From: Frederic Weisbecker <frederic@kernel.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
urezki@gmail.com, neeraj.iitr10@gmail.com, paulmck@kernel.org,
rostedt@goodmis.org
Subject: Re: [RFC] rcu/nocb: Fix possible bugs in rcu_barrier()
Date: Mon, 19 Sep 2022 11:34:11 +0200 [thread overview]
Message-ID: <20220919093411.GB56640@lothringen> (raw)
In-Reply-To: <20220918221231.79143-1-joel@joelfernandes.org>
On Sun, Sep 18, 2022 at 10:12:31PM +0000, Joel Fernandes (Google) wrote:
> When going through the lazy-rcu work, I noticed that
> rcu_barrier_entrain() does not really wake up the rcuog GP thread in any
> path after entraining. This means it is possible the GP thread is not
> awakened soon (say there were no CBs in the cblist after entraining
> time).
Right.
>
> Further, nothing appears to be calling the rcu_barrier callback
> directly in the case the ->cblist was empty which means if the IPI gets
> delayed enough to make the ->cblist empty and it turns out to be the last
> CPU holding, then nothing calls completes rcu_state.barrier_completion.
No need for that, if the cblist is empty there is no need for a callback
to enqueue.
Thanks.
next prev parent reply other threads:[~2022-09-19 9:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-18 22:12 Joel Fernandes (Google)
2022-09-18 22:17 ` Joel Fernandes
2022-09-19 9:34 ` Frederic Weisbecker [this message]
2022-09-19 21:00 ` Joel Fernandes
2022-09-21 7:49 ` [rcu/nocb] 79b696b5c3: WARNING:at_kernel/rcu/tree_nocb.h:#rcu_barrier_entrain kernel test robot
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