[3.16.y-ckt stable] Patch "sched/deadline: Fix migration of SCHED_DEADLINE tasks" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Mon Jan 19 13:36:14 UTC 2015
This is a note to let you know that I have just added a patch titled
sched/deadline: Fix migration of SCHED_DEADLINE tasks
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt5.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 225a4eaaeccc4c197f76ab98699eb8f023c611f2 Mon Sep 17 00:00:00 2001
From: Luca Abeni <luca.abeni at unitn.it>
Date: Wed, 17 Dec 2014 11:50:31 +0100
Subject: 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 at unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Acked-by: Juri Lelli <juri.lelli at gmail.com>
Cc: Dario Faggioli <raistlin at linux.it>
Cc: Linus Torvalds <torvalds at 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 at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
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 fc4f98b1258f..a07b08ce8307 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -823,10 +823,10 @@ 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);
}
--
2.1.4
More information about the kernel-team
mailing list