Commit 8fd5aa3b authored Dec 02, 2014 by Srivatsa Vaddagiri

sched: Fix inaccurate accounting for real-time task



It is possible that rq->clock_task was not updated in put_prev_task()
in which case we can potentially overcharge a real-time task for time
it did not run. This is because clock_task could be stale and not
represent the exact time real-time task started running.

Fix this by forcing update of rq->clock_task when real-time task
starts running.

Change-Id: I8320bb4e47924368583127b950d987925e8e6a6c
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>

parent 21357f54

kernel/sched/rt.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -1423,6 +1423,15 @@ static struct task_struct _pick_next_task_rt(struct rq rq)
		rt_rq = group_rt_rq(rt_se);
		} while (rt_rq);

		/*
		* Force update of rq->clock_task in case we failed to do so in
		* put_prev_task. A stale value can cause us to over-charge execution
		* time to real-time task, that could trigger throttling unnecessarily
		*/
		if (rq->skip_clock_update > 0) {
		rq->skip_clock_update = 0;
		update_rq_clock(rq);
		}
		p = rt_task_of(rt_se);
		p->se.exec_start = rq->clock_task;