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 fix all above and it adds a small skip in 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 <ktk...@parallels.com>
CC: Juri Lelli <juri.le...@gmail.com>
CC: Peter Zijlstra <pet...@infradead.org>
CC: Ingo Molnar <mi...@redhat.com>
---
kernel/sched/deadline.c | 10 ++++++++--
kernel/sched/rt.c | 7 +++++++
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e4f3ac3..27ef409 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 facc824..f3cee0a 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;
--
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