linux-kernel - Re: [PATCH] cgroup: Fix incorrect WARN_ON_ONCE() in css_release_work

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Message-ID: <ZrZFhe-teNE6xAKn@slm.duckdns.org>
Date: Fri, 9 Aug 2024 06:36:21 -1000
From: Tejun Heo <tj@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Kamalesh Babulal <kamalesh.babulal@...cle.com>
Subject: Re: [PATCH] cgroup: Fix incorrect WARN_ON_ONCE() in
 css_release_work_fn()

On Thu, Aug 08, 2024 at 11:22:59PM -0400, Waiman Long wrote:
> It turns out that the WARN_ON_ONCE() call in css_release_work_fn
> introduced by commit ab0312526867 ("cgroup: Show # of subsystem CSSes
> in cgroup.stat") is incorrect. Although css->nr_descendants must be
> 0 when a css is released and ready to be freed, the corresponding
> cgrp->nr_dying_subsys[ss->id] may not be 0 if a subsystem is activated
> and deactivated multiple times with one or more of its previous
> activation leaving behind dying csses.
> 
> Fix the incorrect warning by removing the cgrp->nr_dying_subsys check.
> 
> Fixes: ab0312526867 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
> Closes: https://lore.kernel.org/cgroups/6f301773-2fce-4602-a391-8af7ef00b2fb@redhat.com/T/#t
> Signed-off-by: Waiman Long <longman@...hat.com>

Applied to cgroup/for-6.12.

Thanks.

-- 
tejun