linux-kernel - Re: [PATCH v3 08/14] cgroup: Remove redundant rcu_read_lock/unlock() in spin

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Message-ID: <aMmuTXNPY_9Fp_WQ@slm.duckdns.org>
Date: Tue, 16 Sep 2025 08:37:01 -1000
From: Tejun Heo <tj@...nel.org>
To: pengdonglin <dolinux.peng@...il.com>
Cc: tony.luck@...el.com, jani.nikula@...ux.intel.com, ap420073@...il.com,
	jv@...sburgh.net, freude@...ux.ibm.com, bcrl@...ck.org,
	trondmy@...nel.org, longman@...hat.com, kees@...nel.org,
	bigeasy@...utronix.de, hdanton@...a.com, paulmck@...nel.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	linux-nfs@...r.kernel.org, linux-aio@...ck.org,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
	intel-gfx@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-s390@...r.kernel.org,
	cgroups@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
	pengdonglin <pengdonglin@...omi.com>
Subject: Re: [PATCH v3 08/14] cgroup: Remove redundant rcu_read_lock/unlock()
 in spin_lock

On Tue, Sep 16, 2025 at 12:47:29PM +0800, pengdonglin wrote:
> From: pengdonglin <pengdonglin@...omi.com>
> 
> Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
> there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
> rcu_read_lock_sched() in terms of RCU read section and the relevant grace
> period. That means that spin_lock(), which implies rcu_read_lock_sched(),
> also implies rcu_read_lock().
> 
> There is no need no explicitly start a RCU read section if one has already
> been started implicitly by spin_lock().
> 
> Simplify the code and remove the inner rcu_read_lock() invocation.
> 
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Waiman Long <longman@...hat.com>
> Signed-off-by: pengdonglin <pengdonglin@...omi.com>
> Signed-off-by: pengdonglin <dolinux.peng@...il.com>

Applied to cgroup/for-6.18.

Thanks.

-- 
tejun