Messages in this thread Patch in this message | | | Date | Thu, 13 Sep 2018 17:23:07 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH RFC] kernel/hung_task.c: disable on suspend |
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On 09/13, Rafael J. Wysocki wrote: > > 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.
I don't understand your discussion with Vitaly, but shouldn't we make khungtaskd thread freezable anyway?
Oleg.
--- x/kernel/hung_task.c +++ x/kernel/hung_task.c @@ -185,7 +185,7 @@ static void check_hung_uninterruptible_t hung_task_show_lock = false; rcu_read_lock(); for_each_process_thread(g, t) { - if (!max_count--) + if (!max_count-- || freezing(current)) goto unlock; if (!--batch_count) { batch_count = HUNG_TASK_BATCHING; @@ -249,6 +249,7 @@ static int watchdog(void *dummy) { unsigned long hung_last_checked = jiffies; + set_freezable(); set_user_nice(current, 0); for ( ; ; ) { @@ -266,7 +267,7 @@ static int watchdog(void *dummy) hung_last_checked = jiffies; continue; } - schedule_timeout_interruptible(t); + freezable_schedule_timeout_interruptible(t); } return 0;
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