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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xunlei Pang <xlpang@redhat.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Juri Lelli <juri.lelli@arm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Luca Abeni <luca.abeni@santannapisa.it>,
        Mike Galbraith <efault@gmx.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Ben Hutchings <ben.hutchings@codethink.co.uk>
Subject: [PATCH 4.9 13/47] sched/deadline: Zero out positive runtime after throttling constrained tasks
Date:   Mon, 22 Jan 2018 09:45:24 +0100
Message-Id: <20180122083926.584172432@linuxfoundation.org>
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References: <20180122083925.568134913@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Xunlei Pang <xlpang@redhat.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@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.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@kernel.org>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -723,6 +723,8 @@ 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;
 	}
 }