Messages in this thread Patch in this message | | | Date | Fri, 21 Feb 2014 11:37:15 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC] sched/deadline: Prevent rt_time growth to infinity |
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On Thu, Feb 20, 2014 at 02:16:00AM +0400, Kirill Tkhai wrote: > Since deadline tasks share rt bandwidth, we must care about > bandwidth timer set. Otherwise rt_time may grow up to infinity > in update_curr_dl(), if there are no other available RT tasks > on top level bandwidth. > > I'm going to decide the problem the way below. Almost untested > because of I skipped almost all of recent patches which haveto be applied from lkml. > > Please say, if I skipped anything in idea. Maybe better put > start_top_rt_bandwidth() into set_curr_task_dl()?
How about we only increment rt_time when there's an RT bandwidth timer active?
--- --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -568,6 +568,12 @@ static inline struct rt_bandwidth *sched #endif /* CONFIG_RT_GROUP_SCHED */ +bool sched_rt_bandwidth_active(struct rt_rq *rt_rq) +{ + struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq); + return hrtimer_active(&rt_b->rt_period_timer); +} + #ifdef CONFIG_SMP /* * We ran out of runtime, see if we can borrow some from our neighbours. --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -587,6 +587,8 @@ int dl_runtime_exceeded(struct rq *rq, s return 1; } +extern bool sched_rt_bandwidth_active(struct rt_rq *rt_rq); + /* * Update the current task's runtime statistics (provided it is still * a -deadline task and has not been removed from the dl_rq). @@ -650,11 +652,13 @@ static void update_curr_dl(struct rq *rq struct rt_rq *rt_rq = &rq->rt; raw_spin_lock(&rt_rq->rt_runtime_lock); - rt_rq->rt_time += delta_exec; /* * We'll let actual RT tasks worry about the overflow here, we - * have our own CBS to keep us inline -- see above. + * have our own CBS to keep us inline; only account when RT + * bandwidth is relevant. */ + if (sched_rt_bandwidth_active(rt_rq)) + rt_rq->rt_time += delta_exec; raw_spin_unlock(&rt_rq->rt_runtime_lock); } }
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