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