Commit 295d6d5e authored Sep 07, 2017 by Luca Abeni Committed by Ingo Molnar Oct 10, 2017

sched/deadline: Fix switching to -deadline



Fix a bug introduced in:

  72f9f3fd ("sched/deadline: Remove dl_new from struct sched_dl_entity")

After that commit, when switching to -deadline if the scheduling
deadline of a task is in the past then switched_to_dl() calls
setup_new_entity() to properly initialize the scheduling deadline
and runtime.

The problem is that the task is enqueued _before_ having its parameters
initialized by setup_new_entity(), and this can cause problems.
For example, a task with its out-of-date deadline in the past will
potentially be enqueued as the highest priority one; however, its
adjusted deadline may not be the earliest one.

This patch fixes the problem by initializing the task's parameters before
enqueuing it.

Signed-off-by: luca abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1504778971-13573-3-git-send-email-luca.abeni@santannapisa.it


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent e964d350

kernel/sched/deadline.c

+4 −7

Original line number	Diff line number	Diff line
		@@ -1364,6 +1364,10 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
		update_dl_entity(dl_se, pi_se);
		} else if (flags & ENQUEUE_REPLENISH) {
		replenish_dl_entity(dl_se, pi_se);
		} else if ((flags & ENQUEUE_RESTORE) &&
		dl_time_before(dl_se->deadline,
		rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
		setup_new_dl_entity(dl_se);
		}

		__enqueue_dl_entity(dl_se);
		@@ -2255,13 +2259,6 @@ static void switched_to_dl(struct rq rq, struct task_struct p)

		return;
		}
		/*
		* If p is boosted we already updated its params in
		* rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
		* p's deadline being now already after rq_clock(rq).
		*/
		if (dl_time_before(p->dl.deadline, rq_clock(rq)))
		setup_new_dl_entity(&p->dl);

		if (rq->curr != p) {
		#ifdef CONFIG_SMP

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