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From: Shijie Huang <shijie@amperemail.onmicrosoft.com>
To: Vincent Guittot <vincent.guittot@linaro.org>,
	Huang Shijie <shijie@os.amperecomputing.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	vschneid@redhat.com, patches@amperecomputing.com, cl@linux.com,
	Shubhang@os.amperecomputing.com, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] sched/fair: do not scan twice in detach_tasks()
Date: Tue, 22 Jul 2025 11:16:17 +0800	[thread overview]
Message-ID: <dac3339d-a721-442f-8638-6e4c493f35db@amperemail.onmicrosoft.com> (raw)
In-Reply-To: <CAKfTPtC7+V6ubaGDPy0MW2MFG7w_yrnYCPQ-b2=3uYgeM+-+EA@mail.gmail.com>


On 2025/7/21 17:40, Vincent Guittot wrote:
> On Mon, 21 Jul 2025 at 04:40, Huang Shijie
> <shijie@os.amperecomputing.com> wrote:
>> detach_tasks() uses struct lb_env.loop_max as an env.src_rq->cfs_tasks
>> iteration count limit. It is however set without the source RQ lock held,
>> and besides detach_tasks() can be re-invoked after releasing and
>> re-acquiring the RQ lock per LBF_NEED_BREAK.
>>
>> This means that env.loop_max and the actual length of env.src_rq->cfs_tasks
>> as observed within detach_tasks() can differ. This can cause some tasks to
> why not setting env.loop_max only once rq lock is taken in this case ?

Yes.  we do it in this way.


Thanks

Huang Shijie



      parent reply	other threads:[~2025-07-22  3:16 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-07-21  2:39 Huang Shijie
2025-07-21  9:40 ` Vincent Guittot
2025-07-21 11:25   ` Valentin Schneider
2025-07-22  3:26     ` Shijie Huang
2025-07-22  7:49     ` Vincent Guittot
2025-07-22  7:53       ` Vincent Guittot
2025-07-22  9:01         ` Valentin Schneider
2025-07-22  9:40         ` Shijie Huang
2025-07-22  3:16   ` Shijie Huang [this message]

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