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Message-ID: <20230927080850.GB21824@noisy.programming.kicks-ass.net>
Date: Wed, 27 Sep 2023 10:08:50 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Kuyo Chang <kuyo.chang@...iatek.com>
Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>,
wsd_upstream@...iatek.com, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 1/1] sched/core: Fix stuck on completion for
affine_move_task() when stopper disable
On Wed, Sep 27, 2023 at 11:34:28AM +0800, Kuyo Chang wrote:
> From: kuyo chang <kuyo.chang@...iatek.com>
>
> [Syndrome] hung detect shows below warning msg
> [ 4320.666557] [ T56] khungtaskd: [name:hung_task&]INFO: task stressapptest:17803 blocked for more than 3600 seconds.
> [ 4320.666589] [ T56] khungtaskd: [name:core&]task:stressapptest state:D stack:0 pid:17803 ppid:17579 flags:0x04000008
> [ 4320.666601] [ T56] khungtaskd: Call trace:
> [ 4320.666607] [ T56] khungtaskd: __switch_to+0x17c/0x338
> [ 4320.666642] [ T56] khungtaskd: __schedule+0x54c/0x8ec
> [ 4320.666651] [ T56] khungtaskd: schedule+0x74/0xd4
> [ 4320.666656] [ T56] khungtaskd: schedule_timeout+0x34/0x108
> [ 4320.666672] [ T56] khungtaskd: do_wait_for_common+0xe0/0x154
> [ 4320.666678] [ T56] khungtaskd: wait_for_completion+0x44/0x58
> [ 4320.666681] [ T56] khungtaskd: __set_cpus_allowed_ptr_locked+0x344/0x730
> [ 4320.666702] [ T56] khungtaskd: __sched_setaffinity+0x118/0x160
> [ 4320.666709] [ T56] khungtaskd: sched_setaffinity+0x10c/0x248
> [ 4320.666715] [ T56] khungtaskd: __arm64_sys_sched_setaffinity+0x15c/0x1c0
> [ 4320.666719] [ T56] khungtaskd: invoke_syscall+0x3c/0xf8
> [ 4320.666743] [ T56] khungtaskd: el0_svc_common+0xb0/0xe8
> [ 4320.666749] [ T56] khungtaskd: do_el0_svc+0x28/0xa8
> [ 4320.666755] [ T56] khungtaskd: el0_svc+0x28/0x9c
> [ 4320.666761] [ T56] khungtaskd: el0t_64_sync_handler+0x7c/0xe4
> [ 4320.666766] [ T56] khungtaskd: el0t_64_sync+0x18c/0x190
>
> [Analysis]
>
> After add some debug footprint massage, this issue happened at stopper
> disable case.
> It cannot exec migration_cpu_stop fun to complete migration.
> This will cause stuck on wait_for_completion.
How did you get in this situation?
> Signed-off-by: kuyo chang <kuyo.chang@...iatek.com>
> ---
> kernel/sched/core.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1dc0b0287e30..98c217a1caa0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3041,8 +3041,9 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
> task_rq_unlock(rq, p, rf);
>
> if (!stop_pending) {
> - stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
> - &pending->arg, &pending->stop_work);
> + if (!stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
> + &pending->arg, &pending->stop_work))
> + return -ENOENT;
And -ENOENT is the right return code for when the target CPU is not
available?
I suspect you're missing more than halp the picture and this is a
band-aid solution at best. Please try harder.
> }
>
> if (flags & SCA_MIGRATE_ENABLE)
> --
> 2.18.0
>
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