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authorLuca Abeni <luca.abeni@unitn.it>2014-12-17 11:50:31 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-16 06:59:33 -0800
commit678c8bb7aa75fb956b311b42ad4b7262bcc24b5e (patch)
tree25fd5e2ccc877bc223da88bc84c062ef5ed28e02
parent11d1b5db26bdb35063850dfb662b2e7de159a4be (diff)
downloadlinux-linaro-stable-678c8bb7aa75fb956b311b42ad4b7262bcc24b5e.tar.gz
sched/deadline: Fix migration of SCHED_DEADLINE tasks
commit 6a503c3be937d275113b702e0421e5b0720abe8a upstream. According to global EDF, tasks should be migrated between runqueues without checking if their scheduling deadlines and runtimes are valid. However, SCHED_DEADLINE currently performs such a check: a migration happens doing: deactivate_task(rq, next_task, 0); set_task_cpu(next_task, later_rq->cpu); activate_task(later_rq, next_task, 0); which ends up calling dequeue_task_dl(), setting the new CPU, and then calling enqueue_task_dl(). enqueue_task_dl() then calls enqueue_dl_entity(), which calls update_dl_entity(), which can modify scheduling deadline and runtime, breaking global EDF scheduling. As a result, some of the properties of global EDF are not respected: for example, a taskset {(30, 80), (40, 80), (120, 170)} scheduled on two cores can have unbounded response times for the third task even if 30/80+40/80+120/170 = 1.5809 < 2 This can be fixed by invoking update_dl_entity() only in case of wakeup, or if this is a new SCHED_DEADLINE task. Signed-off-by: Luca Abeni <luca.abeni@unitn.it> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juri Lelli <juri.lelli@gmail.com> Cc: Dario Faggioli <raistlin@linux.it> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1418813432-20797-2-git-send-email-luca.abeni@unitn.it Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/sched/deadline.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 37dac98c0749..b3228b9647f0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -806,10 +806,10 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
* parameters of the task might need updating. Otherwise,
* we want a replenishment of its runtime.
*/
- if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
- replenish_dl_entity(dl_se, pi_se);
- else
+ if (dl_se->dl_new || flags & ENQUEUE_WAKEUP)
update_dl_entity(dl_se, pi_se);
+ else if (flags & ENQUEUE_REPLENISH)
+ replenish_dl_entity(dl_se, pi_se);
__enqueue_dl_entity(dl_se);
}