[patch 0/3] sched: Make Priority Inheritance POSIX compliant

[patch 0/3] sched: Make Priority Inheritance POSIX compliant

[Thomas Gleixner]

The current PI implementation violates POSIX scheduling semantics when
a thread is deboosted. The following patch series adresses this.

Thanks and Kudos go to Mathias Weber and Carsten Emde for analysis,
test cases and initial workaround patches.

Thanks,

	tglx

[patch 1/3] sched: Extend enqueue_task to allow head queueing

[Thomas Gleixner]

[-- Attachment #1: sched-extend-enqueue-task-to-allow-head-queueing.patch --]
[-- Type: text/plain, Size: 3812 bytes --]

The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Extend the related functions with a "head" argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/sched.h |    3 ++-
 kernel/sched.c        |   13 +++++++------
 kernel/sched_fair.c   |    3 ++-
 kernel/sched_rt.c     |    3 ++-
 4 files changed, 13 insertions(+), 9 deletions(-)

Index: linux-2.6-tip/include/linux/sched.h
===================================================================
--- linux-2.6-tip.orig/include/linux/sched.h
+++ linux-2.6-tip/include/linux/sched.h
@@ -1075,7 +1075,8 @@ struct sched_domain;
 struct sched_class {
 	const struct sched_class *next;
 
-	void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup);
+	void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup,
+			      bool head);
 	void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep);
 	void (*yield_task) (struct rq *rq);
 
Index: linux-2.6-tip/kernel/sched.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched.c
+++ linux-2.6-tip/kernel/sched.c
@@ -1883,13 +1883,14 @@ static void update_avg(u64 *avg, u64 sam
 	*avg += diff >> 3;
 }
 
-static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	if (wakeup)
 		p->se.start_runtime = p->se.sum_exec_runtime;
 
 	sched_info_queued(p);
-	p->sched_class->enqueue_task(rq, p, wakeup);
+	p->sched_class->enqueue_task(rq, p, wakeup, head);
 	p->se.on_rq = 1;
 }
 
@@ -1965,7 +1966,7 @@ static void activate_task(struct rq *rq,
 	if (task_contributes_to_load(p))
 		rq->nr_uninterruptible--;
 
-	enqueue_task(rq, p, wakeup);
+	enqueue_task(rq, p, wakeup, false);
 	inc_nr_running(rq);
 }
 
@@ -6065,7 +6066,7 @@ void rt_mutex_setprio(struct task_struct
 	if (running)
 		p->sched_class->set_curr_task(rq);
 	if (on_rq) {
-		enqueue_task(rq, p, 0);
+		enqueue_task(rq, p, 0, false);
 
 		check_class_changed(rq, p, prev_class, oldprio, running);
 	}
@@ -6109,7 +6110,7 @@ void set_user_nice(struct task_struct *p
 	delta = p->prio - old_prio;
 
 	if (on_rq) {
-		enqueue_task(rq, p, 0);
+		enqueue_task(rq, p, 0, false);
 		/*
 		 * If the task increased its priority or is running and
 		 * lowered its priority, then reschedule its CPU:
@@ -10110,7 +10111,7 @@ void sched_move_task(struct task_struct 
 	if (unlikely(running))
 		tsk->sched_class->set_curr_task(rq);
 	if (on_rq)
-		enqueue_task(rq, tsk, 0);
+		enqueue_task(rq, tsk, 0, false);
 
 	task_rq_unlock(rq, &flags);
 }
Index: linux-2.6-tip/kernel/sched_fair.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched_fair.c
+++ linux-2.6-tip/kernel/sched_fair.c
@@ -1053,7 +1053,8 @@ static inline void hrtick_update(struct 
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
-static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se = &p->se;
Index: linux-2.6-tip/kernel/sched_rt.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched_rt.c
+++ linux-2.6-tip/kernel/sched_rt.c
@@ -878,7 +878,8 @@ static void dequeue_rt_entity(struct sch
 /*
  * Adding/removing a task to/from a priority array:
  */
-static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	struct sched_rt_entity *rt_se = &p->rt;
 

[tip:sched/core] sched: Extend enqueue_task to allow head queueing

[tip-bot for Thomas Gleixner]

Commit-ID:  ea87bb7853168434f4a82426dd1ea8421f9e604d
Gitweb:     http://git.kernel.org/tip/ea87bb7853168434f4a82426dd1ea8421f9e604d
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 20 Jan 2010 20:58:57 +0000
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 22 Jan 2010 18:09:59 +0100

sched: Extend enqueue_task to allow head queueing

The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Extend the related functions with a "head" argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.734886007@linutronix.de>

