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authorLinus Torvalds <torvalds@g5.osdl.org>2006-05-21 18:54:09 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-21 18:54:09 -0700
commitf1adad78dd2fc8edaa513e0bde92b4c64340245c (patch)
treea2cd5c53b08fa80c953147ee22b62e7bbff7ddcd /kernel/sched.c
parentc9d20af62c59e49684f3882503351153964ff14b (diff)
Revert "[PATCH] sched: fix interactive task starvation"
This reverts commit 5ce74abe788a26698876e66b9c9ce7e7acc25413 (and its dependent commit 8a5bc075b8d8cf7a87b3f08fad2fba0f5d13295e), because of audio underruns. Reported by Rene Herman <rene.herman@keyaccess.nl>, who also pinpointed the exact cause of the underruns: "Audio underruns galore, with only ogg123 and firefox (browsing the GIT tree online is also a nice trigger by the way). If I back it out, everything is fine for me again." Cc: Rene Herman <rene.herman@keyaccess.nl> Cc: Mike Galbraith <efault@gmx.de> Acked-by: Con Kolivas <kernel@kolivas.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c62
1 files changed, 18 insertions, 44 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 4c64f85698a..c13f1bd2df7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -665,55 +665,13 @@ static int effective_prio(task_t *p)
}
/*
- * We place interactive tasks back into the active array, if possible.
- *
- * To guarantee that this does not starve expired tasks we ignore the
- * interactivity of a task if the first expired task had to wait more
- * than a 'reasonable' amount of time. This deadline timeout is
- * load-dependent, as the frequency of array switched decreases with
- * increasing number of running tasks. We also ignore the interactivity
- * if a better static_prio task has expired, and switch periodically
- * regardless, to ensure that highly interactive tasks do not starve
- * the less fortunate for unreasonably long periods.
- */
-static inline int expired_starving(runqueue_t *rq)
-{
- int limit;
-
- /*
- * Arrays were recently switched, all is well
- */
- if (!rq->expired_timestamp)
- return 0;
-
- limit = STARVATION_LIMIT * rq->nr_running;
-
- /*
- * It's time to switch arrays
- */
- if (jiffies - rq->expired_timestamp >= limit)
- return 1;
-
- /*
- * There's a better selection in the expired array
- */
- if (rq->curr->static_prio > rq->best_expired_prio)
- return 1;
-
- /*
- * All is well
- */
- return 0;
-}
-
-/*
* __activate_task - move a task to the runqueue.
*/
static void __activate_task(task_t *p, runqueue_t *rq)
{
prio_array_t *target = rq->active;
- if (unlikely(batch_task(p) || (expired_starving(rq) && !rt_task(p))))
+ if (batch_task(p))
target = rq->expired;
enqueue_task(p, target);
rq->nr_running++;
@@ -2532,6 +2490,22 @@ unsigned long long current_sched_time(const task_t *tsk)
}
/*
+ * We place interactive tasks back into the active array, if possible.
+ *
+ * To guarantee that this does not starve expired tasks we ignore the
+ * interactivity of a task if the first expired task had to wait more
+ * than a 'reasonable' amount of time. This deadline timeout is
+ * load-dependent, as the frequency of array switched decreases with
+ * increasing number of running tasks. We also ignore the interactivity
+ * if a better static_prio task has expired:
+ */
+#define EXPIRED_STARVING(rq) \
+ ((STARVATION_LIMIT && ((rq)->expired_timestamp && \
+ (jiffies - (rq)->expired_timestamp >= \
+ STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
+ ((rq)->curr->static_prio > (rq)->best_expired_prio))
+
+/*
* Account user cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
@@ -2666,7 +2640,7 @@ void scheduler_tick(void)
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
- if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
+ if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
enqueue_task(p, rq->expired);
if (p->static_prio < rq->best_expired_prio)
rq->best_expired_prio = p->static_prio;