linux-kernel - Re: [PATCH v5 2/3] cgroup: relocate cgroup_attach_lock within cgroup_procs_write

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Message-ID: <aMG19vnh_nd_jm_h@slm.duckdns.org>
Date: Wed, 10 Sep 2025 07:31:34 -1000
From: Tejun Heo <tj@...nel.org>
To: Yi Tao <escape@...ux.alibaba.com>
Cc: hannes@...xchg.org, mkoutny@...e.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/3] cgroup: relocate cgroup_attach_lock within
 cgroup_procs_write_start

On Wed, Sep 10, 2025 at 02:59:34PM +0800, Yi Tao wrote:
> Later patches will introduce a new parameter `task` to
> cgroup_attach_lock, thus adjusting the position of cgroup_attach_lock
> within cgroup_procs_write_start.
> 
> Between obtaining the threadgroup leader via PID and acquiring the
> cgroup attach lock, the threadgroup leader may change, which could lead
> to incorrect cgroup migration. Therefore, after acquiring the cgroup
> attach lock, we check whether the threadgroup leader has changed, and if
> so, retry the operation.
> 
> Signed-off-by: Yi Tao <escape@...ux.alibaba.com>

Applied to cgroup/for-6.18 with minor comment adjustments.

Thanks.

-- 
tejun