump infos.
  44                  */
  45                 put_cpu();
  46                 return;
  47         }
  48
  49         cpumask_copy(to_cpumask(backtrace_mask), mask);
  50         if (exclude_self)
  51                 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
  52
  53         /*
  54          * Don't try to send an NMI to this cpu; it may work on some
  55          * architectures, but on others it may not, and we'll get
  56          * information at least as useful just by doing a dump_stack() here.
  57          * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
  58          */
  59         if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
  60                 nmi_cpu_backtrace(NULL);
  61
  62         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
  63                 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
  64                         this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
  65                 raise(to_cpumask(backtrace_mask));
  66         }
  67
  68         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
  69         for (i = 0; i < 10 * 1000; i++) {
  70                 if (cpumask_empty(to_cpumask(backtrace_mask)))
  71                         break;
  72                 mdelay(1);
  73                 touch_softlockup_watchdog();
  74         }
  75
  76         /*
  77          * Force flush any remote buffers that might be stuck in IRQ context
  78          * and therefore could not run their irq_work.
  79          */
  80         printk_nmi_flush();
  81
  82         clear_bit_unlock(0, &backtrace_flag);
  83         put_cpu();
  84 }
  85
  86 bool nmi_cpu_backtrace(struct pt_regs *regs)
  87 {
  88         int cpu = smp_processor_id();
  89
  90         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
  91                 if (regs && cpu_in_idle(instruction_pointer(regs))) {
  92                         pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
  93                                 cpu, instruction_pointer(regs));
  94                 } else {
  95                         pr_warn("NMI backtrace for cpu %d\n", cpu);
  96                         if (regs)
  97                                 show_regs(regs);
  98                         else
  99                                 dump_stack();
 100                 }
 101                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 102                 return true;
 103         }
 104
 105         return false;
 106 }
 107 NOKPROBE_SYMBOL(nmi_cpu_backtrace);
 108 #endif