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| author | Luca Abeni <luca.abeni@unitn.it> | 2014-12-17 11:50:31 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-01-09 11:18:56 +0100 |
| commit | 6a503c3be937d275113b702e0421e5b0720abe8a (patch) | |
| tree | 93c1f7fdef2601a83ab592e458dc4e19a303ec76 | |
| parent | 32a8df4e0b33fccc9715213b382160415b5c4008 (diff) | |
| download | lwn-6a503c3be937d275113b702e0421e5b0720abe8a.tar.gz lwn-6a503c3be937d275113b702e0421e5b0720abe8a.zip | |
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@unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@gmail.com>
Cc: <stable@vger.kernel.org>
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>
| -rw-r--r-- | kernel/sched/deadline.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index e5db8c6feebd..55af498d3c8c 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); } |