linux-kernel - Re: [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol

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Message-ID: <779eddcc937941e65659a11b1867c6623a2c8890.camel@redhat.com>
Date:   Tue, 17 Sep 2019 09:06:34 -0500
From:   Scott Wood <swood@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>
Subject: Re: [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep

On Tue, 2019-09-17 at 09:59 +0200, Sebastian Andrzej Siewior wrote:
> On 2019-09-11 17:57:27 [+0100], Scott Wood wrote:
> > diff --git a/kernel/cpu.c b/kernel/cpu.c
> > index 885a195dfbe0..32c6175b63b6 100644
> > --- a/kernel/cpu.c
> > +++ b/kernel/cpu.c
> > @@ -308,7 +308,9 @@ void pin_current_cpu(void)
> >  	preempt_lazy_enable();
> >  	preempt_enable();
> >  
> > +	rt_invol_sleep_inc();
> >  	__read_rt_lock(cpuhp_pin);
> > +	rt_invol_sleep_dec();
> >  
> >  	preempt_disable();
> >  	preempt_lazy_disable();
> 
> I understand the other one. But now looking at it, both end up in
> rt_spin_lock_slowlock_locked() which would be the proper place to do
> that annotation. Okay.

FWIW, if my lazy migrate patchset is accepted, then there will be no users
of __read_rt_lock() outside rwlock-rt.c and it'll be moot.

-Scott