linux-kernel - Re: [PATCH 5/5] sched/deadline: Use return value of SCHED_WARN

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Message-ID: <20190729165434.GO31398@hirez.programming.kicks-ass.net>
Date:   Mon, 29 Jul 2019 18:54:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     luca abeni <luca.abeni@...tannapisa.it>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <Valentin.Schneider@....com>,
        Qais Yousef <Qais.Yousef@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] sched/deadline: Use return value of SCHED_WARN_ON()
 in bw accounting

On Fri, Jul 26, 2019 at 12:18:19PM +0200, luca abeni wrote:
> Hi Dietmar,
> 
> On Fri, 26 Jul 2019 09:27:56 +0100
> Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> 
> > To make the decision whether to set rq or running bw to 0 in underflow
> > case use the return value of SCHED_WARN_ON() rather than an extra if
> > condition.
> 
> I think I tried this at some point, but if I remember well this
> solution does not work correctly when SCHED_DEBUG is not enabled.

Well, it 'works' in so far that it compiles. But it might not be what
one expects. That is, for !SCHED_DEBUG the return value is an
unconditional false.

In this case I think that's fine, the WARN _should_ not be happending.