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

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Message-ID: <20170327083508.yjirmwch5jjpforz@hirez.programming.kicks-ass.net>
Date:   Mon, 27 Mar 2017 10:35:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     luca abeni <luca.abeni@...tannapisa.it>,
        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, Mar 24, 2017 at 10:38:31PM -0400, Steven Rostedt wrote:

> > > > @@ -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)..  

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

Two parts;

 1) I prefer braces over any multi line block, irrespective if its a
 single statement or not. This is, afaik, not strictly documented in
 coding style.

 Rationale is that missing braces are bad, and the larger the single
 statement, the harder it is to be sure it is in fact a single
 statement.


 2) If one leg needs braces, then both should get it. This is in fact
 part of CodingStyle.