lib: Add backtrace_idle parameter to force backtrace of idle CPUs (160c7ba3) · Commits · 戴 / test

Currently, the nmi_cpu_backtrace() declines to produce backtraces for idle CPUs. This is a good choice in the common case in which problems are caused only by non-idle CPUs. However, there are occasionally situations in which idle CPUs are helping to cause problems. This commit therefore adds an nmi_backtrace.backtrace_idle kernel boot parameter that causes nmi_cpu_backtrace() to dump stacks even of idle CPUs. Signed-off-by:

Paul E. McKenney <paulmck@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <linux-doc@vger.kernel.org>

Documentation/admin-guide/kernel-parameters.txt

+4 −0

Original line number	Diff line number	Diff line
		@@ -3073,6 +3073,10 @@
		and gids from such clients. This is intended to ease
		migration from NFSv2/v3.

		nmi_backtrace.backtrace_idle [KNL]
		Dump stacks even of idle CPUs in response to an
		NMI stack-backtrace request.

		nmi_debug= [KNL,SH] Specify one or more actions to take
		when a NMI is triggered.
		Format: [state][,regs][,debounce][,die]

lib/nmi_backtrace.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -85,12 +85,16 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
		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();

		if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
		if (regs && cpu_in_idle(instruction_pointer(regs))) {
		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 {

Admin message