---
 include/linux/sched.h |    3 ++-
 kernel/sched.c        |   13 +++++++------
 kernel/sched_fair.c   |    3 ++-
 kernel/sched_rt.c     |    3 ++-
 4 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8b07973..b35c0c7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1067,7 +1067,8 @@ struct sched_domain;
 struct sched_class {
 	const struct sched_class *next;
 
-	void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup);
+	void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup,
+			      bool head);
 	void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep);
 	void (*yield_task) (struct rq *rq);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 41e76d3..f47560f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1856,13 +1856,14 @@ static void update_avg(u64 *avg, u64 sample)
 	*avg += diff >> 3;
 }
 
-static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	if (wakeup)
 		p->se.start_runtime = p->se.sum_exec_runtime;
 
 	sched_info_queued(p);
-	p->sched_class->enqueue_task(rq, p, wakeup);
+	p->sched_class->enqueue_task(rq, p, wakeup, head);
 	p->se.on_rq = 1;
 }
 
@@ -1892,7 +1893,7 @@ static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
 	if (task_contributes_to_load(p))
 		rq->nr_uninterruptible--;
 
-	enqueue_task(rq, p, wakeup);
+	enqueue_task(rq, p, wakeup, false);
 	inc_nr_running(rq);
 }
 
@@ -4236,7 +4237,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	if (running)
 		p->sched_class->set_curr_task(rq);
 	if (on_rq) {
-		enqueue_task(rq, p, 0);
+		enqueue_task(rq, p, 0, false);
 
 		check_class_changed(rq, p, prev_class, oldprio, running);
 	}
@@ -4280,7 +4281,7 @@ void set_user_nice(struct task_struct *p, long nice)
 	delta = p->prio - old_prio;
 
 	if (on_rq) {
-		enqueue_task(rq, p, 0);
+		enqueue_task(rq, p, 0, false);
 		/*
 		 * If the task increased its priority or is running and
 		 * lowered its priority, then reschedule its CPU:
@@ -8230,7 +8231,7 @@ void sched_move_task(struct task_struct *tsk)
 	if (unlikely(running))
 		tsk->sched_class->set_curr_task(rq);
 	if (on_rq)
-		enqueue_task(rq, tsk, 0);
+		enqueue_task(rq, tsk, 0, false);
 
 	task_rq_unlock(rq, &flags);
 }
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 22231cc..0e7a7af 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1053,7 +1053,8 @@ static inline void hrtick_update(struct rq *rq)
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
-static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se = &p->se;
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 502bb61..38076da 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -878,7 +878,8 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 /*
  * Adding/removing a task to/from a priority array:
  */
-static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
 	struct sched_rt_entity *rt_se = &p->rt;
 

[patch 2/3] sched: Implement head queueing for sched_rt

[Thomas Gleixner]

[-- Attachment #1: sched-implement-head-queueing-for-rt.patch --]
[-- Type: text/plain, Size: 2719 bytes --]

The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Implement the functionality in sched_rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/sched_rt.c |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

Index: linux-2.6-tip/kernel/sched_rt.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched_rt.c
+++ linux-2.6-tip/kernel/sched_rt.c
@@ -194,7 +194,7 @@ static inline struct rt_rq *group_rt_rq(
 	return rt_se->my_q;
 }
 
-static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
 
 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
@@ -204,7 +204,7 @@ static void sched_rt_rq_enqueue(struct r
 
 	if (rt_rq->rt_nr_running) {
 		if (rt_se && !on_rt_rq(rt_se))
-			enqueue_rt_entity(rt_se);
+			enqueue_rt_entity(rt_se, false);
 		if (rt_rq->highest_prio.curr < curr->prio)
 			resched_task(curr);
 	}
@@ -803,7 +803,7 @@ void dec_rt_tasks(struct sched_rt_entity
 	dec_rt_group(rt_se, rt_rq);
 }
 
-static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
+static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 {
 	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 	struct rt_prio_array *array = &rt_rq->active;
@@ -819,7 +819,10 @@ static void __enqueue_rt_entity(struct s
 	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 		return;
 
-	list_add_tail(&rt_se->run_list, queue);
+	if (head)
+		list_add(&rt_se->run_list, queue);
+	else
+		list_add_tail(&rt_se->run_list, queue);
 	__set_bit(rt_se_prio(rt_se), array->bitmap);
 
 	inc_rt_tasks(rt_se, rt_rq);
@@ -856,11 +859,11 @@ static void dequeue_rt_stack(struct sche
 	}
 }
 
