linux-kernel - Re: [PATCH] kernel/time/posix-cpu-timers: Remove useless call to check_dl

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Message-ID: <20181107150221.GJ9761@hirez.programming.kicks-ass.net>
Date:   Wed, 7 Nov 2018 16:02:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Juri Lelli <juri.lelli@...hat.com>, mingo@...hat.com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        luca.abeni@...tannapisa.it, claudio@...dence.eu.com,
        bristot@...hat.com, linux-rt-users@...r.kernel.org,
        mtk.manpages@...il.com,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH] kernel/time/posix-cpu-timers: Remove useless call to
 check_dl_overrun

On Wed, Nov 07, 2018 at 09:56:27AM -0500, Steven Rostedt wrote:
> On Wed,  7 Nov 2018 12:10:32 +0100
> Juri Lelli <juri.lelli@...hat.com> wrote:
> 
> > check_dl_overrun is used to send a SIGXCPU to users that asked to be
> > informed when SCHED_DEADLINE runtime overruns occur.
> > 
> > The function is called by check_thread_timers already, so the call in
> > check_process_timers is redundant/wrong (even though harmless).
> > 
> > Remove it.
> > 
> > Fixes: 34be39305a77 ("sched/deadline: Implement "runtime overrun signal" support")
> > Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Luca Abeni <luca.abeni@...tannapisa.it>
> > Cc: Claudio Scordino <claudio@...dence.eu.com>
> > Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> > ---
> >  kernel/time/posix-cpu-timers.c | 3 ---
> >  1 file changed, 3 deletions(-)
> > 
> > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
> > index ce32cf741b25..8f0644af40be 100644
> > --- a/kernel/time/posix-cpu-timers.c
> > +++ b/kernel/time/posix-cpu-timers.c
> > @@ -917,9 +917,6 @@ static void check_process_timers(struct task_struct *tsk,
> >  	struct task_cputime cputime;
> >  	unsigned long soft;
> >  
> > -	if (dl_task(tsk))
> > -		check_dl_overrun(tsk);
> > -
> 
> Hmm, I wonder if we should just move this check directly into
> run_posix_cpu_timers() directly. Why is it hidden in this call?

It is not; it is duplicated in this call. The one in
check_thread_timeres() makes sense (it is a thread property).