diff options
Diffstat (limited to 'lib/nmi_backtrace.c')
| -rw-r--r-- | lib/nmi_backtrace.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c new file mode 100644 index 0000000000..33c154264b --- /dev/null +++ b/lib/nmi_backtrace.c @@ -0,0 +1,123 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * NMI backtrace support + * + * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King, + * with the following header: + * + * HW NMI watchdog support + * + * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. + * + * Arch specific calls to support NMI watchdog + * + * Bits copied from original nmi.c file + */ +#include <linux/cpumask.h> +#include <linux/delay.h> +#include <linux/kprobes.h> +#include <linux/nmi.h> +#include <linux/cpu.h> +#include <linux/sched/debug.h> + +#ifdef arch_trigger_cpumask_backtrace +/* For reliability, we're prepared to waste bits here. */ +static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; + +/* "in progress" flag of arch_trigger_cpumask_backtrace */ +static unsigned long backtrace_flag; + +/* + * When raise() is called it will be passed a pointer to the + * backtrace_mask. Architectures that call nmi_cpu_backtrace() + * directly from their raise() functions may rely on the mask + * they are passed being updated as a side effect of this call. + */ +void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, + int exclude_cpu, + void (*raise)(cpumask_t *mask)) +{ + int i, this_cpu = get_cpu(); + + if (test_and_set_bit(0, &backtrace_flag)) { + /* + * If there is already a trigger_all_cpu_backtrace() in progress + * (backtrace_flag == 1), don't output double cpu dump infos. + */ + put_cpu(); + return; + } + + cpumask_copy(to_cpumask(backtrace_mask), mask); + if (exclude_cpu != -1) + cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask)); + + /* + * Don't try to send an NMI to this cpu; it may work on some + * architectures, but on others it may not, and we'll get + * information at least as useful just by doing a dump_stack() here. + * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit. + */ + if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask))) + nmi_cpu_backtrace(NULL); + + if (!cpumask_empty(to_cpumask(backtrace_mask))) { + pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n", + this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask)); + nmi_backtrace_stall_snap(to_cpumask(backtrace_mask)); + raise(to_cpumask(backtrace_mask)); + } + + /* Wait for up to 10 seconds for all CPUs to do the backtrace */ + for (i = 0; i < 10 * 1000; i++) { + if (cpumask_empty(to_cpumask(backtrace_mask))) + break; + mdelay(1); + touch_softlockup_watchdog(); + } + nmi_backtrace_stall_check(to_cpumask(backtrace_mask)); + + /* + * Force flush any remote buffers that might be stuck in IRQ context + * and therefore could not run their irq_work. + */ + printk_trigger_flush(); + + clear_bit_unlock(0, &backtrace_flag); + put_cpu(); +} + +// Dump stacks even for idle CPUs. +static bool backtrace_idle; +module_param(backtrace_idle, bool, 0644); + +bool nmi_cpu_backtrace(struct pt_regs *regs) +{ + int cpu = smp_processor_id(); + unsigned long flags; + + if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { + /* + * Allow nested NMI backtraces while serializing + * against other CPUs. + */ + printk_cpu_sync_get_irqsave(flags); + if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) { + pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n", + cpu, (void *)instruction_pointer(regs)); + } else { + pr_warn("NMI backtrace for cpu %d\n", cpu); + if (regs) + show_regs(regs); + else + dump_stack(); + } + printk_cpu_sync_put_irqrestore(flags); + cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); + return true; + } + + return false; +} +NOKPROBE_SYMBOL(nmi_cpu_backtrace); +#endif |