1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0
2b2c0b2cbSRussell King /*
3b2c0b2cbSRussell King * NMI backtrace support
4b2c0b2cbSRussell King *
5b2c0b2cbSRussell King * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
6b2c0b2cbSRussell King * with the following header:
7b2c0b2cbSRussell King *
8b2c0b2cbSRussell King * HW NMI watchdog support
9b2c0b2cbSRussell King *
10b2c0b2cbSRussell King * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
11b2c0b2cbSRussell King *
12b2c0b2cbSRussell King * Arch specific calls to support NMI watchdog
13b2c0b2cbSRussell King *
14b2c0b2cbSRussell King * Bits copied from original nmi.c file
15b2c0b2cbSRussell King */
16b2c0b2cbSRussell King #include <linux/cpumask.h>
17b2c0b2cbSRussell King #include <linux/delay.h>
18b2c0b2cbSRussell King #include <linux/kprobes.h>
19b2c0b2cbSRussell King #include <linux/nmi.h>
206727ad9eSChris Metcalf #include <linux/cpu.h>
21b17b0153SIngo Molnar #include <linux/sched/debug.h>
22b2c0b2cbSRussell King
239a01c3edSChris Metcalf #ifdef arch_trigger_cpumask_backtrace
24b2c0b2cbSRussell King /* For reliability, we're prepared to waste bits here. */
25b2c0b2cbSRussell King static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
26b2c0b2cbSRussell King
279a01c3edSChris Metcalf /* "in progress" flag of arch_trigger_cpumask_backtrace */
28b2c0b2cbSRussell King static unsigned long backtrace_flag;
29b2c0b2cbSRussell King
300768330dSDaniel Thompson /*
319a01c3edSChris Metcalf * When raise() is called it will be passed a pointer to the
320768330dSDaniel Thompson * backtrace_mask. Architectures that call nmi_cpu_backtrace()
330768330dSDaniel Thompson * directly from their raise() functions may rely on the mask
340768330dSDaniel Thompson * they are passed being updated as a side effect of this call.
350768330dSDaniel Thompson */
nmi_trigger_cpumask_backtrace(const cpumask_t * mask,int exclude_cpu,void (* raise)(cpumask_t * mask))369a01c3edSChris Metcalf void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
37*8d539b84SDouglas Anderson int exclude_cpu,
38b2c0b2cbSRussell King void (*raise)(cpumask_t *mask))
39b2c0b2cbSRussell King {
4042a0bb3fSPetr Mladek int i, this_cpu = get_cpu();
41b2c0b2cbSRussell King
42b2c0b2cbSRussell King if (test_and_set_bit(0, &backtrace_flag)) {
43b2c0b2cbSRussell King /*
44b2c0b2cbSRussell King * If there is already a trigger_all_cpu_backtrace() in progress
45b2c0b2cbSRussell King * (backtrace_flag == 1), don't output double cpu dump infos.
46b2c0b2cbSRussell King */
47b2c0b2cbSRussell King put_cpu();
48b2c0b2cbSRussell King return;
49b2c0b2cbSRussell King }
50b2c0b2cbSRussell King
519a01c3edSChris Metcalf cpumask_copy(to_cpumask(backtrace_mask), mask);
52*8d539b84SDouglas Anderson if (exclude_cpu != -1)
53*8d539b84SDouglas Anderson cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask));
54b2c0b2cbSRussell King
5567766489SChris Metcalf /*
5667766489SChris Metcalf * Don't try to send an NMI to this cpu; it may work on some
5767766489SChris Metcalf * architectures, but on others it may not, and we'll get
5867766489SChris Metcalf * information at least as useful just by doing a dump_stack() here.
5967766489SChris Metcalf * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
6067766489SChris Metcalf */
6167766489SChris Metcalf if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
6267766489SChris Metcalf nmi_cpu_backtrace(NULL);
6367766489SChris Metcalf
64b2c0b2cbSRussell King if (!cpumask_empty(to_cpumask(backtrace_mask))) {
659a01c3edSChris Metcalf pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
669a01c3edSChris Metcalf this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
67344da544SPaul E. McKenney nmi_backtrace_stall_snap(to_cpumask(backtrace_mask));
68b2c0b2cbSRussell King raise(to_cpumask(backtrace_mask));
69b2c0b2cbSRussell King }
70b2c0b2cbSRussell King
71b2c0b2cbSRussell King /* Wait for up to 10 seconds for all CPUs to do the backtrace */
72b2c0b2cbSRussell King for (i = 0; i < 10 * 1000; i++) {
73b2c0b2cbSRussell King if (cpumask_empty(to_cpumask(backtrace_mask)))
74b2c0b2cbSRussell King break;
75b2c0b2cbSRussell King mdelay(1);
76b2c0b2cbSRussell King touch_softlockup_watchdog();
77b2c0b2cbSRussell King }
78344da544SPaul E. McKenney nmi_backtrace_stall_check(to_cpumask(backtrace_mask));
79b2c0b2cbSRussell King
805d5e4522SNicholas Piggin /*
815d5e4522SNicholas Piggin * Force flush any remote buffers that might be stuck in IRQ context
825d5e4522SNicholas Piggin * and therefore could not run their irq_work.
835d5e4522SNicholas Piggin */
845d5e4522SNicholas Piggin printk_trigger_flush();
855d5e4522SNicholas Piggin
8642a0bb3fSPetr Mladek clear_bit_unlock(0, &backtrace_flag);
87b2c0b2cbSRussell King put_cpu();
88b2c0b2cbSRussell King }
89b2c0b2cbSRussell King
90160c7ba3SPaul E. McKenney // Dump stacks even for idle CPUs.
91160c7ba3SPaul E. McKenney static bool backtrace_idle;
92160c7ba3SPaul E. McKenney module_param(backtrace_idle, bool, 0644);
93160c7ba3SPaul E. McKenney
nmi_cpu_backtrace(struct pt_regs * regs)94b2c0b2cbSRussell King bool nmi_cpu_backtrace(struct pt_regs *regs)
95b2c0b2cbSRussell King {
96b2c0b2cbSRussell King int cpu = smp_processor_id();
9755d6af1dSJohn Ogness unsigned long flags;
98b2c0b2cbSRussell King
99b2c0b2cbSRussell King if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
10055d6af1dSJohn Ogness /*
10155d6af1dSJohn Ogness * Allow nested NMI backtraces while serializing
10255d6af1dSJohn Ogness * against other CPUs.
10355d6af1dSJohn Ogness */
104faebd693SJohn Ogness printk_cpu_sync_get_irqsave(flags);
10526d1982fSPetr Mladek if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
10626d1982fSPetr Mladek pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
10726d1982fSPetr Mladek cpu, (void *)instruction_pointer(regs));
10826d1982fSPetr Mladek } else {
109b2c0b2cbSRussell King pr_warn("NMI backtrace for cpu %d\n", cpu);
1100768330dSDaniel Thompson if (regs)
111b2c0b2cbSRussell King show_regs(regs);
1120768330dSDaniel Thompson else
1130768330dSDaniel Thompson dump_stack();
1146727ad9eSChris Metcalf }
115faebd693SJohn Ogness printk_cpu_sync_put_irqrestore(flags);
116b2c0b2cbSRussell King cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
117b2c0b2cbSRussell King return true;
118b2c0b2cbSRussell King }
119b2c0b2cbSRussell King
120b2c0b2cbSRussell King return false;
121b2c0b2cbSRussell King }
122b2c0b2cbSRussell King NOKPROBE_SYMBOL(nmi_cpu_backtrace);
123b2c0b2cbSRussell King #endif
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