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 #include <linux/sched/debug.h>
  21
  22 #ifdef arch_trigger_cpumask_backtrace
  23 /* For reliability, we're prepared to waste bits here. */
  24 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
  25
  26 /* "in progress" flag of arch_trigger_cpumask_backtrace */
  27 static unsigned long backtrace_flag;
  28
  29 /*
  30  * When raise() is called it will be passed a pointer to the
  31  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  32  * directly from their raise() functions may rely on the mask
  33  * they are passed being updated as a side effect of this call.
  34  */
  35 void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
  36                                    bool exclude_self,
  37                                    void (*raise)(cpumask_t *mask))
  38 {
  39         int i, this_cpu = get_cpu();
  40
  41         if (test_and_set_bit(0, &backtrace_flag)) {
  42                 /*
  43                  * If there is already a trigger_all_cpu_backtrace() in progress
  44                  * (backtrace_flag == 1), don't output double cpu dump infos.
  45                  */
  46                 put_cpu();
  47                 return;
  48         }
  49
  50         cpumask_copy(to_cpumask(backtrace_mask), mask);
  51         if (exclude_self)
  52                 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
  53
  54         /*
  55          * Don't try to send an NMI to this cpu; it may work on some
  56          * architectures, but on others it may not, and we'll get
  57          * information at least as useful just by doing a dump_stack() here.
  58          * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
  59          */
  60         if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
  61                 nmi_cpu_backtrace(NULL);
  62
  63         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
  64                 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
  65                         this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
  66                 raise(to_cpumask(backtrace_mask));
  67         }
  68
  69         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
  70         for (i = 0; i < 10 * 1000; i++) {
  71                 if (cpumask_empty(to_cpumask(backtrace_mask)))
  72                         break;
  73                 mdelay(1);
  74                 touch_softlockup_watchdog();
  75         }
  76
  77         /*
  78          * Force flush any remote buffers that might be stuck in IRQ context
  79          * and therefore could not run their irq_work.
  80          */
  81         printk_safe_flush();
  82
  83         clear_bit_unlock(0, &backtrace_flag);
  84         put_cpu();
  85 }
  86
  87 bool nmi_cpu_backtrace(struct pt_regs *regs)
  88 {
  89         static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
  90         int cpu = smp_processor_id();
  91
  92         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
  93                 arch_spin_lock(&lock);
  94                 if (regs && cpu_in_idle(instruction_pointer(regs))) {
  95                         pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
  96                                 cpu, instruction_pointer(regs));
  97                 } else {
  98                         pr_warn("NMI backtrace for cpu %d\n", cpu);
  99                         if (regs)
 100                                 show_regs(regs);
 101                         else
 102                                 dump_stack();
 103                 }
 104                 arch_spin_unlock(&lock);
 105                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 106                 return true;
 107         }
 108
 109         return false;
 110 }
 111 NOKPROBE_SYMBOL(nmi_cpu_backtrace);
 112 #endif