ALSA: usb-audio: Fix crash at re-preparing the PCM stream

There are bug reports of a crash with USB-audio devices when PCM
prepare is performed immediately after the stream is stopped via
trigger callback.  It turned out that the problem is that we don't
wait until all URBs are killed.

This patch adds a new function to synchronize the pending stop
operation on an endpoint, and calls in the prepare callback for
avoiding the crash above.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=49181

Reported-and-tested-by: Artem S. Tashkinov <t.artem@lycos.com>
Cc: <stable@vger.kernel.org> [v3.6]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 7f78c6d782b079d621d007f7c757e7cfd93587c7..34de6f2faf6120b492eb65208b9c9805aafe44e3 100644 (file)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -35,6 +35,7 @@
 
 #define EP_FLAG_ACTIVATED      0
 #define EP_FLAG_RUNNING                1
+#define EP_FLAG_STOPPING       2
 
 /*
  * snd_usb_endpoint is a model that abstracts everything related to an
@@ -502,10 +503,20 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
        if (alive)
                snd_printk(KERN_ERR "timeout: still %d active urbs on EP #%x\n",
                                        alive, ep->ep_num);
+       clear_bit(EP_FLAG_STOPPING, &ep->flags);
 
        return 0;
 }
 
+/* sync the pending stop operation;
+ * this function itself doesn't trigger the stop operation
+ */
+void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
+{
+       if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
+               wait_clear_urbs(ep);
+}
+
 /*
  * unlink active urbs.
  */
@@ -918,6 +929,8 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
 
                if (wait)
                        wait_clear_urbs(ep);
+               else
+                       set_bit(EP_FLAG_STOPPING, &ep->flags);
        }
 }
 

diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index 6376ccf10fd470688daf103b37ff74bcf67af3ea..3d4c9705041ff5074c609dd2bfb303781a523c4e 100644 (file)
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -19,6 +19,7 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
 int  snd_usb_endpoint_start(struct snd_usb_endpoint *ep, int can_sleep);
 void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
                           int force, int can_sleep, int wait);
+void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
 int  snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
 int  snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
 void snd_usb_endpoint_free(struct list_head *head);

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 37428f74dbb69f90ae5e9cc580f3d2a9f81811e8..5c12a3fe8c3e8dfae0af6388b9ee3ea8c6c16047 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -568,6 +568,9 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
                goto unlock;
        }
 
+       snd_usb_endpoint_sync_pending_stop(subs->sync_endpoint);
+       snd_usb_endpoint_sync_pending_stop(subs->data_endpoint);
+
        ret = set_format(subs, subs->cur_audiofmt);
        if (ret < 0)
                goto unlock;