ALSA: usb-audio: Refactoring endpoint URB deactivation

Minor code refactoring to consolidate the URB deactivation code in
endpoint.c.  A slight behavior change is that the error handling in
snd_usb_endpoint_start() leaves EP_FLAG_STOPPING now.  This should be
synced with the later PCM sync_stop callback.

Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Link: https://lore.kernel.org/r/20201123085347.19667-30-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 4d733b2..35c84c2 100644 (file)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -777,6 +777,9 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
        unsigned long end_time = jiffies + msecs_to_jiffies(1000);
        int alive;
 
+       if (!test_bit(EP_FLAG_STOPPING, &ep->flags))
+               return 0;
+
        do {
                alive = bitmap_weight(&ep->active_mask, ep->nurbs);
                if (!alive)
@@ -802,22 +805,31 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
  */
 void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
 {
-       if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
+       if (ep)
                wait_clear_urbs(ep);
 }
 
 /*
- * unlink active urbs.
+ * Stop and unlink active urbs.
+ *
+ * This function checks and clears EP_FLAG_RUNNING state.
+ * When @wait_sync is set, it waits until all pending URBs are killed.
  */
-static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)
+static int stop_and_unlink_urbs(struct snd_usb_endpoint *ep, bool force,
+                               bool wait_sync)
 {
        unsigned int i;
 
        if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */
                return -EBADFD;
 
-       clear_bit(EP_FLAG_RUNNING, &ep->flags);
+       if (atomic_read(&ep->running))
+               return -EBUSY;
+
+       if (!test_and_clear_bit(EP_FLAG_RUNNING, &ep->flags))
+               goto out;
 
+       set_bit(EP_FLAG_STOPPING, &ep->flags);
        INIT_LIST_HEAD(&ep->ready_playback_urbs);
        ep->next_packet_head = 0;
        ep->next_packet_queued = 0;
@@ -831,6 +843,9 @@ static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)
                }
        }
 
+ out:
+       if (wait_sync)
+               return wait_clear_urbs(ep);
        return 0;
 }
 
@@ -845,8 +860,7 @@ static void release_urbs(struct snd_usb_endpoint *ep, int force)
        snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL);
 
        /* stop urbs */
-       deactivate_urbs(ep, force);
-       wait_clear_urbs(ep);
+       stop_and_unlink_urbs(ep, force, true);
 
        for (i = 0; i < ep->nurbs; i++)
                release_urb_ctx(&ep->urb[i]);
@@ -1261,9 +1275,6 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
        if (atomic_inc_return(&ep->running) != 1)
                return 0;
 
-       /* just to be sure */
-       deactivate_urbs(ep, false);
-
        ep->active_mask = 0;
        ep->unlink_mask = 0;
        ep->phase = 0;
@@ -1317,11 +1328,7 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
        return 0;
 
 __error:
-       if (ep->sync_master)
-               WRITE_ONCE(ep->sync_master->sync_slave, NULL);
-       clear_bit(EP_FLAG_RUNNING, &ep->flags);
-       atomic_dec(&ep->running);
-       deactivate_urbs(ep, false);
+       snd_usb_endpoint_stop(ep);
        return -EPIPE;
 }
 
@@ -1354,10 +1361,8 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
        if (ep->sync_master)
                WRITE_ONCE(ep->sync_master->sync_slave, NULL);
 
-       if (!atomic_dec_return(&ep->running)) {
-               deactivate_urbs(ep, false);
-               set_bit(EP_FLAG_STOPPING, &ep->flags);
-       }
+       if (!atomic_dec_return(&ep->running))
+               stop_and_unlink_urbs(ep, false, false);
 }
 
 /**