From: Valentin Schneider <valentin.schneider@arm.com>
To: Tao Zhou <ouwen210@hotmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vincent.donnefort@arm.com, tj@kernel.org
Subject: Re: [PATCH v3 10/19] sched: Fix migrate_disable() vs set_cpus_allowed_ptr()
Date: Mon, 19 Oct 2020 18:36:16 +0100 [thread overview]
Message-ID: <jhjblgyqfsf.mognet@arm.com> (raw)
In-Reply-To: <BN8PR12MB2978F76887133CCA2102B7589A1E0@BN8PR12MB2978.namprd12.prod.outlook.com>
On 19/10/20 17:32, Tao Zhou wrote:
> Hi Valentin,
>>
>> Side thought: don't we need to NULL p->migration_pending in __sched_fork()?
>>
>
> No need, if fork happen, the forked task will inherit that pending.
Which is what I'm worrying about. I think we can ignore migrate_disable()
for now and just consider a task fork()'ing while another tries to
sched_setaffinity() it; say the fork() happens just after the pending has
been installed.
Unless I'm overthinking it, we could end up with a dangling pending
reference, which will wreck havock to any later affine_move_task() (see the
if (p->migration_pending) paths).
> If pending is NULL, when call SCA, it will install pending. If pending
> is not NULL, it means it is in migrate region and wait for complete.
> If NULL pending in __sched_fork() it will install a new pending in this
> case which is not right to me. Add a flag(ENABLE_MIGRATE) to arg will
> differ the path where in.
>
> Always likely miss something.
>
> Tao
>
next prev parent reply other threads:[~2020-10-19 17:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 11:05 [PATCH v3 00/19] sched: Migrate disable support Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 01/19] stop_machine: Add function and caller debug info Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 02/19] sched: Fix balance_callback() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 03/19] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 04/19] sched/core: Wait for tasks being pushed away on hotplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 05/19] workqueue: Manually break affinity " Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 06/19] sched/hotplug: Consolidate task migration on CPU unplug Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 07/19] sched: Fix hotplug vs CPU bandwidth control Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 08/19] sched: Massage set_cpus_allowed() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 09/19] sched: Add migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 10/19] sched: Fix migrate_disable() vs set_cpus_allowed_ptr() Peter Zijlstra
2020-10-15 13:54 ` Valentin Schneider
2020-10-15 14:19 ` Peter Zijlstra
2020-10-16 12:48 ` Valentin Schneider
[not found] ` <BN8PR12MB29784D239007D0D6CA3F4F2A9A010@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-18 15:51 ` Valentin Schneider
[not found] ` <BN8PR12MB2978F76887133CCA2102B7589A1E0@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-19 17:36 ` Valentin Schneider [this message]
[not found] ` <BN8PR12MB2978D36FF4A81C344DCF37FD9A1F0@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-20 7:56 ` Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 11/19] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
[not found] ` <BN8PR12MB2978A3BB8062DF4CEEB184109A030@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-10-16 9:35 ` Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 12/19] sched,rt: Use cpumask_any*_distribute() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 13/19] sched,rt: Use the full cpumask for balancing Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 14/19] sched, lockdep: Annotate ->pi_lock recursion Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 15/19] sched: Fix migrate_disable() vs rt/dl balancing Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 16/19] sched/proc: Print accurate cpumask vs migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 17/19] sched: Add migrate_disable() tracepoints Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 18/19] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() Peter Zijlstra
2020-10-15 11:05 ` [PATCH v3 19/19] sched: Comment affine_move_task() Peter Zijlstra
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