Commit-ID: 48be3a67da7413d62e5efbcf2c73a9dddf61fb96 Gitweb: http://git.kernel.org/tip/48be3a67da7413d62e5efbcf2c73a9dddf61fb96 Author: Peter Zijlstra <[email protected]> AuthorDate: Tue, 23 Feb 2016 13:28:22 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 29 Feb 2016 09:41:51 +0100
sched/deadline: Always calculate end of period on sched_yield() Steven noticed that occasionally a sched_yield() call would not result in a wait for the next period edge as expected. It turns out that when we call update_curr_dl() and end up with delta_exec <= 0, we will bail early and fail to throttle. Further inspection of the yield code revealed that yield_task_dl() clearing dl.runtime is wrong too, it will not account the last bit of runtime which could result in dl.runtime < 0, which in turn means that replenish would gift us with too much runtime. Fix both issues by not relying on the dl.runtime value for yield. Reported-by: Steven Rostedt <[email protected]> Tested-by: Steven Rostedt <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Clark Williams <[email protected]> Cc: Daniel Bristot de Oliveira <[email protected]> Cc: John Kacur <[email protected]> Cc: Juri Lelli <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/sched/deadline.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 57b939c..04a569c 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -399,6 +399,9 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se, dl_se->runtime = pi_se->dl_runtime; } + if (dl_se->dl_yielded && dl_se->runtime > 0) + dl_se->runtime = 0; + /* * We keep moving the deadline away until we get some * available runtime for the entity. This ensures correct @@ -735,8 +738,11 @@ 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)) + if (unlikely((s64)delta_exec <= 0)) { + if (unlikely(dl_se->dl_yielded)) + goto throttle; return; + } schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec)); @@ -749,8 +755,10 @@ static void update_curr_dl(struct rq *rq) sched_rt_avg_update(rq, delta_exec); - dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec; - if (dl_runtime_exceeded(dl_se)) { + dl_se->runtime -= delta_exec; + +throttle: + if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) { dl_se->dl_throttled = 1; __dequeue_task_dl(rq, curr, 0); if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr))) @@ -994,18 +1002,14 @@ static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) */ static void yield_task_dl(struct rq *rq) { - struct task_struct *p = rq->curr; - /* * We make the task go to sleep until its current deadline by * forcing its runtime to zero. This way, update_curr_dl() stops * it and the bandwidth timer will wake it up and will give it * new scheduling parameters (thanks to dl_yielded=1). */ - if (p->dl.runtime > 0) { - rq->curr->dl.dl_yielded = 1; - p->dl.runtime = 0; - } + rq->curr->dl.dl_yielded = 1; + update_rq_clock(rq); update_curr_dl(rq); /*
