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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. */ | |
23 | static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; | |
24 | ||
25 | /* "in progress" flag of arch_trigger_cpumask_backtrace */ | |
26 | static 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 | */ | |
34 | void 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 | ||
86 | bool 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 | } | |
107 | NOKPROBE_SYMBOL(nmi_cpu_backtrace); | |
108 | #endif |