From 55d6af1d66885059ffc2ac23083de52d12be63bb Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 15 Jul 2021 21:39:54 +0206 Subject: lib/nmi_backtrace: explicitly serialize banner and regs Currently the nmi_backtrace is serialized against other CPUs because the messages are sent to the NMI buffers. Once these buffers are removed, only the dumped stack will be serialized against other CPUs (via the printk_cpu_lock). Also serialize the nmi_backtrace banner and regs using the printk_cpu_lock so that per-CPU serialization will be preserved even after the NMI buffers are removed. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210715193359.25946-2-john.ogness@linutronix.de --- lib/nmi_backtrace.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c index 8abe1870dba4..dae233c5f597 100644 --- a/lib/nmi_backtrace.c +++ b/lib/nmi_backtrace.c @@ -92,17 +92,24 @@ 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))) { 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 { + /* + * Allow nested NMI backtraces while serializing + * against other CPUs. + */ + printk_cpu_lock_irqsave(flags); pr_warn("NMI backtrace for cpu %d\n", cpu); if (regs) show_regs(regs); else dump_stack(); + printk_cpu_unlock_irqrestore(flags); } cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); return true; -- cgit