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| author | Mike Galbraith <efault@gmx.de> | 2011-01-05 05:41:17 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-01-18 15:09:44 +0100 |
| commit | d7d8294415f0ce4254827d4a2a5ee88b00be52a8 (patch) | |
| tree | 9f8024d6566bc391fcb2aced8427db81ca4e9078 | |
| parent | fce2097983d914ea8c2338efc6f6e9bb737f6ae4 (diff) | |
| download | lwn-d7d8294415f0ce4254827d4a2a5ee88b00be52a8.tar.gz lwn-d7d8294415f0ce4254827d4a2a5ee88b00be52a8.zip | |
sched: Fix signed unsigned comparison in check_preempt_tick()
Signed unsigned comparison may lead to superfluous resched if leftmost
is right of the current task, wasting a few cycles, and inadvertently
_lengthening_ the current task's slice.
Reported-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294202477.9384.5.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | kernel/sched_fair.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 414145cf5344..77e9166d7bbf 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1062,6 +1062,9 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) struct sched_entity *se = __pick_next_entity(cfs_rq); s64 delta = curr->vruntime - se->vruntime; + if (delta < 0) + return; + if (delta > ideal_runtime) resched_task(rq_of(cfs_rq)->curr); } |