-static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 {
 	dequeue_rt_stack(rt_se);
 	for_each_sched_rt_entity(rt_se)
-		__enqueue_rt_entity(rt_se);
+		__enqueue_rt_entity(rt_se, head);
 }
 
 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
@@ -871,7 +874,7 @@ static void dequeue_rt_entity(struct sch
 		struct rt_rq *rt_rq = group_rt_rq(rt_se);
 
 		if (rt_rq && rt_rq->rt_nr_running)
-			__enqueue_rt_entity(rt_se);
+			__enqueue_rt_entity(rt_se, false);
 	}
 }
 
@@ -886,7 +889,7 @@ enqueue_task_rt(struct rq *rq, struct ta
 	if (wakeup)
 		rt_se->timeout = 0;
 
-	enqueue_rt_entity(rt_se);
+	enqueue_rt_entity(rt_se, head);
 
 	if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
 		enqueue_pushable_task(rq, p);

[tip:sched/core] sched: Implement head queueing for sched_rt

[tip-bot for Thomas Gleixner]

Commit-ID:  37dad3fce97f01e5149d69de0833d8452c0e862e
Gitweb:     http://git.kernel.org/tip/37dad3fce97f01e5149d69de0833d8452c0e862e
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 20 Jan 2010 20:59:01 +0000
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 22 Jan 2010 18:09:59 +0100

sched: Implement head queueing for sched_rt

The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Implement the functionality in sched_rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.772169931@linutronix.de>
---
 kernel/sched_rt.c |   19 +++++++++++--------
 1 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 38076da..ca49ceb 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -194,7 +194,7 @@ static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 	return rt_se->my_q;
 }
 
-static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
 
 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
@@ -204,7 +204,7 @@ static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 
 	if (rt_rq->rt_nr_running) {
 		if (rt_se && !on_rt_rq(rt_se))
-			enqueue_rt_entity(rt_se);
+			enqueue_rt_entity(rt_se, false);
 		if (rt_rq->highest_prio.curr < curr->prio)
 			resched_task(curr);
 	}
@@ -803,7 +803,7 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 	dec_rt_group(rt_se, rt_rq);
 }
 
-static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
+static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 {
 	struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 	struct rt_prio_array *array = &rt_rq->active;
@@ -819,7 +819,10 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
 	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 		return;
 
-	list_add_tail(&rt_se->run_list, queue);
+	if (head)
+		list_add(&rt_se->run_list, queue);
+	else
+		list_add_tail(&rt_se->run_list, queue);
 	__set_bit(rt_se_prio(rt_se), array->bitmap);
 
 	inc_rt_tasks(rt_se, rt_rq);
@@ -856,11 +859,11 @@ static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 	}
 }
 
-static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 {
 	dequeue_rt_stack(rt_se);
 	for_each_sched_rt_entity(rt_se)
-		__enqueue_rt_entity(rt_se);
+		__enqueue_rt_entity(rt_se, head);
 }
 
 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
@@ -871,7 +874,7 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 		struct rt_rq *rt_rq = group_rt_rq(rt_se);
 
 		if (rt_rq && rt_rq->rt_nr_running)
-			__enqueue_rt_entity(rt_se);
+			__enqueue_rt_entity(rt_se, false);
 	}
 }
 
@@ -886,7 +889,7 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 	if (wakeup)
 		rt_se->timeout = 0;
 
-	enqueue_rt_entity(rt_se);
+	enqueue_rt_entity(rt_se, head);
 
 	if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
 		enqueue_pushable_task(rq, p);

[patch 3/3] sched: Queue a deboosted task to the head of the RT priority queue

[Thomas Gleixner]

[-- Attachment #1: rtmutex-set-prio-fix-deboost-enqueueing.patch --]
[-- Type: text/plain, Size: 1436 bytes --]

rtmutex_set_prio() is used to implement priority inheritance for
futexes. When a task is deboosted it gets enqueued at the tail of its RT
priority list. This is violating the POSIX scheduling semantics:

rt priority list X contains two runnable tasks A and B

task A	 runs with priority X and holds mutex M
task C	 preempts A and is blocked on mutex M 
     	 -> task A is boosted to priority of task C (Y)
task A	 unlocks the mutex M and deboosts itself
     	 -> A is dequeued from rt priority list Y
	 -> A is enqueued to the tail of rt priority list X
task C	 schedules away
task B	 runs

This is wrong as task A did not schedule away and therefor violates
the POSIX scheduling semantics.

