1 files changed, 52 insertions, 19 deletions

diff --git a/sound/firewire/fireworks/fireworks_hwdep.c b/sound/firewire/fireworks/fireworks_hwdep.c
index 33df8655fe81..2e1d9a23920c 100644
--- a/sound/firewire/fireworks/fireworks_hwdep.c
+++ b/sound/firewire/fireworks/fireworks_hwdep.c
@@ -25,6 +25,7 @@ hwdep_read_resp_buf(struct snd_efw *efw, char __user *buf, long remained,
 {
 	unsigned int length, till_end, type;
 	struct snd_efw_transaction *t;
+	u8 *pull_ptr;
 	long count = 0;
 
 	if (remained < sizeof(type) + sizeof(struct snd_efw_transaction))
@@ -38,8 +39,17 @@ hwdep_read_resp_buf(struct snd_efw *efw, char __user *buf, long remained,
 	buf += sizeof(type);
 
 	/* write into buffer as many responses as possible */
-	while (efw->resp_queues > 0) {
-		t = (struct snd_efw_transaction *)(efw->pull_ptr);
+	spin_lock_irq(&efw->lock);
+
+	/*
+	 * When another task reaches here during this task's access to user
+	 * space, it picks up current position in buffer and can read the same
+	 * series of responses.
+	 */
+	pull_ptr = efw->pull_ptr;
+
+	while (efw->push_ptr != pull_ptr) {
+		t = (struct snd_efw_transaction *)(pull_ptr);
 		length = be32_to_cpu(t->length) * sizeof(__be32);
 
 		/* confirm enough space for this response */
@@ -49,26 +59,39 @@ hwdep_read_resp_buf(struct snd_efw *efw, char __user *buf, long remained,
 		/* copy from ring buffer to user buffer */
 		while (length > 0) {
 			till_end = snd_efw_resp_buf_size -
-				(unsigned int)(efw->pull_ptr - efw->resp_buf);
+				(unsigned int)(pull_ptr - efw->resp_buf);
 			till_end = min_t(unsigned int, length, till_end);
 
-			if (copy_to_user(buf, efw->pull_ptr, till_end))
+			spin_unlock_irq(&efw->lock);
+
+			if (copy_to_user(buf, pull_ptr, till_end))
 				return -EFAULT;
 
-			efw->pull_ptr += till_end;
-			if (efw->pull_ptr >= efw->resp_buf +
-					     snd_efw_resp_buf_size)
-				efw->pull_ptr -= snd_efw_resp_buf_size;
+			spin_lock_irq(&efw->lock);
+
+			pull_ptr += till_end;
+			if (pull_ptr >= efw->resp_buf + snd_efw_resp_buf_size)
+				pull_ptr -= snd_efw_resp_buf_size;
 
 			length -= till_end;
 			buf += till_end;
 			count += till_end;
 			remained -= till_end;
 		}
-
-		efw->resp_queues--;
 	}
 
+	/*
+	 * All of tasks can read from the buffer nearly simultaneously, but the
+	 * last position for each task is different depending on the length of
+	 * given buffer. Here, for simplicity, a position of buffer is set by
+	 * the latest task. It's better for a listening application to allow one
+	 * thread to read from the buffer. Unless, each task can read different
+	 * sequence of responses depending on variation of buffer length.
+	 */
+	efw->pull_ptr = pull_ptr;
+
+	spin_unlock_irq(&efw->lock);
+
 	return count;
 }
 
@@ -76,14 +99,17 @@ static long
 hwdep_read_locked(struct snd_efw *efw, char __user *buf, long count,
 		  loff_t *offset)
 {
-	union snd_firewire_event event;
+	union snd_firewire_event event = {
+		.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
+	};
 
-	memset(&event, 0, sizeof(event));
+	spin_lock_irq(&efw->lock);
 
-	event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
 	event.lock_status.status = (efw->dev_lock_count > 0);
 	efw->dev_lock_changed = false;
 
+	spin_unlock_irq(&efw->lock);
+
 	count = min_t(long, count, sizeof(event.lock_status));
 
 	if (copy_to_user(buf, &event, count))
@@ -98,10 +124,15 @@ hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 {
 	struct snd_efw *efw = hwdep->private_data;
 	DEFINE_WAIT(wait);
+	bool dev_lock_changed;
+	bool queued;
 
 	spin_lock_irq(&efw->lock);
 
-	while ((!efw->dev_lock_changed) && (efw->resp_queues == 0)) {
+	dev_lock_changed = efw->dev_lock_changed;
+	queued = efw->push_ptr != efw->pull_ptr;
+
+	while (!dev_lock_changed && !queued) {
 		prepare_to_wait(&efw->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&efw->lock);
 		schedule();
@@ -109,15 +140,17 @@ hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 		spin_lock_irq(&efw->lock);
+		dev_lock_changed = efw->dev_lock_changed;
+		queued = efw->push_ptr != efw->pull_ptr;
 	}
 
-	if (efw->dev_lock_changed)
+	spin_unlock_irq(&efw->lock);
+
+	if (dev_lock_changed)
 		count = hwdep_read_locked(efw, buf, count, offset);
-	else if (efw->resp_queues > 0)
+	else if (queued)
 		count = hwdep_read_resp_buf(efw, buf, count, offset);
 
-	spin_unlock_irq(&efw->lock);
-
 	return count;
 }
 
@@ -160,7 +193,7 @@ hwdep_poll(struct snd_hwdep *hwdep, struct file *file, poll_table *wait)
 	poll_wait(file, &efw->hwdep_wait, wait);
 
 	spin_lock_irq(&efw->lock);
-	if (efw->dev_lock_changed || (efw->resp_queues > 0))
+	if (efw->dev_lock_changed || efw->pull_ptr != efw->push_ptr)
 		events = POLLIN | POLLRDNORM;
 	else
 		events = 0;