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1// SPDX-License-Identifier: GPL-2.02/*3 * NMI backtrace support4 *5 * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,6 * with the following header:7 *8 * HW NMI watchdog support9 *10 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.11 *12 * Arch specific calls to support NMI watchdog13 *14 * Bits copied from original nmi.c file15 */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_backtrace24/* 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 the32 * backtrace_mask. Architectures that call nmi_cpu_backtrace()33 * directly from their raise() functions may rely on the mask34 * they are passed being updated as a side effect of this call.35 */36void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,37 int exclude_cpu,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 progress45 * (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_cpu != -1)53 cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask));54 55 /*56 * Don't try to send an NMI to this cpu; it may work on some57 * architectures, but on others it may not, and we'll get58 * 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 nmi_backtrace_stall_snap(to_cpumask(backtrace_mask));68 raise(to_cpumask(backtrace_mask));69 }70 71 /* Wait for up to 10 seconds for all CPUs to do the backtrace */72 for (i = 0; i < 10 * 1000; i++) {73 if (cpumask_empty(to_cpumask(backtrace_mask)))74 break;75 mdelay(1);76 touch_softlockup_watchdog();77 }78 nmi_backtrace_stall_check(to_cpumask(backtrace_mask));79 80 /*81 * Force flush any remote buffers that might be stuck in IRQ context82 * and therefore could not run their irq_work.83 */84 printk_trigger_flush();85 86 clear_bit_unlock(0, &backtrace_flag);87 put_cpu();88}89 90// Dump stacks even for idle CPUs.91static bool backtrace_idle;92module_param(backtrace_idle, bool, 0644);93 94bool nmi_cpu_backtrace(struct pt_regs *regs)95{96 int cpu = smp_processor_id();97 unsigned long flags;98 99 if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {100 /*101 * Allow nested NMI backtraces while serializing102 * against other CPUs.103 */104 printk_cpu_sync_get_irqsave(flags);105 if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {106 pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",107 cpu, (void *)instruction_pointer(regs));108 } else {109 pr_warn("NMI backtrace for cpu %d\n", cpu);110 if (regs)111 show_regs(regs);112 else113 dump_stack();114 }115 printk_cpu_sync_put_irqrestore(flags);116 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));117 return true;118 }119 120 return false;121}122NOKPROBE_SYMBOL(nmi_cpu_backtrace);123#endif124