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Date:   Tue, 6 Sep 2022 22:50:28 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Waiman Long <longman@redhat.com>
Cc:     Tejun Heo <tj@kernel.org>,
        Jing-Ting Wu <jing-ting.wu@mediatek.com>,
        Mukesh Ojha <quic_mojha@quicinc.com>,
        Valentin Schneider <vschneid@redhat.com>,
        wsd_upstream@mediatek.com, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, Jonathan.JMChen@mediatek.com,
        "chris.redpath@arm.com" <chris.redpath@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Vincent Donnefort <vdonnefort@gmail.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Christian Brauner <brauner@kernel.org>,
        cgroups@vger.kernel.org, lixiong.liu@mediatek.com,
        wenju.xu@mediatek.com
Subject: Re: BUG: HANG_DETECT waiting for migration_cpu_stop() complete
Message-ID: <YxeylMvgc/wKcJqk@hirez.programming.kicks-ass.net>
References: <88b2910181bda955ac46011b695c53f7da39ac47.camel@mediatek.com>
 <b605c3ec-94ab-a55f-5825-9b370d77ecf3@quicinc.com>
 <203d4614c1b2a498a240ace287156e9f401d5395.camel@mediatek.com>
 <YxeR0RoiTdm8sWCJ@slm.duckdns.org>
 <02b8e7b3-941d-8bb9-cd0e-992738893ba3@redhat.com>
 <36a73401-7011-834a-7949-c65a2f66246c@redhat.com>
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On Tue, Sep 06, 2022 at 04:40:03PM -0400, Waiman Long wrote:

I've not followed the earlier stuff due to being unreadable; just
reacting to this..

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 838623b68031..5d9ea1553ec0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2794,9 +2794,9 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
>                 if (cpumask_equal(&p->cpus_mask, new_mask))
>                         goto out;
> 
> -               if (WARN_ON_ONCE(p == current &&
> -                                is_migration_disabled(p) &&
> -                                !cpumask_test_cpu(task_cpu(p), new_mask)))
> {
> +               if (is_migration_disabled(p) &&
> +                   !cpumask_test_cpu(task_cpu(p), new_mask)) {
> +                       WARN_ON_ONCE(p == current);
>                         ret = -EBUSY;
>                         goto out;
>                 }
> @@ -2818,7 +2818,11 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
>         if (flags & SCA_USER)
>                 user_mask = clear_user_cpus_ptr(p);
> 
> -       ret = affine_move_task(rq, p, rf, dest_cpu, flags);
> +       if (!is_migration_disabled(p) || (flags & SCA_MIGRATE_ENABLE)) {
> +               ret = affine_move_task(rq, p, rf, dest_cpu, flags);
> +       } else {
> +               task_rq_unlock(rq, p, rf);
> +       }

This cannot be right. There might be previous set_cpus_allowed_ptr()
callers that are blocked and waiting for the task to land on a valid
CPU.


From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 6 Sep 2022 22:50:28 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, Jing-Ting Wu <jing-ting.wu@mediatek.com>,
	Mukesh Ojha <quic_mojha@quicinc.com>,
	Valentin Schneider <vschneid@redhat.com>, wsd_upstream@mediatek.com,
	linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org, Jonathan.JMChen@mediatek.com,
	"chris.redpath@arm.com" <chris.redpath@arm.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Vincent Donnefort <vdonnefort@gmail.com>,
	Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Christian Brauner <brauner@kernel.org>, cgroups@vger.kernel.org,
	lixiong.liu@mediatek.com, wenju.xu@mediatek.com
Subject: Re: BUG: HANG_DETECT waiting for migration_cpu_stop() complete
Message-ID: <YxeylMvgc/wKcJqk@hirez.programming.kicks-ass.net>
References: <88b2910181bda955ac46011b695c53f7da39ac47.camel@mediatek.com>
 <b605c3ec-94ab-a55f-5825-9b370d77ecf3@quicinc.com>
 <203d4614c1b2a498a240ace287156e9f401d5395.camel@mediatek.com>
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 <02b8e7b3-941d-8bb9-cd0e-992738893ba3@redhat.com>
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On Tue, Sep 06, 2022 at 04:40:03PM -0400, Waiman Long wrote:

I've not followed the earlier stuff due to being unreadable; just
reacting to this..

