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.

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>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e3b25dfb74f36a6ee62b6fa32dc5706e48db3799..54302cf68bb96dabbc9d925873740822cb12b7c1 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -941,6 +941,8 @@ 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;
        }
 }