From: Quentin Perret <qperret@google.com>
To: mingo@redhat.com, peterz@infradead.org,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
qais.yousef@arm.com, rickyiu@google.com, wvw@google.com,
patrick.bellasi@matbug.net
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH] sched: Fix UCLAMP_FLAG_IDLE setting
Date: Wed, 9 Jun 2021 14:37:04 +0000 [thread overview]
Message-ID: <YMDSEHB5+zlajb4x@google.com> (raw)
In-Reply-To: <20210609143339.1194238-1-qperret@google.com>
On Wednesday 09 Jun 2021 at 14:33:39 (+0000), Quentin Perret wrote:
> The UCLAMP_FLAG_IDLE flag is set on a runqueue when dequeueing the last
> active task to maintain the last uclamp.max and prevent blocked util
> from suddenly becoming visible.
>
> However, there is an asymmetry in how the flag is set and cleared which
> can lead to having the flag set whilst there are active task on the rq.
> Specifically, the flag is set in the uclamp_rq_inc() path, which is
> called at enqueue time, but cleared in the uclamp_rq_dec_id() which is
> called both when dequeueing and task _and_ during cgroup migrations.
>
> Fix this by setting the flag in the uclamp_rq_inc_id() path to ensure
> things remain symmetrical.
>
> Reported-by: Rick Yiu <rickyiu@google.com>
> Signed-off-by: Quentin Perret <qperret@google.com>
Argh, and I think this wants
Fixes: e496187da710 ("sched/uclamp: Enforce last task's UCLAMP_MAX")
next prev parent reply other threads:[~2021-06-09 14:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 14:33 [PATCH] sched: Fix UCLAMP_FLAG_IDLE setting Quentin Perret
2021-06-09 14:37 ` Quentin Perret [this message]
2021-06-10 10:00 ` Qais Yousef
2021-06-10 10:27 ` Quentin Perret
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