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 838623b68031..5d9ea1553ec0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2794,9 +2794,9 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (cpumask_equal(&p->cpus_=
mask, new_mask))
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 got=
o out;
> =

> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (WARN_ON_ONCE(p =3D=3D cur=
rent &&
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 is_migration_disabled(p) &&
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 !cpumask_test_cpu(task_cpu(p), new_mask)))
> {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (is_migration_disabled(p) =
&&
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 !cpumask_test_cpu=
(task_cpu(p), new_mask)) {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 WARN_=
ON_ONCE(p =3D=3D current);
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret=
 =3D -EBUSY;
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 got=
o out;
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 }
> @@ -2818,7 +2818,11 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
> =A0=A0=A0=A0=A0=A0=A0 if (flags & SCA_USER)
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 user_mask =3D clear_user_cp=
us_ptr(p);
> =

> -=A0=A0=A0=A0=A0=A0 ret =3D affine_move_task(rq, p, rf, dest_cpu, flags);
> +=A0=A0=A0=A0=A0=A0 if (!is_migration_disabled(p) || (flags & SCA_MIGRATE=
_ENABLE)) {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret =3D affine_move_task(rq, =
p, rf, dest_cpu, flags);
> +=A0=A0=A0=A0=A0=A0 } else {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 task_rq_unlock(rq, p, rf);
> +=A0=A0=A0=A0=A0=A0 }

This cannot be right. There might be previous set_cpus_allowed_ptr()
callers that are blocked and waiting for the task to land on a valid
CPU.


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: BUG: HANG_DETECT waiting for migration_cpu_stop() complete
Date: Tue, 6 Sep 2022 22:50:28 +0200
Message-ID: <YxeylMvgc/wKcJqk@hirez.programming.kicks-ass.net>
References: <88b2910181bda955ac46011b695c53f7da39ac47.camel@mediatek.com>
 <b605c3ec-94ab-a55f-5825-9b370d77ecf3@quicinc.com>
 <203d4614c1b2a498a240ace287156e9f401d5395.camel@mediatek.com>
 <YxeR0RoiTdm8sWCJ@slm.duckdns.org>
 <02b8e7b3-941d-8bb9-cd0e-992738893ba3@redhat.com>
 <36a73401-7011-834a-7949-c65a2f66246c@redhat.com>
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To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Jing-Ting Wu <jing-ting.wu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>, Mukesh Ojha <quic_mojha-jfJNa2p1gH1BDgjK7y7TUQ@public.gmane.org>, Valentin Schneider <vschneid-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, wsd_upstream-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Jonathan.JMChen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, "chris.redpath-5wv7dgnIgG8@public.gmane.org" <chris.redpath-5wv7dgnIgG8@public.gmane.org>, Dietmar Eggemann <dietmar.eggemann-5wv7dgnIgG8@public.gmane.org>, Vincent Donnefort <vdonnefort-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Vincent Guittot <vincent.guittot-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Ben Segall <bsegall-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>, Christian Brauner <brauner-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lixiong.liu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, wenju.xu

On Tue, Sep 06, 2022 at 04:40:03PM -0400, Waiman Long wrote:

I've not followed the earlier stuff due to being unreadable; just
reacting to this..

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 838623b68031..5d9ea1553ec0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2794,9 +2794,9 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (cpumask_equal(&p->cpus_=
mask, new_mask))
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 got=
o out;
>=20
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (WARN_ON_ONCE(p =3D=3D cur=
rent &&
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 is_migration_disabled(p) &&
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 !cpumask_test_cpu(task_cpu(p), new_mask)))
> {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (is_migration_disabled(p) =
&&
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 !cpumask_test_cpu=
(task_cpu(p), new_mask)) {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 WARN_=
ON_ONCE(p =3D=3D current);
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret=
 =3D -EBUSY;
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 got=
o out;
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 }
> @@ -2818,7 +2818,11 @@ static int __set_cpus_allowed_ptr_locked(struct
> task_struct *p,
> =A0=A0=A0=A0=A0=A0=A0 if (flags & SCA_USER)
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 user_mask =3D clear_user_cp=
us_ptr(p);
>=20
> -=A0=A0=A0=A0=A0=A0 ret =3D affine_move_task(rq, p, rf, dest_cpu, flags);
> +=A0=A0=A0=A0=A0=A0 if (!is_migration_disabled(p) || (flags & SCA_MIGRATE=
_ENABLE)) {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret =3D affine_move_task(rq, =
p, rf, dest_cpu, flags);
> +=A0=A0=A0=A0=A0=A0 } else {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 task_rq_unlock(rq, p, rf);
> +=A0=A0=A0=A0=A0=A0 }

This cannot be right. There might be previous set_cpus_allowed_ptr()
callers that are blocked and waiting for the task to land on a valid
CPU.