On 09/06/17 11:43, Byungchul Park wrote:
> On Thu, Jun 08, 2017 at 03:02:43PM +0100, Juri Lelli wrote:
> > On 07/06/17 09:14, Byungchul Park wrote:
> > > 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:
> >
> > [...]
> >
> > > > > >
> > > > > > 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?
> > >
> >
> > That's actually my point: with the change you are proposing we will
> > start returning -1 and it looks to me that the WARN will start to fire.
>
> Hi,
>
> I see what you talk about. You are talking about WARN in cpumask_check().
> Sorry for missing your words.
>
> > What about the below instead (properly splitted in 2 patches I guess,
> > and I'm not sure at all the macro thing is pretty at all) ?
> >
> > --->8---
> > kernel/sched/cpudeadline.c | 19 +++++++++++++------
> > 1 file changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > index fba235c7d026..32e3dcef2b81 100644
> > --- a/kernel/sched/cpudeadline.c
> > +++ b/kernel/sched/cpudeadline.c
> > @@ -108,11 +108,17 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
> > cpudl_heapify_down(cp, idx);
> > }
> >
> > -static inline int cpudl_maximum(struct cpudl *cp)
> > -{
> > - return cp->elements[0].cpu;
> > +#define cpudl_maximum(field) \
> > +static inline int cpudl_maximum_##field \
> > +(struct cpudl *cp) \
> > +{ \
> > + return cp->elements[0].field; \
> > }
> >
> > +cpudl_maximum(cpu);
> > +cpudl_maximum(dl);
> > +cpudl_maximum(idx);
> > +
> > /*
> > * cpudl_find - find the best (later-dl) CPU in the system
> > * @cp: the cpudl max-heap context
> > @@ -131,9 +137,10 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> > cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
> > best_cpu = cpumask_any(later_mask);
> > goto out;
> > - } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
> > - dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
> > - best_cpu = cpudl_maximum(cp);
> > + } else if (cpudl_maximum_idx(cp) != IDX_INVALID &&
> > + cpumask_test_cpu(cpudl_maximum_cpu(cp), &p->cpus_allowed) &&
> > + dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> > + best_cpu = cpudl_maximum_cpu(cp);
>
> This would also work and avoid unnecessary warning. I missed the check
> to avoid it. https://lkml.org/lkml/2017/3/23/175 was an original patch
> doing it.
>
> By the way, frankly speaking, I don't like accessing the cpudl instant
> several times without protection. I rather prefer the following..
>
> But whatever. I like both.
>
> Thnaks,
> Byungchul
>
> ----->8-----
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 9b314a9..1d369cf 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -137,11 +137,17 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
> best_cpu = cpumask_any(later_mask);
> goto out;
> - } else if (cpumask_test_cpu(cpudl_maximum_cpu(cp), &p->cpus_allowed) &&
> - dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> - best_cpu = cpudl_maximum_cpu(cp);
> - if (later_mask)
> - cpumask_set_cpu(best_cpu, later_mask);
> + } else {
> + int max_cpu = cpudl_maximum_cpu(cp);
> + u64 max_dl = cpudl_maximum_dl(cp);
> +
> + if (max_cpu != -1 &&
> + cpumask_test_cpu(max_cpu, &p->cpus_allowed) &&
> + dl_time_before(dl_se->deadline, max_dl)) {
Don't we access cp 3 times both ways?
