From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH linux-next] cgroup: fix suspicious
 rcu_dereference_check() usage warning
Date: Sat, 12 Mar 2022 13:19:13 +0100
Message-ID: <20220312121913.GA28057@worktop.programming.kicks-ass.net>
References: <20220305034103.57123-1-zhouchengming@bytedance.com>
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To: Chengming Zhou <zhouchengming@bytedance.com>
Cc: tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, songmuchun@bytedance.com, Linux Kernel Functional Testing <lkft@linaro.org>, syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com, Zhouyi Zhou <zhouzhouyi@gmail.com>

On Sat, Mar 05, 2022 at 11:41:03AM +0800, Chengming Zhou wrote:
> task_css_set_check() will use rcu_dereference_check() to check for
> rcu_read_lock_held() on the read-side, which is not true after commit
> dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock"). This
> commit drop explicit rcu_read_lock(), change to RCU-sched read-side
> critical section. So fix the RCU warning by adding check for
> rcu_read_lock_sched_held().
> 
> Fixes: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock")
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Reported-by: syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com
> Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>

Thanks, I'll go stick this in sched/core so it's in the same branch that
caused the problem.