linux-kernel - [PATCH 4.14 097/115] sched/deadline: Fix switching to -deadline

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Date:   Thu, 13 Sep 2018 15:31:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, luca abeni <luca.abeni@...tannapisa.it>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Galbraith <efault@....de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH 4.14 097/115] sched/deadline: Fix switching to -deadline

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Luca Abeni <luca.abeni@...tannapisa.it>

commit 295d6d5e373607729bcc8182c25afe964655714f upstream.

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For example, a task with its out-of-date deadline in the past will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>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/deadline.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1365,6 +1365,10 @@ enqueue_dl_entity(struct sched_dl_entity
 		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);
@@ -2256,13 +2260,6 @@ static void switched_to_dl(struct rq *rq
 
 		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