[PATCH v2] simplify new deadline tasks detection

[PATCH v2] simplify new deadline tasks detection

[Luca Abeni]

This is v2 of my previous patch removing dl_new; repect to
the previos version, I (hopeflly) fixed all the coding style
issues (now scripts/checkpatch.pl reports 0 warinngs and 0 errors).
The patch has been tested with Juri's deadline tests and
some other tests based on periodic real-time threads, and the
tests did not show any regressions respect to git master.


Luca Abeni (1):
  sched/deadline: remove dl_new from sched_dl_entity

 include/linux/sched.h   |  6 +-----
 kernel/sched/core.c     |  1 -
 kernel/sched/deadline.c | 35 +++++++++++++----------------------
 3 files changed, 14 insertions(+), 28 deletions(-)

-- 
2.5.0

[PATCH v2] sched/deadline: remove dl_new from sched_dl_entity

[Luca Abeni]

The dl_new field of the sched_dl_entity is currently used to
identify new deadline tasks, so that their deadline and runtime
can be properly initialised.
However, these tasks can be easily identified by checking if
their deadline is smaller than the current time when they switch
to SCHED_DEADLINE. So, dl_new can be removed by introducing this
check in switched_to_dl(); this allows to simplify the
SCHED_DEADLINE code.

Signed-off-by: Luca Abeni <luca.abeni@unitn.it>
---
 include/linux/sched.h   |  6 +-----
 kernel/sched/core.c     |  1 -
 kernel/sched/deadline.c | 35 +++++++++++++----------------------
 3 files changed, 14 insertions(+), 28 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a10494a..3a66e15 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1329,10 +1329,6 @@ struct sched_dl_entity {
 	 * task has to wait for a replenishment to be performed at the
 	 * next firing of dl_timer.
 	 *
-	 * @dl_new tells if a new instance arrived. If so we must
-	 * start executing it with full runtime and reset its absolute
-	 * deadline;
-	 *
 	 * @dl_boosted tells if we are boosted due to DI. If so we are
 	 * outside bandwidth enforcement mechanism (but only until we
 	 * exit the critical section);
@@ -1340,7 +1336,7 @@ struct sched_dl_entity {
 	 * @dl_yielded tells if task gave up the cpu before consuming
 	 * all its available runtime during the last job.
 	 */
-	int dl_throttled, dl_new, dl_boosted, dl_yielded;
+	int dl_throttled, dl_boosted, dl_yielded;
 
 	/*
 	 * Bandwidth enforcement timer. Each -deadline task has its
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9503d59..7d5a2bd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2183,7 +2183,6 @@ void __dl_clear_params(struct task_struct *p)
 	dl_se->dl_bw = 0;
 
 	dl_se->dl_throttled = 0;
-	dl_se->dl_new = 1;
 	dl_se->dl_yielded = 0;
 }
 
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 57b939c..f565a72 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -352,7 +352,15 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
-	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
+	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
+
+	/*
+	 * We are racing with the deadline timer. So, do nothing because
+	 * the deadline timer handler will take care of properly recharging
+	 * the runtime and postponing the deadline
+	 */
+	if (dl_se->dl_throttled)
+		return;
 
 	/*
 	 * We use the regular wall clock time to set deadlines in the
@@ -361,7 +369,6 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
 	 */
 	dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
 	dl_se->runtime = pi_se->dl_runtime;
-	dl_se->dl_new = 0;
 }
 
 /*
@@ -500,15 +507,6 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
-	/*
-	 * The arrival of a new instance needs special treatment, i.e.,
-	 * the actual scheduling parameters have to be "renewed".
-	 */
-	if (dl_se->dl_new) {
-		setup_new_dl_entity(dl_se, pi_se);
-		return;
-	}
-
 	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
 	    dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
 		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
@@ -605,16 +603,6 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 	}
 
 	/*
-	 * This is possible if switched_from_dl() raced against a running
-	 * callback that took the above !dl_task() path and we've since then
-	 * switched back into SCHED_DEADLINE.
-	 *
-	 * There's nothing to do except drop our task reference.
-	 */
-	if (dl_se->dl_new)
-		goto unlock;
-
-	/*
 	 * The task might have been boosted by someone else and might be in the
 	 * boosting/deboosting path, its not throttled.
 	 */
@@ -917,7 +905,7 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
 	 * parameters of the task might need updating. Otherwise,
 	 * we want a replenishment of its runtime.
 	 */
-	if (dl_se->dl_new || flags & ENQUEUE_WAKEUP)
+	if (flags & ENQUEUE_WAKEUP)
 		update_dl_entity(dl_se, pi_se);
 	else if (flags & ENQUEUE_REPLENISH)
 		replenish_dl_entity(dl_se, pi_se);
@@ -1722,6 +1710,9 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
  */
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
+	if (dl_time_before(p->dl.deadline, rq_clock(rq)))
+		setup_new_dl_entity(&p->dl, &p->dl);
+
 	if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
 		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
-- 
2.5.0

