linux-kernel - Re: [PATCH] cgroup/cpuset: Fix "suspicious RCU usage" lockdep warning

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Message-ID: <Yfv9gBps4FU7QgLz@slm.duckdns.org>
Date:   Thu, 3 Feb 2022 06:06:24 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH] cgroup/cpuset: Fix "suspicious RCU usage" lockdep warning

On Wed, Feb 02, 2022 at 10:31:03PM -0500, Waiman Long wrote:
> It was found that a "suspicious RCU usage" lockdep warning was issued
> with the rcu_read_lock() call in update_sibling_cpumasks().  It is
> because the update_cpumasks_hier() function may sleep. So we have
> to release the RCU lock, call update_cpumasks_hier() and reacquire
> it afterward.
> 
> Also add a percpu_rwsem_assert_held() in update_sibling_cpumasks()
> instead of stating that in the comment.
> 
> Fixes: 4716909cc5c5 ("cpuset: Track cpusets that use parent's effective_cpus")
> Signed-off-by: Waiman Long <longman@...hat.com>

Applied to cgroup/for-5.17-fixes.

Thanks.

-- 
tejun