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

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Message-ID: <1524365960.5868.1622643316351.JavaMail.zimbra@efficios.com>
Date:   Wed, 2 Jun 2021 10:15:16 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
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>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        acme <acme@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        paulmck <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        "Joel Fernandes, Google" <joel@...lfernandes.org>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-block@...r.kernel.org, netdev <netdev@...r.kernel.org>,
        linux-usb@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        cgroups <cgroups@...r.kernel.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        linux-perf-users@...r.kernel.org, linux-pm@...r.kernel.org,
        rcu <rcu@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/6] sched,perf,kvm: Fix preemption condition

----- 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.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com