Enqueue the task to the head of the priority list instead. 

Reported-by: Mathias Weber <mathias.weber.mw1@roche.com>
Reported-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/sched.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6-tip/kernel/sched.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched.c
+++ linux-2.6-tip/kernel/sched.c
@@ -6066,7 +6066,7 @@ void rt_mutex_setprio(struct task_struct
 	if (running)
 		p->sched_class->set_curr_task(rq);
 	if (on_rq) {
-		enqueue_task(rq, p, 0, false);
+		enqueue_task(rq, p, 0, oldprio < prio);
 
 		check_class_changed(rq, p, prev_class, oldprio, running);
 	}

[tip:sched/core] sched: Queue a deboosted task to the head of the RT prio queue

[tip-bot for Thomas Gleixner]

Commit-ID:  60db48cacb9b253d5607a5ff206112a59cd09e34
Gitweb:     http://git.kernel.org/tip/60db48cacb9b253d5607a5ff206112a59cd09e34
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 20 Jan 2010 20:59:06 +0000
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 22 Jan 2010 18:09:59 +0100

sched: Queue a deboosted task to the head of the RT prio queue

rtmutex_set_prio() is used to implement priority inheritance for
futexes. When a task is deboosted it gets enqueued at the tail of its
RT priority list. This is violating the POSIX scheduling semantics:

rt priority list X contains two runnable tasks A and B

task A	 runs with priority X and holds mutex M
task C	 preempts A and is blocked on mutex M 
     	 -> task A is boosted to priority of task C (Y)
task A	 unlocks the mutex M and deboosts itself
     	 -> A is dequeued from rt priority list Y
	 -> A is enqueued to the tail of rt priority list X
task C	 schedules away
task B	 runs

This is wrong as task A did not schedule away and therefor violates
the POSIX scheduling semantics.

Enqueue the task to the head of the priority list instead. 

Reported-by: Mathias Weber <mathias.weber.mw1@roche.com>
Reported-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.809074113@linutronix.de>
---
 kernel/sched.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index f47560f..a56ead4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4237,7 +4237,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	if (running)
 		p->sched_class->set_curr_task(rq);
 	if (on_rq) {
-		enqueue_task(rq, p, 0, false);
+		enqueue_task(rq, p, 0, oldprio < prio);
 
 		check_class_changed(rq, p, prev_class, oldprio, running);
 	}

Re: [patch 0/3] sched: Make Priority Inheritance POSIX compliant

[Peter Zijlstra]

On Wed, 2010-01-20 at 20:58 +0000, Thomas Gleixner wrote:
> The current PI implementation violates POSIX scheduling semantics when
> a thread is deboosted. The following patch series adresses this.
> 
> Thanks and Kudos go to Mathias Weber and Carsten Emde for analysis,
> test cases and initial workaround patches.

These look fine to me,

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Re: [patch 0/3] sched: Make Priority Inheritance POSIX compliant

[John Kacur]

On Wed, Jan 20, 2010 at 10:06 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, 2010-01-20 at 20:58 +0000, Thomas Gleixner wrote:
>> The current PI implementation violates POSIX scheduling semantics when
>> a thread is deboosted. The following patch series adresses this.
>>
>> Thanks and Kudos go to Mathias Weber and Carsten Emde for analysis,
>> test cases and initial workaround patches.

Oh, that sounds good - would you like to share the test cases for our
rt-test suite?

>
> These look fine to me,
>
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
>
> --
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Re: [patch 0/3] sched: Make Priority Inheritance POSIX compliant

[Carsten Emde]

On 01/20/2010 09:58 PM, Thomas Gleixner wrote:
> The current PI implementation violates POSIX scheduling semantics when
> a thread is deboosted. The following patch series addresses this.

I can confirm that this patch series fixes the incorrect scheduling
behavior as observed in our test case.

Thanks, Thomas!

Tested-by: Carsten Emde <cbe@osadl.org>

RE: [patch 0/3] sched: Make Priority Inheritance POSIX compliant

[Weber, Mathias]

On 01/20/2010 09:58 PM, Thomas Gleixner wrote:
>The current PI implementation violates POSIX scheduling semantics when
>a thread is deboosted. The following patch series adresses this.

I did rerun the test case with this patches applied and I can confirm
that this fixes the incorrect scheduling behavior in our test case.

Thanks, Thomas and Carsten for your help.

Tested-by: Mathias Weber <mathias.weber.mw1@oche.com>