linux-kernel - Re: [PATCH v3] freezer, sched: report the frozen task stat as 'D'

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Message-ID: <20241217120419.GA2354@noisy.programming.kicks-ass.net>
Date: Tue, 17 Dec 2024 13:04:19 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, tj@...nel.org,
	mkoutny@...e.com, roman.gushchin@...ux.dev,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	chenridong@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH v3] freezer, sched: report the frozen task stat as 'D'

On Tue, Dec 17, 2024 at 12:48:18AM +0000, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
> 
> Before the commit f5d39b020809 ("freezer,sched: Rewrite core freezer
> logic"), the frozen task stat was reported as 'D' in cgroup v1.
> However, after rewriting core freezer logic, the frozen task stat is
> reported as 'R'. This is confusing, especially when a task with stat of
> 'S' is frozen.
> 
> This can be reproduced as bellow step:
> cd /sys/fs/cgroup/freezer/
> mkdir test
> sleep 1000 &
> [1] 739         // task whose stat is 'S'
> echo 739 > test/cgroup.procs
> echo FROZEN > test/freezer.state
> ps -aux | grep 739
> root     739  0.1  0.0   8376  1812 pts/0    R    10:56   0:00 sleep 1000
> 
> As shown above, a task whose stat is 'S' was changed to 'R' when it was
> frozen. To solve this issue, simply maintain the same reported state as
> before the rewrite.
> 
> Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> Acked-by: Tejun Heo <tj@...nel.org>

Thanks!