netdev - Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition

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Message-ID: <YLeUfNEqKg27VwAB@hirez.programming.kicks-ass.net>
Date:   Wed, 2 Jun 2021 16:23:56 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>, bristot <bristot@...hat.com>,
        Borislav Petkov <bp@...en8.de>, x86 <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Jens Axboe <axboe@...nel.dk>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
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        kgdb-bugreport@...ts.sourceforge.net,
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        KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition

On Wed, Jun 02, 2021 at 10:15:16AM -0400, Mathieu Desnoyers wrote:
> ----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra peterz@...radead.org wrote:
> [...]
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -8568,13 +8568,12 @@ static void perf_event_switch(struct tas
> > 		},
> > 	};
> > 
> > -	if (!sched_in && task->state == TASK_RUNNING)
> > +	if (!sched_in && current->on_rq) {
> > 		switch_event.event_id.header.misc |=
> > 				PERF_RECORD_MISC_SWITCH_OUT_PREEMPT;
> > +	}
> > 
> > -	perf_iterate_sb(perf_event_switch_output,
> > -		       &switch_event,
> > -		       NULL);
> > +	perf_iterate_sb(perf_event_switch_output, &switch_event, NULL);
> > }
> 
> There is a lot of code cleanup going on here which does not seem to belong
> to a "Fix" patch.

Maybe, but I so hate whitespace only patches :-/