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authorKirill Tkhai <ktkhai@parallels.com>2014-03-04 19:25:46 +0400
committerIngo Molnar <mingo@kernel.org>2014-03-11 12:05:35 +0100
commit734ff2a71f9e6aa6fedfa5a9a34818b8586516d5 (patch)
tree50ee9626f98a1849c98a6d7308e259e4ad93b889 /kernel
parenta02ed5e3e05ec5e8af21e645cccc77f3a6480aaf (diff)
downloadlinux-734ff2a71f9e6aa6fedfa5a9a34818b8586516d5.tar.bz2
sched/rt: Fix picking RT and DL tasks from empty queue
The problems: 1) We check for rt_nr_running before call of put_prev_task(). If previous task is RT, its rt_rq may become throttled and dequeued after this call. In case of p is from rt->rq this just causes picking a task from throttled queue, but in case of its rt_rq is child we are guaranteed catch BUG_ON. 2) The same with deadline class. The only difference we operate on only dl_rq. This patch fixes all the above problems and it adds a small skip in the DL update like we've already done for RT class: if (unlikely((s64)delta_exec <= 0)) return; This will optimize sequential update_curr_dl() calls a little. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Link: http://lkml.kernel.org/r/1393946746.3643.3.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/deadline.c10
-rw-r--r--kernel/sched/rt.c7
2 files changed, 15 insertions, 2 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e4f3ac3b8514..27ef40925525 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -609,8 +609,8 @@ static void update_curr_dl(struct rq *rq)
* approach need further study.
*/
delta_exec = rq_clock_task(rq) - curr->se.exec_start;
- if (unlikely((s64)delta_exec < 0))
- delta_exec = 0;
+ if (unlikely((s64)delta_exec <= 0))
+ return;
schedstat_set(curr->se.statistics.exec_max,
max(curr->se.statistics.exec_max, delta_exec));
@@ -1023,6 +1023,12 @@ struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
if (need_pull_dl_task(rq, prev))
pull_dl_task(rq);
+ /*
+ * When prev is DL, we may throttle it in put_prev_task().
+ * So, we update time before we check for dl_nr_running.
+ */
+ if (prev->sched_class == &dl_sched_class)
+ update_curr_dl(rq);
if (unlikely(!dl_rq->dl_nr_running))
return NULL;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index facc824334fb..f3cee0a63b76 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1379,6 +1379,13 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev)
return RETRY_TASK;
}
+ /*
+ * We may dequeue prev's rt_rq in put_prev_task().
+ * So, we update time before rt_nr_running check.
+ */
+ if (prev->sched_class == &rt_sched_class)
+ update_curr_rt(rq);
+
if (!rt_rq->rt_nr_running)
return NULL;