Commit fbbd9c2a847c7082e6d532e971e6c6f74f9b57b0
Committed by
Greg Kroah-Hartman
1 parent
8b65e97d82
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>
Showing 1 changed file with 3 additions and 3 deletions Side-by-side Diff
kernel/sched/deadline.c
... | ... | @@ -831,10 +831,10 @@ |
831 | 831 | * parameters of the task might need updating. Otherwise, |
832 | 832 | * we want a replenishment of its runtime. |
833 | 833 | */ |
834 | - if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH) | |
835 | - replenish_dl_entity(dl_se, pi_se); | |
836 | - else | |
834 | + if (dl_se->dl_new || flags & ENQUEUE_WAKEUP) | |
837 | 835 | update_dl_entity(dl_se, pi_se); |
836 | + else if (flags & ENQUEUE_REPLENISH) | |
837 | + replenish_dl_entity(dl_se, pi_se); | |
838 | 838 | |
839 | 839 | __enqueue_dl_entity(dl_se); |
840 | 840 | } |