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Message-ID: <CAJZ5v0iJmn4x+zqNhQ4zfYCucnZhYb2hK3o096xPX6Ju2zV2oQ@mail.gmail.com>
Date: Thu, 18 Oct 2018 09:32:42 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Vitaly Kuznetsov <vkuznets@...hat.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Linux PM <linux-pm@...r.kernel.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Paul McKenney <paulmck@...ux.vnet.ibm.com>,
Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v4] kernel/hung_task.c: disable on suspend
On Wed, Oct 17, 2018 at 1:24 PM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> It is possible to observe hung_task complaints when system goes to
> suspend-to-idle state:
>
> # echo freeze > /sys/power/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
>
> Register a PM notifier to disable the detector on suspend and re-enable
> back on wakeup.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Thanks for your patience with this!
Are there any objections or concerns regarding this patch?
> ---
> Changes since v3:
> - Handle PM_RESTORE_PREPARE/PM_POST_RESTORE for completeness
> [Rafael J. Wysocki]
> ---
> kernel/hung_task.c | 30 +++++++++++++++++++++++++++++-
> 1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index b9132d1269ef..cb8e3e8ac7b9 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 +243,28 @@ 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:
> + case PM_HIBERNATION_PREPARE:
> + case PM_RESTORE_PREPARE:
> + hung_detector_suspended = true;
> + break;
> + case PM_POST_SUSPEND:
> + case PM_POST_HIBERNATION:
> + case PM_POST_RESTORE:
> + hung_detector_suspended = false;
> + break;
> + default:
> + break;
> + }
> + return NOTIFY_OK;
> +}
> +
> /*
> * kthread which checks for tasks stuck in D state
> */
> @@ -261,7 +284,8 @@ 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 +299,10 @@ 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;
> --
> 2.17.1
>
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