[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <tip-6a503c3be937d275113b702e0421e5b0720abe8a@git.kernel.org>
Date: Fri, 9 Jan 2015 04:33:43 -0800
From: tip-bot for Luca Abeni <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: hpa@...or.com, mingo@...nel.org, torvalds@...ux-foundation.org,
peterz@...radead.org, tglx@...utronix.de, luca.abeni@...tn.it,
linux-kernel@...r.kernel.org, juri.lelli@...il.com,
raistlin@...ux.it, stable@...r.kernel.org
Subject: [tip:sched/urgent] sched/deadline:
Fix migration of SCHED_DEADLINE tasks
Commit-ID: 6a503c3be937d275113b702e0421e5b0720abe8a
Gitweb: http://git.kernel.org/tip/6a503c3be937d275113b702e0421e5b0720abe8a
Author: Luca Abeni <luca.abeni@...tn.it>
AuthorDate: Wed, 17 Dec 2014 11:50:31 +0100
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 9 Jan 2015 11:18:56 +0100
sched/deadline: Fix migration of SCHED_DEADLINE tasks
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@...tn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Juri Lelli <juri.lelli@...il.com>
Cc: <stable@...r.kernel.org>
Cc: Dario Faggioli <raistlin@...ux.it>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/1418813432-20797-2-git-send-email-luca.abeni@unitn.it
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
kernel/sched/deadline.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e5db8c6..55af498 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -826,10 +826,10 @@ 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);
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists