2 files changed, 58 insertions, 36 deletions

diff --git a/drivers/ieee1394/raw1394-private.h b/drivers/ieee1394/raw1394-private.h
index c93587b..c7731d1 100644
--- a/drivers/ieee1394/raw1394-private.h
+++ b/drivers/ieee1394/raw1394-private.h
@@ -29,9 +29,8 @@ struct file_info {
 
         struct list_head req_pending;
         struct list_head req_complete;
-        struct semaphore complete_sem;
         spinlock_t reqlists_lock;
-        wait_queue_head_t poll_wait_complete;
+        wait_queue_head_t wait_complete;
 
         struct list_head addr_list;
 
diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index 46c88e8..840b705 100644
--- a/drivers/ieee1394/raw1394.c
+++ b/drivers/ieee1394/raw1394.c
@@ -133,10 +133,9 @@ static void free_pending_request(struct pending_request *req)
 static void __queue_complete_req(struct pending_request *req)
 {
 	struct file_info *fi = req->file_info;
-	list_move_tail(&req->list, &fi->req_complete);
 
-	up(&fi->complete_sem);
-	wake_up_interruptible(&fi->poll_wait_complete);
+	list_move_tail(&req->list, &fi->req_complete);
+ 	wake_up(&fi->wait_complete);
 }
 
 static void queue_complete_req(struct pending_request *req)
@@ -464,13 +463,36 @@ raw1394_compat_read(const char __user *buf, struct raw1394_request *r)
 
 #endif
 
+/* get next completed request  (caller must hold fi->reqlists_lock) */
+static inline struct pending_request *__next_complete_req(struct file_info *fi)
+{
+	struct list_head *lh;
+	struct pending_request *req = NULL;
+
+	if (!list_empty(&fi->req_complete)) {
+		lh = fi->req_complete.next;
+		list_del(lh);
+		req = list_entry(lh, struct pending_request, list);
+	}
+	return req;
+}
+
+/* atomically get next completed request */
+static struct pending_request *next_complete_req(struct file_info *fi)
+{
+	unsigned long flags;
+	struct pending_request *req;
+
+	spin_lock_irqsave(&fi->reqlists_lock, flags);
+	req = __next_complete_req(fi);
+	spin_unlock_irqrestore(&fi->reqlists_lock, flags);
+	return req;
+}
 
 static ssize_t raw1394_read(struct file *file, char __user * buffer,
 			    size_t count, loff_t * offset_is_ignored)
 {
-	unsigned long flags;
 	struct file_info *fi = (struct file_info *)file->private_data;
-	struct list_head *lh;
 	struct pending_request *req;
 	ssize_t ret;
 
@@ -488,22 +510,21 @@ static ssize_t raw1394_read(struct file *file, char __user * buffer,
 	}
 
 	if (file->f_flags & O_NONBLOCK) {
-		if (down_trylock(&fi->complete_sem)) {
+		if (!(req = next_complete_req(fi)))
 			return -EAGAIN;
-		}
 	} else {
-		if (down_interruptible(&fi->complete_sem)) {
+		/*
+		 * NB: We call the macro wait_event_interruptible() with a
+		 * condition argument with side effect.  This is only possible
+		 * because the side effect does not occur until the condition
+		 * became true, and wait_event_interruptible() won't evaluate
+		 * the condition again after that.
+		 */
+		if (wait_event_interruptible(fi->wait_complete,
+					     (req = next_complete_req(fi))))
 			return -ERESTARTSYS;
-		}
 	}
 
-	spin_lock_irqsave(&fi->reqlists_lock, flags);
-	lh = fi->req_complete.next;
-	list_del(lh);
-	spin_unlock_irqrestore(&fi->reqlists_lock, flags);
-
-	req = list_entry(lh, struct pending_request, list);
-
 	if (req->req.length) {
 		if (copy_to_user(int2ptr(req->req.recvb), req->data,
 				 req->req.length)) {
@@ -2745,7 +2766,7 @@ static unsigned int raw1394_poll(struct file *file, poll_table * pt)
 	unsigned int mask = POLLOUT | POLLWRNORM;
 	unsigned long flags;
 
-	poll_wait(file, &fi->poll_wait_complete, pt);
+	poll_wait(file, &fi->wait_complete, pt);
 
 	spin_lock_irqsave(&fi->reqlists_lock, flags);
 	if (!list_empty(&fi->req_complete)) {
@@ -2770,9 +2791,8 @@ static int raw1394_open(struct inode *inode, struct file *file)
 	fi->state = opened;
 	INIT_LIST_HEAD(&fi->req_pending);
 	INIT_LIST_HEAD(&fi->req_complete);
-	sema_init(&fi->complete_sem, 0);
 	spin_lock_init(&fi->reqlists_lock);
-	init_waitqueue_head(&fi->poll_wait_complete);
+	init_waitqueue_head(&fi->wait_complete);
 	INIT_LIST_HEAD(&fi->addr_list);
 
 	file->private_data = fi;
@@ -2785,7 +2805,7 @@ static int raw1394_release(struct inode *inode, struct file *file)
 	struct file_info *fi = file->private_data;
 	struct list_head *lh;
 	struct pending_request *req;
-	int done = 0, i, fail = 0;
+	int i, fail;
 	int retval = 0;
 	struct list_head *entry;
 	struct arm_addr *addr = NULL;
@@ -2865,25 +2885,28 @@ static int raw1394_release(struct inode *inode, struct file *file)
 		       "error(s) occurred \n");
 	}
 
-	while (!done) {
+	for (;;) {
+		/* This locked section guarantees that neither
+		 * complete nor pending requests exist once i!=0 */
 		spin_lock_irqsave(&fi->reqlists_lock, flags);
-
-		while (!list_empty(&fi->req_complete)) {
-			lh = fi->req_complete.next;
-			list_del(lh);
-
-			req = list_entry(lh, struct pending_request, list);
-
+		while ((req = __next_complete_req(fi)))
 			free_pending_request(req);
-		}
-
-		if (list_empty(&fi->req_pending))
-			done = 1;
 
+		i = list_empty(&fi->req_pending);
 		spin_unlock_irqrestore(&fi->reqlists_lock, flags);
 
-		if (!done)
-			down_interruptible(&fi->complete_sem);
+		if (i)
+			break;
+		/*
+		 * Sleep until more requests can be freed.
+		 *
+		 * NB: We call the macro wait_event() with a condition argument
+		 * with side effect.  This is only possible because the side
+		 * effect does not occur until the condition became true, and
+		 * wait_event() won't evaluate the condition again after that.
+		 */
+		wait_event(fi->wait_complete, (req = next_complete_req(fi)));
+		free_pending_request(req);
 	}
 
 	/* Remove any sub-trees left by user space programs */