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| author | Ingo Molnar <mingo@elte.hu> | 2007-02-28 20:13:42 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-01 14:53:38 -0800 |
| commit | 7355690ead6d61f6344072ae61060f985060da29 (patch) | |
| tree | a8cd9d89ed0a34b6d81399eae0999a0cafa63ed8 /kernel/sched.c | |
| parent | 3f555c700b6c90f9ac24bc81a4f509583d906278 (diff) | |
| download | op-kernel-dev-7355690ead6d61f6344072ae61060f985060da29.zip op-kernel-dev-7355690ead6d61f6344072ae61060f985060da29.tar.gz | |
[PATCH] sched: fix SMT scheduler bug
The SMT scheduler incorrectly skips kernel threads even if they are
runnable (but they are preempted by a higher-prio user-space task which got
SMT-delayed by an even higher-priority task running on a sibling CPU).
Fix this for now by only doing the SMT-nice optimization if the
to-be-delayed task is the only runnable task. (This should cover most of
the real-life cases anyway.)
This bug has been in the SMT scheduler since 2.6.17 or so, but has only
been noticed now by the active check in the dynticks code.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 0c5ebf5..5f102e6 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3547,7 +3547,7 @@ need_resched_nonpreemptible: } } next->sleep_type = SLEEP_NORMAL; - if (dependent_sleeper(cpu, rq, next)) + if (rq->nr_running == 1 && dependent_sleeper(cpu, rq, next)) next = rq->idle; switch_tasks: if (next == rq->idle) |
