Commit-ID: 734ff2a71f9e6aa6fedfa5a9a34818b8586516d5 Gitweb: http://git.kernel.org/tip/734ff2a71f9e6aa6fedfa5a9a34818b8586516d5 Author: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> AuthorDate: Tue, 4 Mar 2014 19:25:46 +0400 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 11 Mar 2014 12:05:35 +0100 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@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Juri Lelli <juri.lelli@xxxxxxxxx> Link: http://lkml.kernel.org/r/1393946746.3643.3.camel@tkhai Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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