*
* This function is similar to (but not equivalent to) down().
*/
-void inline __sched mutex_lock(struct mutex *lock)
+void __sched mutex_lock(struct mutex *lock)
{
might_sleep();
/*
preempt_disable();
mutex_acquire(&lock->dep_map, subclass, 0, ip);
-#if defined(CONFIG_SMP) && !defined(CONFIG_DEBUG_MUTEXES)
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
* Optimistic spinning.
*
struct thread_info *owner;
/*
- * If there are pending waiters, join them.
+ * If we own the BKL, then don't spin. The owner of
+ * the mutex might be waiting on us to release the BKL.
*/
- if (!list_empty(&lock->wait_list))
+ if (unlikely(current->lock_depth >= 0))
break;
/*
if (owner && !mutex_spin_on_owner(lock, owner))
break;
+ if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
+ lock_acquired(&lock->dep_map, ip);
+ mutex_set_owner(lock);
+ preempt_enable();
+ return 0;
+ }
+
/*
* When there's no owner, we might have preempted between the
* owner acquiring the lock and setting the owner field. If
if (!owner && (need_resched() || rt_task(task)))
break;
- if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
- lock_acquired(&lock->dep_map, ip);
- mutex_set_owner(lock);
- preempt_enable();
- return 0;
- }
-
/*
* The cpu_relax() call is a compiler barrier which forces
* everything in this loop to be re-loaded. We don't need
/* didnt get the lock, go to sleep: */
spin_unlock_mutex(&lock->wait_lock, flags);
- __schedule();
+ preempt_enable_no_resched();
+ schedule();
+ preempt_disable();
spin_lock_mutex(&lock->wait_lock, flags);
}
return ret;
}
-
EXPORT_SYMBOL(mutex_trylock);
+
+/**
+ * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
+ * @cnt: the atomic which we are to dec
+ * @lock: the mutex to return holding if we dec to 0
+ *
+ * return true and hold lock if we dec to 0, return false otherwise
+ */
+int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
+{
+ /* dec if we can't possibly hit 0 */
+ if (atomic_add_unless(cnt, -1, 1))
+ return 0;
+ /* we might hit 0, so take the lock */
+ mutex_lock(lock);
+ if (!atomic_dec_and_test(cnt)) {
+ /* when we actually did the dec, we didn't hit 0 */
+ mutex_unlock(lock);
+ return 0;
+ }
+ /* we hit 0, and we hold the lock */
+ return 1;
+}
+EXPORT_SYMBOL(atomic_dec_and_mutex_lock);