linux-kernel - Re: [RFC v5 5/9] sched/deadline: do not reclaim the whole CPU bandwidth

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Date:   Fri, 24 Mar 2017 22:38:31 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     luca abeni <luca.abeni@...tannapisa.it>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [RFC v5 5/9] sched/deadline: do not reclaim the whole CPU
 bandwidth

On Fri, 24 Mar 2017 22:58:27 +0100
luca abeni <luca.abeni@...tannapisa.it> wrote:

> Hi Peter,
> 
> On Fri, 24 Mar 2017 15:00:15 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Fri, Mar 24, 2017 at 04:52:58AM +0100, luca abeni wrote:
> >   
> > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > index 20c62e7..efa88eb 100644
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -6716,6 +6716,12 @@ static void sched_dl_do_global(void)
> > >  		raw_spin_unlock_irqrestore(&dl_b->lock, flags);
> > >  
> > >  		rcu_read_unlock_sched();
> > > +		if (dl_b->bw == -1)
> > > +			cpu_rq(cpu)->dl.deadline_bw_inv = 1 << 8;
> > > +		else
> > > +			cpu_rq(cpu)->dl.deadline_bw_inv =
> > > +				to_ratio(global_rt_runtime(),
> > > +					 global_rt_period()) >>
> > > 12;    
> > 
> > Coding style requires braces here (on both legs of the condition)..  
> 
> Sorry about this; checkpatch did not complain and I did not check the
> coding rules. I'll add the braces.

I'm not sure it's completely documented anywhere.

The brackets are not needed if there's one statement after the if, but
for readability, it's sometimes best to put brackets in if there's more
than one line. That can even include comments. It's not a hard rule,
but more of a preference. I'm personally OK with the above, but Peter
being the maintainer, has the say to give the preference of this kind
of rule.

-- Steve