linux-kernel - Re: [PATCH next] sched,freezer: prevent tasks from escaping being frozen

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Message-ID: <9c1a5188-5eb9-4169-afa4-2e4d1819e423@huaweicloud.com>
Date: Fri, 11 Jul 2025 08:51:25 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Michal Koutný <mkoutny@...e.com>,
 Peter Zijlstra <peterz@...radead.org>
Cc: Peter Zijlstra <peterz@...radead.org>, timvp@...gle.com,
 rafael@...nel.org, pavel@...nel.org, tj@...nel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 lujialin4@...wei.com, chenridong@...wei.com
Subject: Re: [PATCH next] sched,freezer: prevent tasks from escaping being
 frozen



On 2025/7/10 23:44, Michal Koutný wrote:
> On Mon, Jul 07, 2025 at 12:02:47PM +0800, Chen Ridong <chenridong@...weicloud.com> wrote:
>> I was looking at the WARN_ON_ONCE(freezing(p)) check in __thaw_task and started wondering: since we
>> already have !frozen(p) check, is this warning still needed? If we can remove it, maybe reverting
>> commit cff5f49d433f ("cgroup_freezer: cgroup_freezing: Check if not frozen") would be a better approach.
> 
> I think freezing(p) (the part of global freezer) and cgroup_freezing(p)
> should be consistent with each other. AFAICS, the former predicate is
> derived from pm_freezing and that is set all the time between
> freeze_processes() and thaw_processes(), i.e. it stands for both the
> transition (freezing) and goal (frozen).
> With that, the warning in __thaw_task() is incorrect and the solution
> might be the revert + drop the warning.
> 

I'd suggest reverting the commit and dropping the warning. What are your thoughts on this, Peter?

Best regards,
Ridong