linux-kernel - [PATCH 4.4 29/53] sched/deadline: Zero out positive runtime after throttling constrained tasks

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Date:   Mon, 22 Jan 2018 09:40:21 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xunlei Pang <xlpang@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Mike Galbraith <efault@....de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 4.4 29/53] sched/deadline: Zero out positive runtime after throttling constrained tasks

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

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

From: Xunlei Pang <xlpang@...hat.com>

commit ae83b56a56f8d9643dedbee86b457fa1c5d42f59 upstream.

When a contrained task is throttled by dl_check_constrained_dl(),
it may carry the remaining positive runtime, as a result when
dl_task_timer() fires and calls replenish_dl_entity(), it will
not be replenished correctly due to the positive dl_se->runtime.

This patch assigns its runtime to 0 if positive after throttling.

Signed-off-by: Xunlei Pang <xlpang@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Juri Lelli <juri.lelli@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luca Abeni <luca.abeni@...tannapisa.it>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Fixes: df8eac8cafce ("sched/deadline: Throttle a constrained deadline task activated after the deadline)
Link: http://lkml.kernel.org/r/1494421417-27550-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/deadline.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -732,6 +732,8 @@ static inline void dl_check_constrained_
 		if (unlikely(dl_se->dl_boosted || !start_dl_timer(p)))
 			return;
 		dl_se->dl_throttled = 1;
+		if (dl_se->runtime > 0)
+			dl_se->runtime = 0;
 	}
 }