ALSA: usb-audio: Fix scheduling-while-atomic bug in PCM capture stream

A PCM capture stream on usb-audio causes a scheduling-while-atomic
BUG, as reported in the bugzilla entry below.  It's because
snd_usb_endpoint_start() is called at first at trigger START for a
capture stream, and this function contains the left-over EP
deactivation codes.  The problem doesn't happen for a playback stream
because the function is called at PCM prepare time, which can sleep.

This patch fixes the BUG by moving the EP deactivation code into the
PCM prepare callback.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=46011
Cc: <stable@vger.kernel.org> [v3.5+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 0f647d22cb4ac7bccffe25311011255cf0b33104..c411812026884408afd74f1e580f2e87bbe747fc 100644 (file)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -821,10 +821,6 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
        if (++ep->use_count != 1)
                return 0;
 
-       /* just to be sure */
-       deactivate_urbs(ep, 0, 1);
-       wait_clear_urbs(ep);
-
        ep->active_mask = 0;
        ep->unlink_mask = 0;
        ep->phase = 0;

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index a1298f379428280045bf661f89e5fa59bb0acb48..62ec808ed792503e789ea26eb74837998623915e 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -544,6 +544,9 @@ 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)