path: root/Documentation/scheduler
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authorTommaso Cucinotta <>2016-09-09 19:45:17 +0200
committerIngo Molnar <>2016-09-10 11:17:41 +0200
commitb95202a3b6bb8715a716dbdb15cdb82bf622260b (patch)
tree0c31a7148c829fd9f52e2ccbc89c03a25be48442 /Documentation/scheduler
parentde58af878d9146e5decc0cdd7acabaa82881cbe4 (diff)
sched/deadline: Document behavior of sched_yield()
This is a documentation only patch, explaining the behavior of sched_yield() when a SCHED_DEADLINE task calls it (give up remaining runtime and be throttled until next period begins). Signed-off-by: Tommaso Cucinotta <> Signed-off-by: Peter Zijlstra (Intel) <> Reviewed-by: Juri Lelli <> Reviewed-by: Luca Abeni <> Reviewed-by: Daniel Bristot de Oliveira <> Cc: Juri Lelli <> Cc: Linus Torvalds <> Cc: Peter Zijlstra <> Cc: Thomas Gleixner <> Cc: Link: Signed-off-by: Ingo Molnar <>
Diffstat (limited to 'Documentation/scheduler')
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
index 53a2fe1ae8b8..8e37b0ba2c9d 100644
--- a/Documentation/scheduler/sched-deadline.txt
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -16,6 +16,7 @@ CONTENTS
4.1 System-wide settings
4.2 Task interface
4.3 Default behavior
+ 4.4 Behavior of sched_yield()
5. Tasks CPU affinity
5.1 SCHED_DEADLINE and cpusets HOWTO
6. Future plans
@@ -426,6 +427,23 @@ CONTENTS
Finally, notice that in order not to jeopardize the admission control a
-deadline task cannot fork.
+4.4 Behavior of sched_yield()
+ When a SCHED_DEADLINE task calls sched_yield(), it gives up its
+ remaining runtime and is immediately throttled, until the next
+ period, when its runtime will be replenished (a special flag
+ dl_yielded is set and used to handle correctly throttling and runtime
+ replenishment after a call to sched_yield()).
+ This behavior of sched_yield() allows the task to wake-up exactly at
+ the beginning of the next period. Also, this may be useful in the
+ future with bandwidth reclaiming mechanisms, where sched_yield() will
+ make the leftoever runtime available for reclamation by other
5. Tasks CPU affinity