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Date: Tue, 12 May 2026 18:49:47 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Michael Wu <michael@allwinnertech.com>,
	Xiaosen He <xiaosen.he@oss.qualcomm.com>, Tejun Heo <tj@kernel.org>,
	Thomas Gleixner <tglx@kernel.org>
Subject: Re: [PATCH] sched: flush plug in schedule_preempt_disabled() to
 prevent deadlock
Message-ID: <20260512164947.GA2677887@noisy.programming.kicks-ass.net>
References: <20260512085939.1107372-1-tom.leiming@gmail.com>
 <20260512120431.GC1889694@noisy.programming.kicks-ass.net>
 <20260512124021.GA2214256@noisy.programming.kicks-ass.net>
 <agNLCof3zO5-QAo9@fedora>
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In-Reply-To: <agNLCof3zO5-QAo9@fedora>

On Tue, May 12, 2026 at 11:45:14PM +0800, Ming Lei wrote:

> > io_schedule()
> >   token = io_schedule_prepare()
> >     blk_flush_plug(current->plug, true);
> >   schedule()
> >     if (!task_is_running(tsk))
> >       sched_submit_work()
> >         blk_flush_plug(tsk->plug, true);
> > 
> > Why isn't the one in sched_submit_work() sufficient? This thing either
> > needs a comment justifying its existence, or get removed.

> If io_schedule_prepare() can be called in every iowait context, looks
> blk_flush_plug() from sched_submit_work() may be removed.

No, the other way around. I don't see the point of having the one in
io_schedule_prepare(), since we'll hit the one in sched_submit_work().