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/nmi.h> |
20 | #include <linux/cpu.h> |
21 | #include <linux/sched/debug.h> |
22 | |
23 | #ifdef arch_trigger_cpumask_backtrace |
24 | /* For reliability, we're prepared to waste bits here. */ |
25 | static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; |
26 | |
27 | /* "in progress" flag of arch_trigger_cpumask_backtrace */ |
28 | static unsigned long backtrace_flag; |
29 | |
30 | /* |
31 | * When raise() is called it will be passed a pointer to the |
32 | * backtrace_mask. Architectures that call nmi_cpu_backtrace() |
33 | * directly from their raise() functions may rely on the mask |
34 | * they are passed being updated as a side effect of this call. |
35 | */ |
36 | void 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(nr: 0, addr: &backtrace_flag)) { |
43 | /* |
44 | * If there is already a trigger_all_cpu_backtrace() in progress |
45 | * (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), srcp: mask); |
52 | if (exclude_cpu != -1) |
53 | cpumask_clear_cpu(cpu: exclude_cpu, to_cpumask(backtrace_mask)); |
54 | |
55 | /* |
56 | * Don't try to send an NMI to this cpu; it may work on some |
57 | * architectures, but on others it may not, and we'll get |
58 | * 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(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 context |
82 | * and therefore could not run their irq_work. |
83 | */ |
84 | printk_trigger_flush(); |
85 | |
86 | clear_bit_unlock(nr: 0, addr: &backtrace_flag); |
87 | put_cpu(); |
88 | } |
89 | |
90 | // Dump stacks even for idle CPUs. |
91 | static bool backtrace_idle; |
92 | module_param(backtrace_idle, bool, 0644); |
93 | |
94 | bool 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 serializing |
102 | * against other CPUs. |
103 | */ |
104 | printk_cpu_sync_get_irqsave(flags); |
105 | if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(pc: 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 | else |
113 | 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 | } |
122 | NOKPROBE_SYMBOL(nmi_cpu_backtrace); |
123 | #endif |
124 | |