linux/lib/nmi_backtrace.c
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   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. */
  23static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
  24
  25/* "in progress" flag of arch_trigger_cpumask_backtrace */
  26static 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 */
  34void 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
  86bool 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}
 107NOKPROBE_SYMBOL(nmi_cpu_backtrace);
 108#endif
 109