On Fri, Jun 09, 2017 at 12:42:06PM +0100, Juri Lelli wrote: > > > > 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?
I wonder if I miss something.. As you said, in most cases it will, but I am not sure if we can guarentee that, regardless of arches or compile optimization level. Sorry if I am wrong.
