linux-kernel - Re: [PATCH v1 -next 2/3] cgroup/freezer: Reduce redundant propagation for cgroup_propagate

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Message-ID: <x7bbfxw4bq4bjzz5q2viqsf6ogczzbmws5kdudqqcditjbpjln@y35o6uumvhc6>
Date: Tue, 10 Sep 2024 13:33:03 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: Chen Ridong <chenridong@...wei.com>, tj@...nel.org, 
	lizefan.x@...edance.com, hannes@...xchg.org, longman@...hat.com, adityakali@...gle.com, 
	sergeh@...nel.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 -next 2/3] cgroup/freezer: Reduce redundant
 propagation for cgroup_propagate_frozen

On Tue, Sep 10, 2024 at 11:08:12AM GMT, Chen Ridong <chenridong@...weicloud.com> wrote:
> > This should be correct also wrt cgroup creation and removal.
> > 
> Before calling cgroup_freeze, cgroup_freeze_write have hold the
> cgroup_mutex, could parent's nr_frozen_descendants be changed?

Sorry for ambigious wording, I meant that the code you posted appears
to me to be correct (and safe) wrt cgroup tree operations -- thanks to
css_set_lock because frozen bookkeeping is under it (cgroup_mutex would
be too heavy weight for all possible callers of
cgroup_propagate_frozen(), namely cgroup_enter_frozen).

Or do you suggest the current form would need cgroup_mutex
synchronization somehow?

Michal

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