Merge tag 'pm+acpi-fixes-3.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...

[pandora-kernel.git] / kernel / mutex.c

diff --git a/kernel/mutex.c b/kernel/mutex.c
index a52ee7b..6d647ae 100644 (file)
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -209,11 +209,13 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
  */
 static inline int mutex_can_spin_on_owner(struct mutex *lock)
 {
+       struct task_struct *owner;
        int retval = 1;
 
        rcu_read_lock();
-       if (lock->owner)
-               retval = lock->owner->on_cpu;
+       owner = ACCESS_ONCE(lock->owner);
+       if (owner)
+               retval = owner->on_cpu;
        rcu_read_unlock();
        /*
         * if lock->owner is not set, the mutex owner may have just acquired
@@ -461,7 +463,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                         * performed the optimistic spinning cannot be done.
                         */
                        if (ACCESS_ONCE(ww->ctx))
-                               break;
+                               goto slowpath;
                }
 
                /*
@@ -472,7 +474,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                owner = ACCESS_ONCE(lock->owner);
                if (owner && !mutex_spin_on_owner(lock, owner)) {
                        mspin_unlock(MLOCK(lock), &node);
-                       break;
+                       goto slowpath;
                }
 
                if ((atomic_read(&lock->count) == 1) &&
@@ -499,7 +501,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                 * the owner complete.
                 */
                if (!owner && (need_resched() || rt_task(task)))
-                       break;
+                       goto slowpath;
 
                /*
                 * The cpu_relax() call is a compiler barrier which forces
@@ -513,6 +515,10 @@ slowpath:
 #endif
        spin_lock_mutex(&lock->wait_lock, flags);
 
+       /* once more, can we acquire the lock? */
+       if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1))
+               goto skip_wait;
+
        debug_mutex_lock_common(lock, &waiter);
        debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
 
@@ -520,9 +526,6 @@ slowpath:
        list_add_tail(&waiter.list, &lock->wait_list);
        waiter.task = task;
 
-       if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1))
-               goto done;
-
        lock_contended(&lock->dep_map, ip);
 
        for (;;) {
@@ -536,7 +539,7 @@ slowpath:
                 * other waiters:
                 */
                if (MUTEX_SHOW_NO_WAITER(lock) &&
-                  (atomic_xchg(&lock->count, -1) == 1))
+                   (atomic_xchg(&lock->count, -1) == 1))
                        break;
 
                /*
@@ -561,24 +564,25 @@ slowpath:
                schedule_preempt_disabled();
                spin_lock_mutex(&lock->wait_lock, flags);
        }
+       mutex_remove_waiter(lock, &waiter, current_thread_info());
+       /* set it to 0 if there are no waiters left: */
+       if (likely(list_empty(&lock->wait_list)))
+               atomic_set(&lock->count, 0);
+       debug_mutex_free_waiter(&waiter);
 
-done:
+skip_wait:
+       /* got the lock - cleanup and rejoice! */
        lock_acquired(&lock->dep_map, ip);
-       /* got the lock - rejoice! */
-       mutex_remove_waiter(lock, &waiter, current_thread_info());
        mutex_set_owner(lock);
 
        if (!__builtin_constant_p(ww_ctx == NULL)) {
-               struct ww_mutex *ww = container_of(lock,
-                                                     struct ww_mutex,
-                                                     base);
+               struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
                struct mutex_waiter *cur;
 
                /*
                 * This branch gets optimized out for the common case,
                 * and is only important for ww_mutex_lock.
                 */
-
                ww_mutex_lock_acquired(ww, ww_ctx);
                ww->ctx = ww_ctx;
 
@@ -592,15 +596,8 @@ done:
                }
        }
 
-       /* set it to 0 if there are no waiters left: */
-       if (likely(list_empty(&lock->wait_list)))
-               atomic_set(&lock->count, 0);
-
        spin_unlock_mutex(&lock->wait_lock, flags);
-
-       debug_mutex_free_waiter(&waiter);
        preempt_enable();
-
        return 0;
 
 err: