Subject: Re: linux-next: build warning after merge of the tip tree

From: Peter Zijlstra <[email-masked]>
Date: Wed, 6 Oct 2021 08:59:31 +0200

On Wed, Oct 06, 2021 at 02:06:55PM +1100, Stephen Rothwell wrote:
> Hi Peter,
> 
> On Mon, 20 Sep 2021 13:18:53 +0200 Peter Zijlstra <[email-masked]> wrote:
> >
> > On Mon, Sep 20, 2021 at 11:33:30AM +1000, Stephen Rothwell wrote:
> > > 
> > > After merging the tip tree, today's linux-next build (powerpc_ppc64
> > > defconfig) produced this warning:
> > > 
> > > kernel/sched/debug.c: In function 'print_cfs_group_stats':
> > > kernel/sched/debug.c:460:41: warning: unused variable 'stats' [-Wunused-variable]
> > >   460 |                struct sched_statistics *stats =  __schedstats_from_se(se);
> > >       |                                         ^~~~~
> > 
> > So I've not seen that one *yet*, I've dont a bunch of SCHEDSTAT=n
> > builds. I do think GCC is being quite stupid for giving it, seeing how
> > the whole thing is within if (0). The GCC people seem to disagree when I
> > brought it up.
> > 
> > Anyway, what I did in other parts was the below; that seems to 'upgrade'
> > the warnings from -Wunused-variable to -Wunused-but-set-variable, and
> > that latter *is* in W=1, and I'm arguing it should be promoted to W=2 or
> > thereabout.
> > 
> > Given that whole if(0) {} thing, I don't feel motivated to change things
> > overly much and quite strongly feel this is the compiler being daft.
> > 
> > ---
> > 
> > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> > index 935dad7dffb7..ef71de01e4d7 100644
> > --- a/kernel/sched/debug.c
> > +++ b/kernel/sched/debug.c
> > @@ -457,7 +457,8 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
> >  	PN(se->sum_exec_runtime);
> >  
> >  	if (schedstat_enabled()) {
> > -               struct sched_statistics *stats =  __schedstats_from_se(se);
> > +		struct sched_statistics *stats;
> > +		stats = __schedstats_from_se(se);
> >  
> >  		PN_SCHEDSTAT(wait_start);
> >  		PN_SCHEDSTAT(sleep_start);
> 
> Any progress on this?  I am still getting the warning.

Urgh, sorry, fell through cracks. Will commit fixup in a few.