[tip:sched/core] sched/deadline: Remove dl_new from struct sched_dl_entity

[tip-bot for Luca Abeni]

Commit-ID:  72f9f3fdc928dc3ecd223e801b32d930b662b6ed
Gitweb:     http://git.kernel.org/tip/72f9f3fdc928dc3ecd223e801b32d930b662b6ed
Author:     Luca Abeni <luca.abeni@unitn.it>
AuthorDate: Mon, 7 Mar 2016 12:27:04 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 8 Mar 2016 12:24:55 +0100

sched/deadline: Remove dl_new from struct sched_dl_entity

The dl_new field of struct sched_dl_entity is currently used to
identify new deadline tasks, so that their deadline and runtime
can be properly initialised.

However, these tasks can be easily identified by checking if
their deadline is smaller than the current time when they switch
to SCHED_DEADLINE. So, dl_new can be removed by introducing this
check in switched_to_dl(); this allows to simplify the
SCHED_DEADLINE code.

Signed-off-by: Luca Abeni <luca.abeni@unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1457350024-7825-2-git-send-email-luca.abeni@unitn.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/sched.h   |  6 +-----
 kernel/sched/core.c     |  1 -
 kernel/sched/deadline.c | 35 +++++++++++++----------------------
 3 files changed, 14 insertions(+), 28 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9519b66..838a89a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1333,10 +1333,6 @@ struct sched_dl_entity {
 	 * task has to wait for a replenishment to be performed at the
 	 * next firing of dl_timer.
 	 *
-	 * @dl_new tells if a new instance arrived. If so we must
-	 * start executing it with full runtime and reset its absolute
-	 * deadline;
-	 *
 	 * @dl_boosted tells if we are boosted due to DI. If so we are
 	 * outside bandwidth enforcement mechanism (but only until we
 	 * exit the critical section);
@@ -1344,7 +1340,7 @@ struct sched_dl_entity {
 	 * @dl_yielded tells if task gave up the cpu before consuming
 	 * all its available runtime during the last job.
 	 */
-	int dl_throttled, dl_new, dl_boosted, dl_yielded;
+	int dl_throttled, dl_boosted, dl_yielded;
 
 	/*
 	 * Bandwidth enforcement timer. Each -deadline task has its
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 423452c..249e37d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2051,7 +2051,6 @@ void __dl_clear_params(struct task_struct *p)
 	dl_se->dl_bw = 0;
 
 	dl_se->dl_throttled = 0;
-	dl_se->dl_new = 1;
 	dl_se->dl_yielded = 0;
 }
 
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 15abf04..c7a036f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -352,7 +352,15 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
-	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
+	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
+
+	/*
+	 * We are racing with the deadline timer. So, do nothing because
+	 * the deadline timer handler will take care of properly recharging
+	 * the runtime and postponing the deadline
+	 */
+	if (dl_se->dl_throttled)
+		return;
 
 	/*
 	 * We use the regular wall clock time to set deadlines in the
@@ -361,7 +369,6 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
 	 */
 	dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
 	dl_se->runtime = pi_se->dl_runtime;
-	dl_se->dl_new = 0;
 }
 
 /*
@@ -503,15 +510,6 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
-	/*
-	 * The arrival of a new instance needs special treatment, i.e.,
-	 * the actual scheduling parameters have to be "renewed".
-	 */
-	if (dl_se->dl_new) {
-		setup_new_dl_entity(dl_se, pi_se);
-		return;
-	}
-
 	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
 	    dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
 		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
@@ -608,16 +606,6 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 	}
 
 	/*
-	 * This is possible if switched_from_dl() raced against a running
-	 * callback that took the above !dl_task() path and we've since then
-	 * switched back into SCHED_DEADLINE.
-	 *
-	 * There's nothing to do except drop our task reference.
-	 */
-	if (dl_se->dl_new)
-		goto unlock;
-
-	/*
 	 * The task might have been boosted by someone else and might be in the
 	 * boosting/deboosting path, its not throttled.
 	 */
@@ -925,7 +913,7 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
 	 * parameters of the task might need updating. Otherwise,
 	 * we want a replenishment of its runtime.
 	 */
-	if (dl_se->dl_new || flags & ENQUEUE_WAKEUP)
+	if (flags & ENQUEUE_WAKEUP)
 		update_dl_entity(dl_se, pi_se);
 	else if (flags & ENQUEUE_REPLENISH)
 		replenish_dl_entity(dl_se, pi_se);
@@ -1726,6 +1714,9 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
  */
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
+	if (dl_time_before(p->dl.deadline, rq_clock(rq)))
+		setup_new_dl_entity(&p->dl, &p->dl);
+
 	if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
 		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)