linux-kernel - Re: [PATCH 1/2] sched/uclamp: Fix initialization of strut uclamp

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Message-ID: <20200619181303.GD576888@hirez.programming.kicks-ass.net>
Date:   Fri, 19 Jun 2020 20:13:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qais Yousef <qais.yousef@....com>
Cc:     Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Patrick Bellasi <patrick.bellasi@...bug.net>,
        Chris Redpath <chrid.redpath@....com>,
        Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched/uclamp: Fix initialization of strut uclamp_rq

On Fri, Jun 19, 2020 at 06:39:44PM +0100, Qais Yousef wrote:
> On 06/19/20 19:30, Peter Zijlstra wrote:
> > On Thu, Jun 18, 2020 at 08:55:24PM +0100, Qais Yousef wrote:
> > 
> > > +	for_each_clamp_id(clamp_id) {
> > > +		memset(uc_rq[clamp_id].bucket,
> > > +		       0,
> > > +		       sizeof(struct uclamp_bucket)*UCLAMP_BUCKETS);
> > > +
> > > +		uc_rq[clamp_id].value = uclamp_none(clamp_id);
> > 
> > I think you can replace all that with:
> > 
> > 		*uc_rq = (struct uclamp_rq){
> > 			.value = uclamp_none(clamp_id),
> > 		};
> > 
> > it's shorter and is free or weird line-breaks :-)
> 
> Sure. I just sent v2 so that people will be encouraged to run tests hopefully.
> But will fix in v3.
> 
> Do we actually need to 0 out anything here? Shouldn't the runqueues all be in
> BSS which gets initialized to 0 by default at boot?
> 
> Maybe better stay explicit..

C99 named initializer (as used here) explicitly zero initializes all
unnamed members. Is that explicit enough? ;-)