linux-kernel - Re: [PATCH] cpuset: relax locking on cpuset_node

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Message-ID: <CAGj-7pXC0fDLWsuUh7PLNSyzCv-4LqKoOfE=hizUeOfoJqQ7Ag@mail.gmail.com>
Date: Mon, 21 Apr 2025 21:41:13 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Gregory Price <gourry@...rry.net>
Cc: linux-mm@...ck.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	kernel-team@...a.com, longman@...hat.com, hannes@...xchg.org, 
	mhocko@...nel.org, roman.gushchin@...ux.dev, muchun.song@...ux.dev, 
	tj@...nel.org, mkoutny@...e.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] cpuset: relax locking on cpuset_node_allowed

On Mon, Apr 21, 2025 at 9:30 PM Gregory Price <gourry@...rry.net> wrote:
>
> The cgroup_get_e_css reference protects the css->effective_mems, and
> calls of this interface would be subject to the same race conditions
> associated with a non-atomic access to cs->effective_mems.
>
> So while this interface cannot make strong guarantees of correctness,
> it can therefore avoid taking a global or rcu_read_lock for performance.
>
> Drop the rcu_read_lock from cpuset_node_allowed.
>
> Suggested-by: Shakeel Butt <shakeel.butt@...ux.dev>
> Suggested-by: Waiman Long <longman@...hat.com>
> Signed-off-by: Gregory Price <gourry@...rry.net>

Reviewed-by: Shakeel Butt <shakeel.butt@...ux.dev>