sched: Allow SCHED_BATCH to preempt SCHED_IDLE tasks
Perform the test for SCHED_IDLE before testing for SCHED_BATCH (and
ensure idle tasks don't preempt idle tasks) so the non-interactive,
but still important, SCHED_BATCH tasks will run in favor of the very
low priority SCHED_IDLE tasks.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
LKML-Reference: <1298408674-3130-2-git-send-email-dvhart@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3a88dee..1438e13 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1870,16 +1870,18 @@
if (test_tsk_need_resched(curr))
return;
+ /* Idle tasks are by definition preempted by non-idle tasks. */
+ if (unlikely(curr->policy == SCHED_IDLE) &&
+ likely(p->policy != SCHED_IDLE))
+ goto preempt;
+
/*
- * Batch and idle tasks do not preempt (their preemption is driven by
- * the tick):
+ * Batch and idle tasks do not preempt non-idle tasks (their preemption
+ * is driven by the tick):
*/
if (unlikely(p->policy != SCHED_NORMAL))
return;
- /* Idle tasks are by definition preempted by everybody. */
- if (unlikely(curr->policy == SCHED_IDLE))
- goto preempt;
if (!sched_feat(WAKEUP_PREEMPT))
return;