[ANNOUNCE] v5.14-rc3-rt2

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

Dear RT folks!

I'm pleased to announce the v5.14-rc3-rt2 patch set. 

Changes since v5.14-rc3-rt1:

  - To cope with SLUB based hackbench regression adaptive spinning has
    been introduced for all rtmutex based locks. This improves the
    hackbench time significantly.

Known issues
     - netconsole triggers WARN.

     - The "Memory controller" (CONFIG_MEMCG) has been disabled.

The delta patch against v5.14-rc3-rt1 is appended below and can be found here:
 
     https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.14/incr/patch-5.14-rc3-rt1-rt2.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v5.14-rc3-rt2

The RT patch against v5.14-rc3 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.14/older/patch-5.14-rc3-rt2.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.14/older/patches-5.14-rc3-rt2.tar.xz

Sebastian


diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 58762a3970ed7..e347bbc12641d 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1277,6 +1277,43 @@ static __always_inline void __rt_mutex_unlock(struct rt_mutex_base *lock)
 	rt_mutex_slowunlock(lock);
 }
 
+#ifdef CONFIG_SMP
+/*
+ * Note that owner is a speculative pointer and dereferencing relies
+ * on rcu_read_lock() and the check against the lock owner.
+ */
+static bool rtmutex_adaptive_spinwait(struct rt_mutex_base *lock,
+				     struct task_struct *owner)
+{
+	bool res = true;
+
+	rcu_read_lock();
+	for (;;) {
+		/* Owner changed. Trylock again */
+		if (owner != rt_mutex_owner(lock))
+			break;
+		/*
+		 * Ensure that owner->on_cpu is dereferenced _after_
+		 * checking the above to be valid.
+		 */
+		barrier();
+		if (!owner->on_cpu) {
+			res = false;
+			break;
+		}
+		cpu_relax();
+	}
+	rcu_read_unlock();
+	return res;
+}
+#else
+static bool rtmutex_adaptive_spinwait(struct rt_mutex_base *lock,
+				     struct task_struct *owner)
+{
+	return false;
+}
+#endif
+
 #ifdef RT_MUTEX_BUILD_MUTEX
 /*
  * Functions required for:
@@ -1361,6 +1398,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
 					   struct rt_mutex_waiter *waiter)
 {
 	struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex);
+	struct task_struct *owner;
 	int ret = 0;
 
 	for (;;) {
@@ -1383,9 +1421,14 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
 				break;
 		}
 
+		if (waiter == rt_mutex_top_waiter(lock))
+			owner = rt_mutex_owner(lock);
+		else
+			owner = NULL;
 		raw_spin_unlock_irq(&lock->wait_lock);
 
-		schedule();
+		if (!owner || !rtmutex_adaptive_spinwait(lock, owner))
+			schedule();
 
 		raw_spin_lock_irq(&lock->wait_lock);
 		set_current_state(state);
@@ -1534,43 +1577,6 @@ static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
  * Functions required for spin/rw_lock substitution on RT kernels
  */
 
-#ifdef CONFIG_SMP
-/*
- * Note that owner is a speculative pointer and dereferencing relies
- * on rcu_read_lock() and the check against the lock owner.
- */
-static bool rtlock_adaptive_spinwait(struct rt_mutex_base *lock,
-				     struct task_struct *owner)
-{
-	bool res = true;
-
-	rcu_read_lock();
-	for (;;) {
-		/* Owner changed. Trylock again */
-		if (owner != rt_mutex_owner(lock))
-			break;
-		/*
-		 * Ensure that owner->on_cpu is dereferenced _after_
-		 * checking the above to be valid.
-		 */
-		barrier();
-		if (!owner->on_cpu) {
-			res = false;
-			break;
-		}
-		cpu_relax();
-	}
-	rcu_read_unlock();
-	return res;
-}
-#else
-static bool rtlock_adaptive_spinwait(struct rt_mutex_base *lock,
-				     struct task_struct *owner)
-{
-	return false;
-}
-#endif
-
 /**
  * rtlock_slowlock_locked - Slow path lock acquisition for RT locks
  * @lock:	The underlying rt mutex
@@ -1603,7 +1609,7 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock)
 			owner = NULL;
 		raw_spin_unlock_irq(&lock->wait_lock);
 
-		if (!owner || !rtlock_adaptive_spinwait(lock, owner))
+		if (!owner || !rtmutex_adaptive_spinwait(lock, owner))
 			schedule_rtlock();
 
 		raw_spin_lock_irq(&lock->wait_lock);
diff --git a/localversion-rt b/localversion-rt
index 6f206be67cd28..c3054d08a1129 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt1
+-rt2