1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * NMI backtrace support
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
6*4882a593Smuzhiyun * with the following header:
7*4882a593Smuzhiyun *
8*4882a593Smuzhiyun * HW NMI watchdog support
9*4882a593Smuzhiyun *
10*4882a593Smuzhiyun * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
11*4882a593Smuzhiyun *
12*4882a593Smuzhiyun * Arch specific calls to support NMI watchdog
13*4882a593Smuzhiyun *
14*4882a593Smuzhiyun * Bits copied from original nmi.c file
15*4882a593Smuzhiyun */
16*4882a593Smuzhiyun #include <linux/cpumask.h>
17*4882a593Smuzhiyun #include <linux/delay.h>
18*4882a593Smuzhiyun #include <linux/kprobes.h>
19*4882a593Smuzhiyun #include <linux/nmi.h>
20*4882a593Smuzhiyun #include <linux/cpu.h>
21*4882a593Smuzhiyun #include <linux/sched/debug.h>
22*4882a593Smuzhiyun
23*4882a593Smuzhiyun #ifdef arch_trigger_cpumask_backtrace
24*4882a593Smuzhiyun /* For reliability, we're prepared to waste bits here. */
25*4882a593Smuzhiyun static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
26*4882a593Smuzhiyun
27*4882a593Smuzhiyun /* "in progress" flag of arch_trigger_cpumask_backtrace */
28*4882a593Smuzhiyun static unsigned long backtrace_flag;
29*4882a593Smuzhiyun
30*4882a593Smuzhiyun /*
31*4882a593Smuzhiyun * When raise() is called it will be passed a pointer to the
32*4882a593Smuzhiyun * backtrace_mask. Architectures that call nmi_cpu_backtrace()
33*4882a593Smuzhiyun * directly from their raise() functions may rely on the mask
34*4882a593Smuzhiyun * they are passed being updated as a side effect of this call.
35*4882a593Smuzhiyun */
nmi_trigger_cpumask_backtrace(const cpumask_t * mask,bool exclude_self,void (* raise)(cpumask_t * mask))36*4882a593Smuzhiyun void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
37*4882a593Smuzhiyun bool exclude_self,
38*4882a593Smuzhiyun void (*raise)(cpumask_t *mask))
39*4882a593Smuzhiyun {
40*4882a593Smuzhiyun int i, this_cpu = get_cpu();
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun if (test_and_set_bit(0, &backtrace_flag)) {
43*4882a593Smuzhiyun /*
44*4882a593Smuzhiyun * If there is already a trigger_all_cpu_backtrace() in progress
45*4882a593Smuzhiyun * (backtrace_flag == 1), don't output double cpu dump infos.
46*4882a593Smuzhiyun */
47*4882a593Smuzhiyun put_cpu();
48*4882a593Smuzhiyun return;
49*4882a593Smuzhiyun }
50*4882a593Smuzhiyun
51*4882a593Smuzhiyun cpumask_copy(to_cpumask(backtrace_mask), mask);
52*4882a593Smuzhiyun if (exclude_self)
53*4882a593Smuzhiyun cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
54*4882a593Smuzhiyun
55*4882a593Smuzhiyun /*
56*4882a593Smuzhiyun * Don't try to send an NMI to this cpu; it may work on some
57*4882a593Smuzhiyun * architectures, but on others it may not, and we'll get
58*4882a593Smuzhiyun * information at least as useful just by doing a dump_stack() here.
59*4882a593Smuzhiyun * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
60*4882a593Smuzhiyun */
61*4882a593Smuzhiyun if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
62*4882a593Smuzhiyun nmi_cpu_backtrace(NULL);
63*4882a593Smuzhiyun
64*4882a593Smuzhiyun if (!cpumask_empty(to_cpumask(backtrace_mask))) {
65*4882a593Smuzhiyun pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
66*4882a593Smuzhiyun this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
67*4882a593Smuzhiyun raise(to_cpumask(backtrace_mask));
68*4882a593Smuzhiyun }
69*4882a593Smuzhiyun
70*4882a593Smuzhiyun /* Wait for up to 10 seconds for all CPUs to do the backtrace */
71*4882a593Smuzhiyun for (i = 0; i < 10 * 1000; i++) {
72*4882a593Smuzhiyun if (cpumask_empty(to_cpumask(backtrace_mask)))
73*4882a593Smuzhiyun break;
74*4882a593Smuzhiyun mdelay(1);
75*4882a593Smuzhiyun touch_softlockup_watchdog();
76*4882a593Smuzhiyun }
77*4882a593Smuzhiyun
78*4882a593Smuzhiyun /*
79*4882a593Smuzhiyun * Force flush any remote buffers that might be stuck in IRQ context
80*4882a593Smuzhiyun * and therefore could not run their irq_work.
81*4882a593Smuzhiyun */
82*4882a593Smuzhiyun printk_safe_flush();
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun clear_bit_unlock(0, &backtrace_flag);
85*4882a593Smuzhiyun put_cpu();
86*4882a593Smuzhiyun }
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun // Dump stacks even for idle CPUs.
89*4882a593Smuzhiyun static bool backtrace_idle;
90*4882a593Smuzhiyun module_param(backtrace_idle, bool, 0644);
91*4882a593Smuzhiyun
nmi_cpu_backtrace(struct pt_regs * regs)92*4882a593Smuzhiyun bool nmi_cpu_backtrace(struct pt_regs *regs)
93*4882a593Smuzhiyun {
94*4882a593Smuzhiyun int cpu = smp_processor_id();
95*4882a593Smuzhiyun
96*4882a593Smuzhiyun if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
97*4882a593Smuzhiyun if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
98*4882a593Smuzhiyun pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
99*4882a593Smuzhiyun cpu, (void *)instruction_pointer(regs));
100*4882a593Smuzhiyun } else {
101*4882a593Smuzhiyun pr_warn("NMI backtrace for cpu %d\n", cpu);
102*4882a593Smuzhiyun if (regs)
103*4882a593Smuzhiyun show_regs(regs);
104*4882a593Smuzhiyun else
105*4882a593Smuzhiyun dump_stack();
106*4882a593Smuzhiyun }
107*4882a593Smuzhiyun cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
108*4882a593Smuzhiyun return true;
109*4882a593Smuzhiyun }
110*4882a593Smuzhiyun
111*4882a593Smuzhiyun return false;
112*4882a593Smuzhiyun }
113*4882a593Smuzhiyun NOKPROBE_SYMBOL(nmi_cpu_backtrace);
114*4882a593Smuzhiyun #endif
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