commit 8d451690 ("watchdog: Fix CPU hotplug regression") cause
an oops or hard lockup when doingecho 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog and the kernel is booted with nmi_watchdog=1 (default) Running laptop-mode-tools and disconnecting/connecting AC power will cause this to trigger, making it a common failure scenario on laptops. Instead of bailing out of watchdog_disable() when !watchdog_enabled we can initialize the hrtimer regardless of watchdog_enabled status. This makes it safe to call watchdog_disable() in the nmi_watchdog=0 case, without the negative effect on the enabled => disabled => enabled case. All these tests pass with this patch: - nmi_watchdog=1 echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog - nmi_watchdog=0 echo 0 > /sys/devices/system/cpu/cpu1/online - nmi_watchdog=0 echo mem > /sys/power/state Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51661 Cc: <sta...@vger.kernel.org> # v3.7 Cc: Norbert Warmuth <nwarm...@t-online.de> Cc: Joseph Salisbury <joseph.salisb...@canonical.com> Cc: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Bjørn Mork <bj...@mork.no> --- Hello Linus, This post v3.7-rc8 regression kills any machine with laptop-mode-tools using default config, making it somewhat critical to get a fix into the v3.7.x stable series ASAP. I was hoping for some response from Thomas or the reporters of the original bug, either verifying that my proposal is OK or providing a better fix. But I believe that this cannot wait much longer. Please apply. Thanks, Bjørn Patch history: v3: added Bugzilla reference and additional recipients rebased on current mainline v2: implemented an alternate workaround for the original problem. v1: plain revert of 8d451690 kernel/watchdog.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 997c6a1..75a2ab3 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -344,6 +344,10 @@ static void watchdog_enable(unsigned int cpu) { struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); + /* kick off the timer for the hardlockup detector */ + hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer->function = watchdog_timer_fn; + if (!watchdog_enabled) { kthread_park(current); return; @@ -352,10 +356,6 @@ static void watchdog_enable(unsigned int cpu) /* Enable the perf event */ watchdog_nmi_enable(cpu); - /* kick off the timer for the hardlockup detector */ - hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - hrtimer->function = watchdog_timer_fn; - /* done here because hrtimer_start can only pin to smp_processor_id() */ hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL_PINNED); @@ -369,9 +369,6 @@ static void watchdog_disable(unsigned int cpu) { struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); - if (!watchdog_enabled) - return; - watchdog_set_prio(SCHED_NORMAL, 0); hrtimer_cancel(hrtimer); /* disable the perf event */ -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
