linux-kernel - [tip:sched/core] sched/deadline: Fix switching to -deadline

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Date:   Tue, 10 Oct 2017 03:56:12 -0700
From:   tip-bot for Luca Abeni <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bristot@...hat.com, peterz@...radead.org,
        mathieu.poirier@...aro.org, linux-kernel@...r.kernel.org,
        hpa@...or.com, efault@....de, mingo@...nel.org, juri.lelli@....com,
        rostedt@...dmis.org, tglx@...utronix.de,
        luca.abeni@...tannapisa.it, torvalds@...ux-foundation.org
Subject: [tip:sched/core] sched/deadline: Fix switching to -deadline

Commit-ID:  295d6d5e373607729bcc8182c25afe964655714f
Gitweb:     https://git.kernel.org/tip/295d6d5e373607729bcc8182c25afe964655714f
Author:     Luca Abeni <luca.abeni@...tannapisa.it>
AuthorDate: Thu, 7 Sep 2017 12:09:29 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 10 Oct 2017 11:43:30 +0200

sched/deadline: Fix switching to -deadline

Fix a bug introduced in:

  72f9f3fdc928 ("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For example, a task with its out-of-date deadline in the past will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@...tannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Juri Lelli <juri.lelli@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1504778971-13573-3-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/deadline.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0191ec7..9d45354 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -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