linux-kernel - Re: [PATCH v2] sched/core: Preempt current task in favour of bound kthread

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Date:   Tue, 10 Dec 2019 10:33:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Dave Chinner <david@...morbit.com>, Phil Auld <pauld@...hat.com>,
        Ming Lei <ming.lei@...hat.com>, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jeff Moyer <jmoyer@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        Eric Sandeen <sandeen@...hat.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH v2] sched/core: Preempt current task in favour of bound
 kthread

On Tue, Dec 10, 2019 at 10:26:01AM +0100, Peter Zijlstra wrote:

> > @@ -6716,7 +6737,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
> >  	find_matching_se(&se, &pse);
> >  	update_curr(cfs_rq_of(se));
> >  	BUG_ON(!pse);
> > -	if (wakeup_preempt_entity(se, pse) == 1) {
> > +	if (wakeup_preempt_entity(se, pse) == 1 || kthread_wakeup_preempt(rq, p, wake_flags)) {
> >  		/*
> >  		 * Bias pick_next to pick the sched entity that is
> >  		 * triggering this preemption.
> 
> How about something like:
> 
	if (wakeup_preempt_entity(se, pse) >= !(wake_flags & WF_KTHREAD))

That's a slightly less convoluted expression for the same value :-)