linux-kernel - Re: [PATCH v2 2/7] sched: Introduce task_is

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Message-ID: <YMMpPmDh+7kTecgg@hirez.programming.kicks-ass.net>
Date:   Fri, 11 Jun 2021 11:13:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.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>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Jens Axboe <axboe@...nel.dk>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...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>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
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        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>,
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        Joel Fernandes <joel@...lfernandes.org>,
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        Stephen Boyd <sboyd@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v2 2/7] sched: Introduce task_is_running()

On Fri, Jun 11, 2021 at 10:49:56AM +0200, Geert Uytterhoeven wrote:
> Hoi Peter,
> 
> Thanks for your patch!
> 
> On Fri, Jun 11, 2021 at 10:36 AM Peter Zijlstra <peterz@...radead.org> wrote:
> > Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
> > task_is_running(p).
> 
> You're also sticking a READ_ONCE() in the helper, which wasn't done
> by any of the old implementations? Care to mention why?

Patch 7/7 should clarify. Arguably I should leave the READ_ONCE() off
here and only add it there.