[PATCH 3/5] sched/deadline: Fix wrong cpudl_find() in check_preempt_equal_dl()

Xunlei Pang
2015-01-19T04:54:02Z

In check_preempt_equal_dl(), cpudl_find() is called with a NULL
later_mask, thus cpudl_find() here doesn't check cpudl::free_cpus
at all.

This patch takles this issue by always passing a non-NULL later_mask
to cpudl_find(), thereby fixing this issue.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
kernel/sched/cpudeadline.c | 8 +++-----
kernel/sched/deadline.c | 15 +++++++++++----
2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index c6acb07..f331fcf 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -97,7 +97,7 @@ static inline int cpudl_maximum(struct cpudl *cp)
* cpudl_find - find the best (later-dl) CPU in the system
* @cp: the cpudl max-heap context
* @p: the task
- * @later_mask: a mask to fill in with the selected CPUs (or NULL)
+ * @later_mask: a mask to fill in with the selected CPUs (not NULL)
*
* Returns: int - best CPU (heap maximum if suitable)
*/
@@ -107,15 +107,13 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
int best_cpu = -1;
const struct sched_dl_entity *dl_se = &p->dl;

- if (later_mask &&
- cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
+ if (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);
- if (later_mask)
- cpumask_set_cpu(best_cpu, later_mask);
+ cpumask_set_cpu(best_cpu, later_mask);
}

out:
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e7b2722..82d900f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -943,14 +943,23 @@ out:
return cpu;
}

+static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
+
static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
{
+ struct cpumask *later_mask =
+ this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
+
+ /* Make sure the mask is initialized first */
+ if (unlikely(!later_mask))
+ return;
+
/*
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
if (rq->curr->nr_cpus_allowed == 1 ||
- cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
+ cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == -1)
return;

/*
@@ -958,7 +967,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
* see if it is pushed or pulled somewhere else.
*/
if (p->nr_cpus_allowed != 1 &&
- cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
+ cpudl_find(&rq->rd->cpudl, p, later_mask) != -1)
return;

resched_curr(rq);
@@ -1145,8 +1154,6 @@ next_node:
return NULL;
}

-static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
-
static int find_later_rq(struct task_struct *task)
{
struct sched_domain *sd;
--
1.9.1