NMI watchdog: fix for lockup detector breakage on resume (45226e94) · Commits · 戴 / test

On the suspend/resume path the boot CPU does not go though an offline->online transition. This breaks the NMI detector post-resume since it depends on PMU state that is lost when the system gets suspended. Fix this by forcing a CPU offline->online transition for the lockup detector on the boot CPU during resume. To provide more context, we enable NMI watchdog on Chrome OS. We have seen several reports of systems freezing up completely which indicated that the NMI watchdog was not firing for some reason. Debugging further, we found a simple way of repro'ing system freezes -- issuing the command 'tasket 1 sh -c "echo nmilockup > /proc/breakme"' after the system has been suspended/resumed one or more times. With this patch in place, the system freeze result in panics, as expected. These panics provide a nice stack trace for us to debug the actual issue causing the freeze. [akpm@linux-foundation.org: fiddle with code comment] [akpm@linux-foundation.org: make lockup_detector_bootcpu_resume() conditional on CONFIG_SUSPEND] [akpm@linux-foundation.org: fix section errors] Signed-off-by:

Sameer Nanda <snanda@chromium.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Don Zickus <dzickus@redhat.com> Cc: Mandeep Singh Baines <msb@chromium.org> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -334,6 +334,14 @@ static inline void lockup_detector_init(void)
		}
		#endif

		#if defined(CONFIG_LOCKUP_DETECTOR) && defined(CONFIG_SUSPEND)
		void lockup_detector_bootcpu_resume(void);
		#else
		static inline void lockup_detector_bootcpu_resume(void)
		{
		}
		#endif

		#ifdef CONFIG_DETECT_HUNG_TASK
		extern unsigned int sysctl_hung_task_panic;
		extern unsigned long sysctl_hung_task_check_count;

kernel/power/suspend.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -178,6 +178,9 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
		arch_suspend_enable_irqs();
		BUG_ON(irqs_disabled());

		/* Kick the lockup detector */
		lockup_detector_bootcpu_resume();

		Enable_cpus:
		enable_nonboot_cpus();

kernel/watchdog.c

+19 −2

Original line number	Diff line number	Diff line
		@@ -575,7 +575,7 @@ out:
		/*
		* Create/destroy watchdog threads as CPUs come and go:
		*/
		static int __cpuinit
		static int
		cpu_callback(struct notifier_block nfb, unsigned long action, void hcpu)
		{
		int hotcpu = (unsigned long)hcpu;
		@@ -610,10 +610,27 @@ cpu_callback(struct notifier_block nfb, unsigned long action, void hcpu)
		return NOTIFY_OK;
		}

		static struct notifier_block __cpuinitdata cpu_nfb = {
		static struct notifier_block cpu_nfb = {
		.notifier_call = cpu_callback
		};

		#ifdef CONFIG_SUSPEND
		/*
		* On exit from suspend we force an offline->online transition on the boot CPU
		* so that the PMU state that was lost while in suspended state gets set up
		* properly for the boot CPU. This information is required for restarting the
		* NMI watchdog.
		*/
		void lockup_detector_bootcpu_resume(void)
		{
		void cpu = (void )(long)smp_processor_id();

		cpu_callback(&cpu_nfb, CPU_DEAD_FROZEN, cpu);
		cpu_callback(&cpu_nfb, CPU_UP_PREPARE_FROZEN, cpu);
		cpu_callback(&cpu_nfb, CPU_ONLINE_FROZEN, cpu);
		}
		#endif

		void __init lockup_detector_init(void)
		{
		void cpu = (void )(long)smp_processor_id();

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