From: Peter Zijlstra <peterz@infradead.org>
To: Luca Abeni <luca.abeni@santannapisa.it>
Cc: linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Joel Fernandes <joel@joelfernandes.org>,
Quentin Perret <quentin.perret@arm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Juri Lelli <juri.lelli@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
Subject: Re: [RFC PATCH 3/6] sched/dl: Try better placement even for deadline tasks that do not block
Date: Mon, 8 Jul 2019 15:55:36 +0200 [thread overview]
Message-ID: <20190708135536.GK3402@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190506044836.2914-4-luca.abeni@santannapisa.it>
On Mon, May 06, 2019 at 06:48:33AM +0200, Luca Abeni wrote:
> @@ -1223,8 +1250,17 @@ static void update_curr_dl(struct rq *rq)
> dl_se->dl_overrun = 1;
>
> __dequeue_task_dl(rq, curr, 0);
> - if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
> + if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr))) {
> enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
> +#ifdef CONFIG_SMP
> + } else if (dl_se->dl_adjust) {
> + if (rq->migrating_task == NULL) {
> + queue_balance_callback(rq, &per_cpu(dl_migrate_head, rq->cpu), migrate_dl_task);
I'm not entirely sure about this one.
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.
The pattern in those sites is:
rq_lock();
... do crap that leads to queue_balance_callback()
rq_unlock()
if (rq->balance_callback) {
raw_spin_lock_irqsave(rq->lock, flags);
... do callbacks
raw_spin_unlock_irqrestore(rq->lock, flags);
}
So I suppose can catch abuse of this API by doing something like the
below; can you validate?
---
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index aaca0e743776..89e615f1eae6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1134,6 +1134,14 @@ 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
+
rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
rf->clock_update_flags = 0;
#endif
next prev parent reply other threads:[~2019-07-08 13:55 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 4:48 [RFC PATCH 0/6] Capacity awareness for SCHED_DEADLINE Luca Abeni
2019-05-06 4:48 ` [RFC PATCH 1/6] sched/dl: Improve deadline admission control for asymmetric CPU capacities Luca Abeni
2019-05-07 13:48 ` Quentin Perret
2019-05-07 13:55 ` Vincent Guittot
2019-05-07 14:02 ` Quentin Perret
2019-05-07 14:25 ` luca abeni
2019-05-07 14:31 ` Quentin Perret
2019-05-07 14:43 ` luca abeni
2019-07-08 11:22 ` Dietmar Eggemann
2019-07-08 15:05 ` Quentin Perret
2019-06-18 16:41 ` Alessio Balsini
2019-05-06 4:48 ` [RFC PATCH 2/6] sched/dl: Capacity-aware migrations Luca Abeni
2019-05-07 13:35 ` Quentin Perret
2019-05-07 14:17 ` luca abeni
2019-05-07 15:04 ` Quentin Perret
2019-05-07 14:10 ` Quentin Perret
2019-05-07 14:41 ` luca abeni
2019-05-07 15:02 ` Quentin Perret
2019-05-08 8:04 ` Juri Lelli
2019-05-08 8:17 ` luca abeni
2019-07-04 12:05 ` Dietmar Eggemann
2019-07-08 7:41 ` luca abeni
2019-07-08 10:41 ` Dietmar Eggemann
2019-05-06 4:48 ` [RFC PATCH 3/6] sched/dl: Try better placement even for deadline tasks that do not block Luca Abeni
2019-05-07 14:13 ` Quentin Perret
2019-05-07 16:00 ` Morten Rasmussen
2019-05-08 8:01 ` Juri Lelli
2019-05-08 8:14 ` luca abeni
2019-05-08 9:22 ` Juri Lelli
2019-07-08 13:55 ` Peter Zijlstra [this message]
2019-07-09 13:24 ` luca abeni
2019-07-09 13:42 ` Peter Zijlstra
2019-07-11 11:17 ` Dietmar Eggemann
2019-07-11 12:00 ` Peter Zijlstra
2019-07-11 15:33 ` Dietmar Eggemann
2019-07-09 14:44 ` Dietmar Eggemann
2019-05-06 4:48 ` [RFC PATCH 4/6] sched/dl: Improve capacity-aware wakeup Luca Abeni
2019-05-08 9:08 ` Juri Lelli
2019-05-08 9:24 ` luca abeni
2019-05-08 12:05 ` Juri Lelli
2019-05-08 12:47 ` luca abeni
2019-05-08 13:10 ` Juri Lelli
2019-05-08 14:12 ` luca abeni
2019-05-06 4:48 ` [RFC PATCH 5/6] sched/dl: If the task does not fit anywhere, select the fastest core Luca Abeni
2019-05-06 4:48 ` [RFC PATCH 6/6] sched/dl: Try not to select a too fast core Luca Abeni
2019-05-07 15:57 ` Quentin Perret
2019-05-08 6:26 ` luca abeni
2019-05-09 13:46 ` Quentin Perret
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