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         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
  53                 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
  54                         this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
  55                 raise(to_cpumask(backtrace_mask));
  56         }
  57
  58         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
  59         for (i = 0; i < 10 * 1000; i++) {
  60                 if (cpumask_empty(to_cpumask(backtrace_mask)))
  61                         break;
  62                 mdelay(1);
  63                 touch_softlockup_watchdog();
  64         }
  65
  66         /*
  67          * Force flush any remote buffers that might be stuck in IRQ context
  68          * and therefore could not run their irq_work.
  69          */
  70         printk_nmi_flush();
  71
  72         clear_bit_unlock(0, &backtrace_flag);
  73         put_cpu();
  74 }
  75
  76 bool nmi_cpu_backtrace(struct pt_regs *regs)
  77 {
  78         int cpu = smp_processor_id();
  79
  80         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
  81                 pr_warn("NMI backtrace for cpu %d\n", cpu);
  82                 if (regs)
  83                         show_regs(regs);
  84                 else
  85                         dump_stack();
  86                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
  87                 return true;
  88         }
  89
  90         return false;
  91 }
  92 NOKPROBE_SYMBOL(nmi_cpu_backtrace);
  93 #endif