Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core locking changes from Ingo Molnar:
 "Main changes:

   - jump label asm preparatory work for PowerPC (Anton Blanchard)

   - rwsem optimizations and cleanups (Davidlohr Bueso)

   - mutex optimizations and cleanups (Jason Low)

   - futex fix (Oleg Nesterov)

   - remove broken atomicity checks from {READ,WRITE}_ONCE() (Peter
     Zijlstra)"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  powerpc, jump_label: Include linux/jump_label.h to get HAVE_JUMP_LABEL define
  jump_label: Allow jump labels to be used in assembly
  jump_label: Allow asm/jump_label.h to be included in assembly
  locking/mutex: Further simplify mutex_spin_on_owner()
  locking: Remove atomicy checks from {READ,WRITE}_ONCE
  locking/rtmutex: Rename argument in the rt_mutex_adjust_prio_chain() documentation as well
  locking/rwsem: Fix lock optimistic spinning when owner is not running
  locking: Remove ACCESS_ONCE() usage
  locking/rwsem: Check for active lock before bailing on spinning
  locking/rwsem: Avoid deceiving lock spinners
  locking/rwsem: Set lock ownership ASAP
  locking/rwsem: Document barrier need when waking tasks
  locking/futex: Check PF_KTHREAD rather than !p->mm to filter out kthreads
  locking/mutex: Refactor mutex_spin_on_owner()
  locking/mutex: In mutex_spin_on_owner(), return true when owner changes

1 files changed, 21 insertions, 30 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 94674e5919cb..4cccea6b8934 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -25,7 +25,7 @@
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
 #include <linux/debug_locks.h>
-#include "mcs_spinlock.h"
+#include <linux/osq_lock.h>
 
 /*
  * In the DEBUG case we are using the "NULL fastpath" for mutexes,
@@ -217,44 +217,35 @@ ww_mutex_set_context_slowpath(struct ww_mutex *lock,
 }
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
-static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
-{
-	if (lock->owner != owner)
-		return false;
-
-	/*
-	 * Ensure we emit the owner->on_cpu, dereference _after_ checking
-	 * lock->owner still matches owner, if that fails, owner might
-	 * point to free()d memory, if it still matches, the rcu_read_lock()
-	 * ensures the memory stays valid.
-	 */
-	barrier();
-
-	return owner->on_cpu;
-}
-
 /*
  * Look out! "owner" is an entirely speculative pointer
  * access and not reliable.
  */
 static noinline
-int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
 {
+	bool ret = true;
+
 	rcu_read_lock();
-	while (owner_running(lock, owner)) {
-		if (need_resched())
+	while (lock->owner == owner) {
+		/*
+		 * Ensure we emit the owner->on_cpu, dereference _after_
+		 * checking lock->owner still matches owner. If that fails,
+		 * owner might point to freed memory. If it still matches,
+		 * the rcu_read_lock() ensures the memory stays valid.
+		 */
+		barrier();
+
+		if (!owner->on_cpu || need_resched()) {
+			ret = false;
 			break;
+		}
 
 		cpu_relax_lowlatency();
 	}
 	rcu_read_unlock();
 
-	/*
-	 * We break out the loop above on need_resched() and when the
-	 * owner changed, which is a sign for heavy contention. Return
-	 * success only when lock->owner is NULL.
-	 */
-	return lock->owner == NULL;
+	return ret;
 }
 
 /*
@@ -269,7 +260,7 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
 		return 0;
 
 	rcu_read_lock();
-	owner = ACCESS_ONCE(lock->owner);
+	owner = READ_ONCE(lock->owner);
 	if (owner)
 		retval = owner->on_cpu;
 	rcu_read_unlock();
@@ -343,7 +334,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
 			 * As such, when deadlock detection needs to be
 			 * performed the optimistic spinning cannot be done.
 			 */
-			if (ACCESS_ONCE(ww->ctx))
+			if (READ_ONCE(ww->ctx))
 				break;
 		}
 
@@ -351,7 +342,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
 		 * If there's an owner, wait for it to either
 		 * release the lock or go to sleep.
 		 */
-		owner = ACCESS_ONCE(lock->owner);
+		owner = READ_ONCE(lock->owner);
 		if (owner && !mutex_spin_on_owner(lock, owner))
 			break;
 
@@ -490,7 +481,7 @@ static inline int __sched
 __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
 {
 	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
-	struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
+	struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
 
 	if (!hold_ctx)
 		return 0;