projects/linux·blob uaccess-cleanups · refs

139 lines · 3.9 KiB

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/stringify.h>
20#include <linux/nmi.h>
21#include <linux/cpu.h>
22#include <linux/export.h>
23#include <linux/sched/debug.h>
24
25#ifdef arch_trigger_cpumask_backtrace
26/* For reliability, we're prepared to waste bits here. */
27static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
28
29/* "in progress" flag of arch_trigger_cpumask_backtrace */
30static unsigned long backtrace_flag;
31
32#define NMI_BT_TIMEOUT_SEC 10
33
34/*
35 * When raise() is called it will be passed a pointer to the
36 * backtrace_mask. Architectures that call nmi_cpu_backtrace()
37 * directly from their raise() functions may rely on the mask
38 * they are passed being updated as a side effect of this call.
39 */
40void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
41 int exclude_cpu,
42 void (*raise)(cpumask_t *mask))
43{
44 int i, this_cpu = get_cpu();
45
46 if (test_and_set_bit(0, &backtrace_flag)) {
47 /*
48 * If there is already a trigger_all_cpu_backtrace() in progress
49 * (backtrace_flag == 1), don't output double cpu dump infos.
50 */
51 put_cpu();
52 return;
53 }
54
55 cpumask_copy(to_cpumask(backtrace_mask), mask);
56 if (exclude_cpu != -1)
57 cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask));
58
59 /*
60 * Don't try to send an NMI to this cpu; it may work on some
61 * architectures, but on others it may not, and we'll get
62 * information at least as useful just by doing a dump_stack() here.
63 * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
64 */
65 if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
66 nmi_cpu_backtrace(NULL);
67
68 if (!cpumask_empty(to_cpumask(backtrace_mask))) {
69 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
70 this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
71 nmi_backtrace_stall_snap(to_cpumask(backtrace_mask));
72 raise(to_cpumask(backtrace_mask));
73 }
74
75 /* Wait for up to NMI_BT_TIMEOUT_SEC seconds for all CPUs to do the backtrace */
76 for (i = 0; i < NMI_BT_TIMEOUT_SEC * 1000; i++) {
77 if (cpumask_empty(to_cpumask(backtrace_mask)))
78 break;
79 mdelay(1);
80 touch_softlockup_watchdog();
81 }
82
83 if (!cpumask_empty(to_cpumask(backtrace_mask))) {
84 pr_warn("After " __stringify(NMI_BT_TIMEOUT_SEC) " seconds, these CPUS still haven't responded to the NMI: %*pbl\n",
85 cpumask_pr_args(to_cpumask(backtrace_mask)));
86
87 nmi_backtrace_stall_check(to_cpumask(backtrace_mask));
88 }
89
90 /*
91 * Force flush any remote buffers that might be stuck in IRQ context
92 * and therefore could not run their irq_work.
93 */
94 printk_trigger_flush();
95
96 clear_bit_unlock(0, &backtrace_flag);
97 put_cpu();
98}
99
100// Dump stacks even for idle CPUs.
101static bool backtrace_idle;
102module_param(backtrace_idle, bool, 0644);
103
104bool nmi_cpu_backtrace(struct pt_regs *regs)
105{
106 int cpu = smp_processor_id();
107 unsigned long flags;
108
109 if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
110 /*
111 * Allow nested NMI backtraces while serializing
112 * against other CPUs.
113 */
114 printk_cpu_sync_get_irqsave(flags);
115 if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
116 pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
117 cpu, (void *)instruction_pointer(regs));
118 } else {
119 pr_warn("NMI backtrace for cpu %d\n", cpu);
120 if (regs)
121 show_regs(regs);
122 else
123 dump_stack();
124 }
125 printk_cpu_sync_put_irqrestore(flags);
126 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
127 return true;
128 }
129
130 return false;
131}
132NOKPROBE_SYMBOL(nmi_cpu_backtrace);
133
134void cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
135{
136 arch_trigger_cpumask_backtrace(mask, exclude_cpu);
137}
138EXPORT_SYMBOL_GPL(cpumask_backtrace);
139#endif