Re: [PATCH 2/2] sched/deadline: Don't return invalid cpu in cpudl_maximum_cpu()

[Byungchul Park]

On Wed, Jun 07, 2017 at 08:42:24AM +0900, Byungchul Park wrote:
> On Tue, Jun 06, 2017 at 04:12:25PM +0100, Juri Lelli wrote:
> > Hi,
> > 
> > On 02/06/17 16:31, Byungchul Park wrote:
> > > When the heap tree is empty, cp->elements[0].cpu has meaningless value.
> 
> Hi,
> 
> The meaningless value is 0.
> 
> > > We need to consider the case.
> > > 
> > > Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
> > > ---
> > >  kernel/sched/cpudeadline.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > > index d4a6963..9b314a9 100644
> > > --- a/kernel/sched/cpudeadline.c
> > > +++ b/kernel/sched/cpudeadline.c
> > > @@ -110,7 +110,8 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
> > >  
> > >  static inline int cpudl_maximum_cpu(struct cpudl *cp)
> > >  {
> > > -	return cp->elements[0].cpu;
> > > +	int cpu = cp->elements[0].cpu;
> > > +	return cp->elements[cpu].idx == IDX_INVALID ? -1 : cpu;
> > 
> > Mmm, don't we get a WARN from cpumask_check() if we return -1 here?
> 
> The function does not return -1 without my patch.
> 
> Right?

Or the following patch would be needed, instead.

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