From: Patrick Bellasi <patrick.bellasi@matbug.net>
To: Quentin Perret <qperret@google.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
ctheegal@codeaurora.org, dianders@chromium.org,
valentin.schneider@arm.com, qais.yousef@arm.com,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH] sched/core: Fix reset-on-fork from RT with uclamp
Date: Tue, 14 Apr 2020 19:21:20 +0200 [thread overview]
Message-ID: <20200414172120.GA20442@darkstar> (raw)
In-Reply-To: <20200414161320.251897-1-qperret@google.com>
On 14-Apr 17:13, Quentin Perret wrote:
> uclamp_fork() resets the uclamp values to their default when the
> reset-on-fork flag is set. It also checks whether the task has a RT
> policy, and sets its uclamp.min to 1024 accordingly. However, during
> reset-on-fork, the task's policy is lowered to SCHED_NORMAL right after,
> hence leading to an erroneous uclamp.min setting for the new task if it
> was forked from RT.
Right, good catch. Thanks.
> Fix this by removing the unnecessary check on rt_policy() in
> uclamp_fork() as this doesn't make sense if the reset-on-fork flag is
> set.
>
> Reported-by: Chitti Babu Theegala <ctheegal@codeaurora.org>
> Signed-off-by: Quentin Perret <qperret@google.com>
Fixes: 1a00d999971c ("sched/uclamp: Set default clamps for RT tasks")
Reviewed-by: Patrick Bellasi <patrick.bellasi@matbug.net>
> ---
> kernel/sched/core.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3a61a3b8eaa9..9ea3e484eea2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1234,10 +1234,6 @@ static void uclamp_fork(struct task_struct *p)
> for_each_clamp_id(clamp_id) {
> unsigned int clamp_value = uclamp_none(clamp_id);
>
> - /* By default, RT tasks always get 100% boost */
> - if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
> - clamp_value = uclamp_none(UCLAMP_MAX);
> -
> uclamp_se_set(&p->uclamp_req[clamp_id], clamp_value, false);
> }
> }
> --
> 2.26.0.110.g2183baf09c-goog
>
--
#include <best/regards.h>
Patrick Bellasi
next prev parent reply other threads:[~2020-04-14 17:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-14 16:13 [PATCH] sched/core: Fix reset-on-fork from RT with uclamp Quentin Perret
2020-04-14 16:21 ` Joel Fernandes
2020-04-14 16:27 ` Quentin Perret
2020-04-14 16:32 ` Joel Fernandes
2020-04-14 17:21 ` Patrick Bellasi [this message]
2020-04-14 17:25 ` Quentin Perret
2020-04-14 20:45 ` Doug Anderson
2020-04-15 8:20 ` Quentin Perret
2020-04-15 16:31 ` Doug Anderson
2020-04-15 17:47 ` Patrick Bellasi
2020-04-16 8:54 ` Quentin Perret
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