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Date:	Thu, 17 Jul 2014 11:24:58 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Carsten Emde <C.Emde@...dl.org>,
	John Kacur <jkacur@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [ANNOUNCE] 3.12.24-rt38


Dear RT Folks,

I'm pleased to announce the 3.12.24-rt38 stable release.


You can get this release via the git tree at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

  branch: v3.12-rt
  Head SHA1: e0c7cbcada84aa70709673b0d0fba0ca5d11cb01


Or to build 3.12.24-rt38 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.12.tar.xz

  http://www.kernel.org/pub/linux/kernel/v3.x/patch-3.12.24.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/3.12/patch-3.12.24-rt38.patch.xz



You can also build from 3.12.24-rt37 by applying the incremental patch:

  http://www.kernel.org/pub/linux/kernel/projects/rt/3.12/incr/patch-3.12.24-rt37-rt38.patch.xz



Enjoy,

-- Steve


Changes from v3.12.24-rt37:

---

Steven Rostedt (1):
      sched: Do not clear PF_NO_SETAFFINITY flag in select_fallback_rq()

Steven Rostedt (Red Hat) (1):
      Linux 3.12.24-rt38

Thomas Gleixner (1):
      workqueue: Prevent deadlock/stall on RT

----
 kernel/sched/core.c | 13 +++++-------
 kernel/workqueue.c  | 61 +++++++++++++++++++++++++++++++++++++++++------------
 localversion-rt     |  2 +-
 3 files changed, 54 insertions(+), 22 deletions(-)
---------------------------
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f6f3b3d72578..5e741c96af15 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1289,12 +1289,6 @@ out:
 		}
 	}
 
-	/*
-	 * Clear PF_NO_SETAFFINITY, otherwise we wreckage
-	 * migrate_disable/enable. See optimization for
-	 * PF_NO_SETAFFINITY tasks there.
-	 */
-	p->flags &= ~PF_NO_SETAFFINITY;
 	return dest_cpu;
 }
 
@@ -2651,9 +2645,8 @@ need_resched:
 
 static inline void sched_submit_work(struct task_struct *tsk)
 {
-	if (!tsk->state || tsk_is_pi_blocked(tsk))
+	if (!tsk->state)
 		return;
-
 	/*
 	 * If a worker went to sleep, notify and ask workqueue whether
 	 * it wants to wake up a task to maintain concurrency.
@@ -2661,6 +2654,10 @@ static inline void sched_submit_work(struct task_struct *tsk)
 	if (tsk->flags & PF_WQ_WORKER)
 		wq_worker_sleeping(tsk);
 
+
+	if (tsk_is_pi_blocked(tsk))
+		return;
+
 	/*
 	 * If we are going to sleep and we have plugged IO queued,
 	 * make sure to submit it to avoid deadlocks.
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index be0ef50a2395..505b55b3c7ae 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -126,6 +126,11 @@ enum {
  *    cpu or grabbing pool->lock is enough for read access.  If
  *    POOL_DISASSOCIATED is set, it's identical to L.
  *
+ *    On RT we need the extra protection via rt_lock_idle_list() for
+ *    the list manipulations against read access from
+ *    wq_worker_sleeping(). All other places are nicely serialized via
+ *    pool->lock.
+ *
  * MG: pool->manager_mutex and pool->lock protected.  Writes require both
  *     locks.  Reads can happen under either lock.
  *
@@ -409,6 +414,31 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
 		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
 		else
 
+#ifdef CONFIG_PREEMPT_RT_BASE
+static inline void rt_lock_idle_list(struct worker_pool *pool)
+{
+	preempt_disable();
+}
+static inline void rt_unlock_idle_list(struct worker_pool *pool)
+{
+	preempt_enable();
+}
+static inline void sched_lock_idle_list(struct worker_pool *pool) { }
+static inline void sched_unlock_idle_list(struct worker_pool *pool) { }
+#else
+static inline void rt_lock_idle_list(struct worker_pool *pool) { }
+static inline void rt_unlock_idle_list(struct worker_pool *pool) { }
+static inline void sched_lock_idle_list(struct worker_pool *pool)
+{
+	spin_lock_irq(&pool->lock);
+}
+static inline void sched_unlock_idle_list(struct worker_pool *pool)
+{
+	spin_unlock_irq(&pool->lock);
+}
+#endif
+
+
 #ifdef CONFIG_DEBUG_OBJECTS_WORK
 
 static struct debug_obj_descr work_debug_descr;
@@ -801,10 +831,16 @@ static struct worker *first_worker(struct worker_pool *pool)
  */
 static void wake_up_worker(struct worker_pool *pool)
 {
-	struct worker *worker = first_worker(pool);
+	struct worker *worker;
+
+	rt_lock_idle_list(pool);
+
+	worker = first_worker(pool);
 
 	if (likely(worker))
 		wake_up_process(worker->task);
+
+	rt_unlock_idle_list(pool);
 }
 
 /**
@@ -832,7 +868,7 @@ void wq_worker_running(struct task_struct *task)
  */
 void wq_worker_sleeping(struct task_struct *task)
 {
-	struct worker *next, *worker = kthread_data(task);
+	struct worker *worker = kthread_data(task);
 	struct worker_pool *pool;
 
 	/*
@@ -849,25 +885,18 @@ void wq_worker_sleeping(struct task_struct *task)
 		return;
 
 	worker->sleeping = 1;
-	spin_lock_irq(&pool->lock);
+
 	/*
 	 * The counterpart of the following dec_and_test, implied mb,
 	 * worklist not empty test sequence is in insert_work().
 	 * Please read comment there.
-	 *
-	 * NOT_RUNNING is clear.  This means that we're bound to and
-	 * running on the local cpu w/ rq lock held and preemption
-	 * disabled, which in turn means that none else could be
-	 * manipulating idle_list, so dereferencing idle_list without pool
-	 * lock is safe.
 	 */
 	if (atomic_dec_and_test(&pool->nr_running) &&
 	    !list_empty(&pool->worklist)) {
-		next = first_worker(pool);
-		if (next)
-			wake_up_process(next->task);
+		sched_lock_idle_list(pool);
+		wake_up_worker(pool);
+		sched_unlock_idle_list(pool);
 	}
-	spin_unlock_irq(&pool->lock);
 }
 
 /**
@@ -1571,7 +1600,9 @@ static void worker_enter_idle(struct worker *worker)
 	worker->last_active = jiffies;
 
 	/* idle_list is LIFO */
+	rt_lock_idle_list(pool);
 	list_add(&worker->entry, &pool->idle_list);
+	rt_unlock_idle_list(pool);
 
 	if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
 		mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
@@ -1604,7 +1635,9 @@ static void worker_leave_idle(struct worker *worker)
 		return;
 	worker_clr_flags(worker, WORKER_IDLE);
 	pool->nr_idle--;
+	rt_lock_idle_list(pool);
 	list_del_init(&worker->entry);
+	rt_unlock_idle_list(pool);
 }
 
 /**
@@ -1849,7 +1882,9 @@ static void destroy_worker(struct worker *worker)
 	 */
 	get_task_struct(worker->task);
 
+	rt_lock_idle_list(pool);
 	list_del_init(&worker->entry);
+	rt_unlock_idle_list(pool);
 	worker->flags |= WORKER_DIE;
 
 	idr_remove(&pool->worker_idr, worker->id);
diff --git a/localversion-rt b/localversion-rt
index a3b2408c1da6..49bae8d6aa67 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt37
+-rt38
--
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