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1 // SPDX-License-Identifier: GPL-2.0
3 * NMI backtrace support
5 * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
6 * with the following header:
8 * HW NMI watchdog support
10 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
12 * Arch specific calls to support NMI watchdog
14 * Bits copied from original nmi.c file
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>
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
;
27 /* "in progress" flag of arch_trigger_cpumask_backtrace */
28 static unsigned long backtrace_flag
;
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.
36 void nmi_trigger_cpumask_backtrace(const cpumask_t
*mask
,
38 void (*raise
)(cpumask_t
*mask
))
40 int i
, this_cpu
= get_cpu();
42 if (test_and_set_bit(0, &backtrace_flag
)) {
44 * If there is already a trigger_all_cpu_backtrace() in progress
45 * (backtrace_flag == 1), don't output double cpu dump infos.
51 cpumask_copy(to_cpumask(backtrace_mask
), mask
);
53 cpumask_clear_cpu(this_cpu
, to_cpumask(backtrace_mask
));
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.
61 if (cpumask_test_cpu(this_cpu
, to_cpumask(backtrace_mask
)))
62 nmi_cpu_backtrace(NULL
);
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 raise(to_cpumask(backtrace_mask
));
70 /* Wait for up to 10 seconds for all CPUs to do the backtrace */
71 for (i
= 0; i
< 10 * 1000; i
++) {
72 if (cpumask_empty(to_cpumask(backtrace_mask
)))
75 touch_softlockup_watchdog();
78 clear_bit_unlock(0, &backtrace_flag
);
82 // Dump stacks even for idle CPUs.
83 static bool backtrace_idle
;
84 module_param(backtrace_idle
, bool, 0644);
86 bool nmi_cpu_backtrace(struct pt_regs
*regs
)
88 int cpu
= smp_processor_id();
91 if (cpumask_test_cpu(cpu
, to_cpumask(backtrace_mask
))) {
93 * Allow nested NMI backtraces while serializing
96 printk_cpu_lock_irqsave(flags
);
97 if (!READ_ONCE(backtrace_idle
) && regs
&& cpu_in_idle(instruction_pointer(regs
))) {
98 pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
99 cpu
, (void *)instruction_pointer(regs
));
101 pr_warn("NMI backtrace for cpu %d\n", cpu
);
107 printk_cpu_unlock_irqrestore(flags
);
108 cpumask_clear_cpu(cpu
, to_cpumask(backtrace_mask
));
114 NOKPROBE_SYMBOL(nmi_cpu_backtrace
);