linux-kernel - Re: [PATCH v2 1/1] cgroup: replace global percpu_rwsem with signal_struct->group

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Message-ID: <aLpdc4oDdAxvtUQT@slm.duckdns.org>
Date: Thu, 4 Sep 2025 17:48:03 -1000
From: Tejun Heo <tj@...nel.org>
To: escape <escape@...ux.alibaba.com>
Cc: hannes@...xchg.org, mkoutny@...e.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] cgroup: replace global percpu_rwsem with
 signal_struct->group_rwsem when writing cgroup.procs/threads

Hello,

On Fri, Sep 05, 2025 at 11:44:53AM +0800, escape wrote:
...
> To avoid the complexity of runtime changes to favordynmods, perhaps a
> better approach would be to introduce a separate control variable,
> configured via a kernel command line parameter such as
> cgroup_migration_lock=[global|thread_group] to explicitly govern this
> behavior. What do you think about this approach?

Can't you just down_write threadgroup_rwsem when flipping the flag? Wouldn't
that provide sufficient synchronization?

Thanks.

-- 
tejun