diff -urN 2.3.15-pre1/kernel/sched.c 2.3.15-pre1-wakeonesem1/kernel/sched.c
--- 2.3.15-pre1/kernel/sched.c	Fri Aug 20 17:43:24 1999
+++ 2.3.15-pre1-wakeonesem1/kernel/sched.c	Sat Aug 21 16:42:30 1999
@@ -863,6 +863,14 @@
  *
  * Either form may be used in conjunction with "up()".
  *
+ * NOTE NOTE:	The tasks that are sleeping on a semaphore will be
+ *		wakenup in a FIFO wake-one behaviour. For this reason
+ *		waking_non_zero_interruptible() _must_ first check if it
+ *		can grab the semaphore, and if so it must return successfully.
+ *		_Only_ if the seamphore is still busy it can then check if
+ *		there is a signal pending and fail _only_ in such case.
+ *		All architectures must enforce this rule to avoid deadlocking
+ *		with the wake-one wakeup.
  */
 
 #define DOWN_VAR				\
@@ -871,10 +879,7 @@
 	init_waitqueue_entry(&wait, tsk);
 
 #define DOWN_HEAD(task_state)						\
-									\
-									\
-	tsk->state = (task_state);					\
-	add_wait_queue(&sem->wait, &wait);				\
+	add_wait_queue_exclusive(&sem->wait, &wait);			\
 									\
 	/*								\
 	 * Ok, we're set up.  sem->count is known to be less than zero	\
@@ -891,10 +896,11 @@
 	 * Multiple waiters contend for the semaphore lock to see	\
 	 * who gets to gate through and who has to wait some more.	\
 	 */								\
-	for (;;) {
+	for (;;) {							\
+		tsk->state = (task_state);
 
-#define DOWN_TAIL(task_state)			\
-		tsk->state = (task_state);	\
+#define DOWN_TAIL()				\
+		schedule();			\
 	}					\
 	tsk->state = TASK_RUNNING;		\
 	remove_wait_queue(&sem->wait, &wait);
@@ -902,18 +908,19 @@
 void __down(struct semaphore * sem)
 {
 	DOWN_VAR
-	DOWN_HEAD(TASK_UNINTERRUPTIBLE)
+	DOWN_HEAD(TASK_UNINTERRUPTIBLE|TASK_EXCLUSIVE)
+
 	if (waking_non_zero(sem))
 		break;
-	schedule();
-	DOWN_TAIL(TASK_UNINTERRUPTIBLE)
+
+	DOWN_TAIL()
 }
 
 int __down_interruptible(struct semaphore * sem)
 {
 	int ret = 0;
 	DOWN_VAR
-	DOWN_HEAD(TASK_INTERRUPTIBLE)
+	DOWN_HEAD(TASK_INTERRUPTIBLE|TASK_EXCLUSIVE)
 
 	ret = waking_non_zero_interruptible(sem, tsk);
 	if (ret)
@@ -923,8 +930,8 @@
 			ret = 0;
 		break;
 	}
-	schedule();
-	DOWN_TAIL(TASK_INTERRUPTIBLE)
+
+	DOWN_TAIL()
 	return ret;
 }