LXR linux/lib/nmi_backtrace.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  NMI backtrace support
   4 *
   5 * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
   6 * with the following header:
   7 *
   8 *  HW NMI watchdog support
   9 *
  10 *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
  11 *
  12 *  Arch specific calls to support NMI watchdog
  13 *
  14 *  Bits copied from original nmi.c file
  15 */
  16#include <linux/cpumask.h>
  17#include <linux/delay.h>
  18#include <linux/kprobes.h>
  19#include <linux/nmi.h>
  20#include <linux/cpu.h>
  21#include <linux/sched/debug.h>
  22
  23#ifdef arch_trigger_cpumask_backtrace
  24/* For reliability, we're prepared to waste bits here. */
  25static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
  26
  27/* "in progress" flag of arch_trigger_cpumask_backtrace */
  28static unsigned long backtrace_flag;
  29
  30/*
  31 * When raise() is called it will be passed a pointer to the
  32 * backtrace_mask. Architectures that call nmi_cpu_backtrace()
  33 * directly from their raise() functions may rely on the mask
  34 * they are passed being updated as a side effect of this call.
  35 */
  36void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
  37                                   bool exclude_self,
  38                                   void (*raise)(cpumask_t *mask))
  39{
  40        int i, this_cpu = get_cpu();
  41
  42        if (test_and_set_bit(0, &backtrace_flag)) {
  43                /*
  44                 * If there is already a trigger_all_cpu_backtrace() in progress
  45                 * (backtrace_flag == 1), don't output double cpu dump infos.
  46                 */
  47                put_cpu();
  48                return;
  49        }
  50
  51        cpumask_copy(to_cpumask(backtrace_mask), mask);
  52        if (exclude_self)
  53                cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
  54
  55        /*
  56         * Don't try to send an NMI to this cpu; it may work on some
  57         * architectures, but on others it may not, and we'll get
  58         * information at least as useful just by doing a dump_stack() here.
  59         * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
  60         */
  61        if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
  62                nmi_cpu_backtrace(NULL);
  63
  64        if (!cpumask_empty(to_cpumask(backtrace_mask))) {
  65                pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
  66                        this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
  67                raise(to_cpumask(backtrace_mask));
  68        }
  69
  70        /* Wait for up to 10 seconds for all CPUs to do the backtrace */
  71        for (i = 0; i < 10 * 1000; i++) {
  72                if (cpumask_empty(to_cpumask(backtrace_mask)))
  73                        break;
  74                mdelay(1);
  75                touch_softlockup_watchdog();
  76        }
  77
  78        /*
  79         * Force flush any remote buffers that might be stuck in IRQ context
  80         * and therefore could not run their irq_work.
  81         */
  82        printk_safe_flush();
  83
  84        clear_bit_unlock(0, &backtrace_flag);
  85        put_cpu();
  86}
  87
  88// Dump stacks even for idle CPUs.
  89static bool backtrace_idle;
  90module_param(backtrace_idle, bool, 0644);
  91
  92bool nmi_cpu_backtrace(struct pt_regs *regs)
  93{
  94        int cpu = smp_processor_id();
  95
  96        if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
  97                if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
  98                        pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
  99                                cpu, (void *)instruction_pointer(regs));
 100                } else {
 101                        pr_warn("NMI backtrace for cpu %d\n", cpu);
 102                        if (regs)
 103                                show_regs(regs);
 104                        else
 105                                dump_stack();
 106                }
 107                cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 108                return true;
 109        }
 110
 111        return false;
 112}
 113NOKPROBE_SYMBOL(nmi_cpu_backtrace);
 114#endif
 115