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

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);
if (later_mask)
cpumask_set_cpu(best_cpu, later_mask);
}
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