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Subject[PATCH 3/3] sched/deadline: fix inter- exclusive cpusets migrations
Date
Users can perform clustered scheduling using the cpuset facility.
After an exclusive cpuset is created, task migrations happen only
between CPUs belonging to the same cpuset. Inter- cpuset migrations
can only happen when the user requires so, moving a task between
different cpusets. This behaviour is broken in SCHED_DEADLINE, as
currently spurious inter- cpuset migration may happen without
user intervention.

This patch fix the problem (and shuffles the code a bit to improve
clarity).

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Fabio Checconi <fchecconi@gmail.com>
Cc: linux-kernel@vger.kernel.org
---
kernel/sched/cpudeadline.c | 4 +---
kernel/sched/deadline.c | 7 +++++++
2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index bd95963..539ca3c 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -107,9 +107,7 @@ 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) && cpumask_and(later_mask,
- later_mask, cpu_active_mask)) {
+ if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) {
best_cpu = cpumask_any(later_mask);
goto out;
} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 56cb157..2799441 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1169,6 +1169,13 @@ static int find_later_rq(struct task_struct *task)
if (task->nr_cpus_allowed == 1)
return -1;

+ /*
+ * We have to consider system topology and task affinity
+ * first, then we can look for a suitable cpu.
+ */
+ cpumask_copy(later_mask, task_rq(task)->rd->span);
+ cpumask_and(later_mask, later_mask, cpu_active_mask);
+ cpumask_and(later_mask, later_mask, &task->cpus_allowed);
best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
task, later_mask);
if (best_cpu == -1)
--
2.1.0



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