Messages in this thread | | | Date | Thu, 11 Jul 2019 14:00:41 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH 3/6] sched/dl: Try better placement even for deadline tasks that do not block |
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On Thu, Jul 11, 2019 at 01:17:17PM +0200, Dietmar Eggemann wrote: > On 7/9/19 3:42 PM, Peter Zijlstra wrote:
> >>> That is, we only do those callbacks from: > >>> > >>> schedule_tail() > >>> __schedule() > >>> rt_mutex_setprio() > >>> __sched_setscheduler() > >>> > >>> and the above looks like it can happen outside of those.
> Is this what you are concerned about? > > (2 Cpus (CPU1, CPU2), 4 deadline task (thread0-X)) with > > @@ -1137,6 +1137,13 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf) > rf->cookie = lockdep_pin_lock(&rq->lock); > > #ifdef CONFIG_SCHED_DEBUG > +#ifdef CONFIG_SMP > + /* > + * There should not be pending callbacks at the start of rq_lock(); > + * all sites that handle them flush them at the end. > + */ > + WARN_ON_ONCE(rq->balance_callback); > +#endif > > > [ 87.251237] *** <--- queue_balance_callback(migrate_dl_task) p=[thread0-3 3627] on CPU2 > [ 87.251261] WARNING: CPU: 2 PID: 3627 at kernel/sched/sched.h:1145 __schedule+0x56c/0x690 > [ 87.615882] WARNING: CPU: 2 PID: 3616 at kernel/sched/sched.h:1145 task_rq_lock+0xe8/0xf0 > [ 88.176844] WARNING: CPU: 2 PID: 3616 at kernel/sched/sched.h:1145 load_balance+0x4d0/0xbc0 > [ 88.381905] WARNING: CPU: 2 PID: 3616 at kernel/sched/sched.h:1145 load_balance+0x7d8/0xbc0
I'm not sure how we get 4 warns, I was thinking that as soon as we exit __schedule() we'd procress the callback so further warns would be avoided.
> [ 88.586991] *** ---> migrate_dl_task() p=[thread0-3 3627] to CPU1
But yes, something like this. Basucally I want to avoid calling queue_balance_callback() from a context where we'll not follow up with balance_callback().
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