Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH RFC] kernel/hung_task.c: disable on suspend | Date | Thu, 13 Sep 2018 10:47:08 +0200 |
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"Rafael J. Wysocki" <rafael@kernel.org> writes:
> On Wed, Sep 12, 2018 at 6:11 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote: >> >> It is possible to observe hung_task complaints when system goes to >> suspend-to-idle state: >> >> PM: Syncing filesystems ... done. >> Freezing user space processes ... (elapsed 0.001 seconds) done. >> OOM killer disabled. >> Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done. >> sd 0:0:0:0: [sda] Synchronizing SCSI cache >> INFO: task bash:1569 blocked for more than 120 seconds. >> Not tainted 4.19.0-rc3_+ #687 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> bash D 0 1569 604 0x00000000 >> Call Trace: >> ? __schedule+0x1fe/0x7e0 >> schedule+0x28/0x80 >> suspend_devices_and_enter+0x4ac/0x750 >> pm_suspend+0x2c0/0x310 > > This actually is a good catch, but the problem is related to what > happens to the monotonic clock during suspend to idle. > > The clock issue needs to be addressed anyway IMO and then this problem > will go away automatically.
Do I understand it correctly that the suggestion is to fully suspend monothonic clock in s2idle (and don't advance it after resume)?
> >> Register a PM notifier to disable the detector on suspend and re-enable >> back on wakeup. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> --- >> RFC: It really makes me wonder why nobody reported this before, makes >> me think I'm missing something. >> --- >> kernel/hung_task.c | 26 +++++++++++++++++++++++++- >> 1 file changed, 25 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/hung_task.c b/kernel/hung_task.c >> index b9132d1269ef..d75f288c016f 100644 >> --- a/kernel/hung_task.c >> +++ b/kernel/hung_task.c >> @@ -15,6 +15,7 @@ >> #include <linux/lockdep.h> >> #include <linux/export.h> >> #include <linux/sysctl.h> >> +#include <linux/suspend.h> >> #include <linux/utsname.h> >> #include <linux/sched/signal.h> >> #include <linux/sched/debug.h> >> @@ -242,6 +243,24 @@ void reset_hung_task_detector(void) >> } >> EXPORT_SYMBOL_GPL(reset_hung_task_detector); >> >> +static bool hung_detector_suspended; >> + >> +static int hungtask_pm_notify(struct notifier_block *self, >> + unsigned long action, void *hcpu) >> +{ >> + switch (action) { >> + case PM_SUSPEND_PREPARE: > > You'd want PM_HIBERNATION_PREPARE here too I think. > >> + hung_detector_suspended = true; >> + break; >> + case PM_POST_SUSPEND: > > And PM_POST_HIBERNATION here for consistency. >
Sure, will do in v1.
>> + hung_detector_suspended = false; >> + break; >> + default: >> + break; >> + } >> + return NOTIFY_OK; >> +} >> + >> /* >> * kthread which checks for tasks stuck in D state >> */ >> @@ -261,7 +280,8 @@ static int watchdog(void *dummy) >> interval = min_t(unsigned long, interval, timeout); >> t = hung_timeout_jiffies(hung_last_checked, interval); >> if (t <= 0) { >> - if (!atomic_xchg(&reset_hung_task, 0)) >> + if (!atomic_xchg(&reset_hung_task, 0) && >> + !hung_detector_suspended) >> check_hung_uninterruptible_tasks(timeout); >> hung_last_checked = jiffies; >> continue; >> @@ -275,6 +295,10 @@ static int watchdog(void *dummy) >> static int __init hung_task_init(void) >> { >> atomic_notifier_chain_register(&panic_notifier_list, &panic_block); >> + >> + /* Disable hung task detector on suspend */ >> + pm_notifier(hungtask_pm_notify, 0); >> + >> watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); >> >> return 0; >> -- >> 2.14.4 >>
-- Vitaly
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