ALSA: snd-usb: Fix URB cancellation at stream start

Commit e9ba389c5 ("ALSA: usb-audio: Fix scheduling-while-atomic bug in
PCM capture stream") fixed a scheduling-while-atomic bug that happened
when snd_usb_endpoint_start was called from the trigger callback, which
is an atmic context. However, the patch breaks the idea of the endpoints
reference counting, which is the reason why the driver has been
refactored lately.

Revert that commit and let snd_usb_endpoint_start() take care of the URB
cancellation again. As this function is called from both atomic and
non-atomic context, add a flag to denote whether the function may sleep.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: stable@kernel.org [3.5+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 5 insertions, 8 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 62ec808ed792..1546577ae458 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -212,7 +212,7 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
         }
 }
 
-static int start_endpoints(struct snd_usb_substream *subs)
+static int start_endpoints(struct snd_usb_substream *subs, int can_sleep)
 {
         int err;
 
@@ -225,7 +225,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
                 snd_printdd(KERN_DEBUG "Starting data EP @%p\n", ep);
 
                 ep->data_subs = subs;
-                err = snd_usb_endpoint_start(ep);
+                err = snd_usb_endpoint_start(ep, can_sleep);
                 if (err < 0) {
                         clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags);
                         return err;
@@ -239,7 +239,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
                 snd_printdd(KERN_DEBUG "Starting sync EP @%p\n", ep);
 
                 ep->sync_slave = subs->data_endpoint;
-                err = snd_usb_endpoint_start(ep);
+                err = snd_usb_endpoint_start(ep, can_sleep);
                 if (err < 0) {
                         clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
                         return err;
@@ -544,13 +544,10 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
         subs->last_frame_number = 0;
         runtime->delay = 0;
 
-        /* clear the pending deactivation on the target EPs */
-        deactivate_endpoints(subs);
-
         /* for playback, submit the URBs now; otherwise, the first hwptr_done
          * updates for all URBs would happen at the same time when starting */
         if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK)
-                return start_endpoints(subs);
+                return start_endpoints(subs, 1);
 
         return 0;
 }
@@ -1175,7 +1172,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
 
         switch (cmd) {
         case SNDRV_PCM_TRIGGER_START:
-                err = start_endpoints(subs);
+                err = start_endpoints(subs, 0);
                 if (err < 0)
                         return err;