linux-kernel - Re: [PATCH 3/6] sched: Extract __schedule

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Message-ID: <20230815224233.GD602899@lorien.usersys.redhat.com>
Date:   Tue, 15 Aug 2023 18:42:33 -0400
From:   Phil Auld <pauld@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     bigeasy@...utronix.de, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, bsegall@...gle.com,
        boqun.feng@...il.com, swood@...hat.com, bristot@...hat.com,
        dietmar.eggemann@....com, mingo@...hat.com, jstultz@...gle.com,
        juri.lelli@...hat.com, mgorman@...e.de, rostedt@...dmis.org,
        vschneid@...hat.com, vincent.guittot@...aro.org,
        longman@...hat.com, will@...nel.org
Subject: Re: [PATCH 3/6] sched: Extract __schedule_loop()

On Tue, Aug 15, 2023 at 06:33:01PM -0400 Phil Auld wrote:
> Hi Peter,
> 
> On Tue, Aug 15, 2023 at 01:01:24PM +0200 Peter Zijlstra wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > There are currently two implementations of this basic __schedule()
> > loop, and there is soon to be a third.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Link: https://lkml.kernel.org/r/20230427111937.2745231-2-bigeasy@linutronix.de
> > ---
> >  kernel/sched/core.c |   21 +++++++++++----------
> >  1 file changed, 11 insertions(+), 10 deletions(-)
> > 
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -6787,16 +6787,21 @@ static void sched_update_worker(struct t
> >  	}
> >  }
> >  
> > -asmlinkage __visible void __sched schedule(void)
> > +static __always_inline void __schedule_loop(unsigned int sched_mode)
> 
> I think this needs __sched or it's the only thing that ever shows up
> in wchan. E.g.
>

Using this command:

    ps -Ao pid,f,fname,s,wchan 


>   16995 0 bash     S __schedule_loop.constprop.0
>   17036 1 kworker/ I __schedule_loop.constprop.0
>   17151 1 kworker/ I __schedule_loop.constprop.0
>   17235 0 sleep    S __schedule_loop.constprop.0
>   17236 4 ps       R -
> 
> vs
> 
>   10417 1 kworker/ I worker_thread
>   10665 1 kworker/ I worker_thread
>   10670 4 sshd     D -            
>   10674 4 bash     S do_wait      
>   10701 0 sleep    S hrtimer_nanosleep
>   10702 4 ps       R -
> 
> Otherwise, looking forward to getting this and the rest of RT in...
> 
> Cheers,
> Phil
> 
> >  {
> > -	struct task_struct *tsk = current;
> > -
> > -	sched_submit_work(tsk);
> >  	do {
> >  		preempt_disable();
> > -		__schedule(SM_NONE);
> > +		__schedule(sched_mode);
> >  		sched_preempt_enable_no_resched();
> >  	} while (need_resched());
> > +}
> > +
> > +asmlinkage __visible void __sched schedule(void)
> > +{
> > +	struct task_struct *tsk = current;
> > +
> > +	sched_submit_work(tsk);
> > +	__schedule_loop(SM_NONE);
> >  	sched_update_worker(tsk);
> >  }
> >  EXPORT_SYMBOL(schedule);
> > @@ -6860,11 +6865,7 @@ void __sched schedule_preempt_disabled(v
> >  #ifdef CONFIG_PREEMPT_RT
> >  void __sched notrace schedule_rtlock(void)
> >  {
> > -	do {
> > -		preempt_disable();
> > -		__schedule(SM_RTLOCK_WAIT);
> > -		sched_preempt_enable_no_resched();
> > -	} while (need_resched());
> > +	__schedule_loop(SM_RTLOCK_WAIT);
> >  }
> >  NOKPROBE_SYMBOL(schedule_rtlock);
> >  #endif
> > 
> > 
> 
> -- 
> 

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