2 * NMI backtrace support
4 * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
5 * with the following header:
7 * HW NMI watchdog support
9 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
11 * Arch specific calls to support NMI watchdog
13 * Bits copied from original nmi.c file
15 #include <linux/cpumask.h>
16 #include <linux/delay.h>
17 #include <linux/kprobes.h>
18 #include <linux/nmi.h>
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;
24 /* "in progress" flag of arch_trigger_cpumask_backtrace */
25 static unsigned long backtrace_flag;
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.
33 void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
35 void (*raise)(cpumask_t *mask))
37 int i, this_cpu = get_cpu();
39 if (test_and_set_bit(0, &backtrace_flag)) {
41 * If there is already a trigger_all_cpu_backtrace() in progress
42 * (backtrace_flag == 1), don't output double cpu dump infos.
48 cpumask_copy(to_cpumask(backtrace_mask), mask);
50 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
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));
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)))
63 touch_softlockup_watchdog();
67 * Force flush any remote buffers that might be stuck in IRQ context
68 * and therefore could not run their irq_work.
72 clear_bit_unlock(0, &backtrace_flag);
76 bool nmi_cpu_backtrace(struct pt_regs *regs)
78 int cpu = smp_processor_id();
80 if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
81 pr_warn("NMI backtrace for cpu %d\n", cpu);
86 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
92 NOKPROBE_SYMBOL(nmi_cpu_backtrace);