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

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Date:   Wed, 10 May 2017 21:03:37 +0800
From:   Xunlei Pang <xlpang@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Xunlei Pang <xlpang@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: [PATCH] sched/deadline: Zero out positive runtime after throttling constrained tasks

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.

Fixes: df8eac8cafce ("sched/deadline: Throttle a constrained deadline task activated after the deadline)
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Signed-off-by: Xunlei Pang <xlpang@...hat.com>
---
 kernel/sched/deadline.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index a2ce590..d3d291e 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -723,6 +723,8 @@ static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
 		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;
 	}
 }
 
-- 
1.8.3.1