linux-kernel - Re: [PATCH 2/2] cgroup/cpuset: Change callback_lock to raw_spinlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aPZqk4h0ek_QM9o5@slm.duckdns.org>
Date: Mon, 20 Oct 2025 07:00:03 -1000
From: Tejun Heo <tj@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Chen Ridong <chenridong@...wei.com>
Subject: Re: [PATCH 2/2] cgroup/cpuset: Change callback_lock to raw_spinlock_t

On Sun, Oct 19, 2025 at 10:32:07PM -0400, Waiman Long wrote:
> The callback_lock is acquired either to read a stable set of cpu
> or node masks or to modify those masks when cpuset_mutex is also
> acquired. Sometime, it may need to go up the cgroup hierarchy while
> holding the lock to find the right set of masks to use. Assuming that
> the depth of the cgroup hierarch is finite and typically small, the
> lock hold time should be limited.
> 
> As a result, it can be converted to raw_spinlock_t to reduce overhead
> in a PREEMPT_RT setting without introducing excessive latency.
> 
> Signed-off-by: Waiman Long <longman@...hat.com>

Is this something that RT people would like? Why does the overhead of the
lock matter? I think this patch requires more justifications.

Thanks.

-- 
tejun