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