ALSA: snd_usb_caiaq: track submitted output urbs

The snd_usb_caiaq driver currently assumes that output urbs are serviced
in time and doesn't track when and whether they are given back by the
USB core. That usually works fine, but due to temporary limitations of
the XHCI stack, we faced that urbs were submitted more than once with
this approach.

As it's no good practice to fire and forget urbs anyway, this patch
introduces a proper bit mask to track which requests have been submitted
and given back.

That alone however doesn't make the driver work in case the host
controller is broken and doesn't give back urbs at all, and the output
stream will stop once all pre-allocated output urbs are consumed. But
it does prevent crashes of the controller stack in such cases.

See http://bugzilla.kernel.org/show_bug.cgi?id=40702 for more details.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Reported-and-tested-by: Matej Laitl <matej@laitl.cz>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/caiaq/audio.c b/sound/usb/caiaq/audio.c
index aa52b3e13bb5348c81f6e0b74cede4cd90960455..2cf87f5afed4e2fbc93cdcdf4d72277b8afae52f 100644 (file)
--- a/sound/usb/caiaq/audio.c
+++ b/sound/usb/caiaq/audio.c
@@ -139,8 +139,12 @@ static void stream_stop(struct snd_usb_caiaqdev *dev)
 
        for (i = 0; i < N_URBS; i++) {
                usb_kill_urb(dev->data_urbs_in[i]);
-               usb_kill_urb(dev->data_urbs_out[i]);
+
+               if (test_bit(i, &dev->outurb_active_mask))
+                       usb_kill_urb(dev->data_urbs_out[i]);
        }
+
+       dev->outurb_active_mask = 0;
 }
 
 static int snd_usb_caiaq_substream_open(struct snd_pcm_substream *substream)
@@ -612,8 +616,8 @@ static void read_completed(struct urb *urb)
 {
        struct snd_usb_caiaq_cb_info *info = urb->context;
        struct snd_usb_caiaqdev *dev;
-       struct urb *out;
-       int frame, len, send_it = 0, outframe = 0;
+       struct urb *out = NULL;
+       int i, frame, len, send_it = 0, outframe = 0;
        size_t offset = 0;
 
        if (urb->status || !info)
@@ -624,7 +628,17 @@ static void read_completed(struct urb *urb)
        if (!dev->streaming)
                return;
 
-       out = dev->data_urbs_out[info->index];
+       /* find an unused output urb that is unused */
+       for (i = 0; i < N_URBS; i++)
+               if (test_and_set_bit(i, &dev->outurb_active_mask) == 0) {
+                       out = dev->data_urbs_out[i];
+                       break;
+               }
+
+       if (!out) {
+               log("Unable to find an output urb to use\n");
+               goto requeue;
+       }
 
        /* read the recently received packet and send back one which has
         * the same layout */
@@ -655,8 +669,12 @@ static void read_completed(struct urb *urb)
                out->number_of_packets = outframe;
                out->transfer_flags = URB_ISO_ASAP;
                usb_submit_urb(out, GFP_ATOMIC);
+       } else {
+               struct snd_usb_caiaq_cb_info *oinfo = out->context;
+               clear_bit(oinfo->index, &dev->outurb_active_mask);
        }
 
+requeue:
        /* re-submit inbound urb */
        for (frame = 0; frame < FRAMES_PER_URB; frame++) {
                urb->iso_frame_desc[frame].offset = BYTES_PER_FRAME * frame;
@@ -678,6 +696,8 @@ static void write_completed(struct urb *urb)
                dev->output_running = 1;
                wake_up(&dev->prepare_wait_queue);
        }
+
+       clear_bit(info->index, &dev->outurb_active_mask);
 }
 
 static struct urb **alloc_urbs(struct snd_usb_caiaqdev *dev, int dir, int *ret)
@@ -829,6 +849,9 @@ int snd_usb_caiaq_audio_init(struct snd_usb_caiaqdev *dev)
        if (!dev->data_cb_info)
                return -ENOMEM;
 
+       dev->outurb_active_mask = 0;
+       BUILD_BUG_ON(N_URBS > (sizeof(dev->outurb_active_mask) * 8));
+
        for (i = 0; i < N_URBS; i++) {
                dev->data_cb_info[i].dev = dev;
                dev->data_cb_info[i].index = i;

diff --git a/sound/usb/caiaq/device.h b/sound/usb/caiaq/device.h
index b2b310194ffa4c27640ccdb624885500dd562ed5..3f9c6339ae90fa54dd41cad9920e8d60223ddcd6 100644 (file)
--- a/sound/usb/caiaq/device.h
+++ b/sound/usb/caiaq/device.h
@@ -96,6 +96,7 @@ struct snd_usb_caiaqdev {
        int input_panic, output_panic, warned;
        char *audio_in_buf, *audio_out_buf;
        unsigned int samplerates, bpp;
+       unsigned long outurb_active_mask;
 
        struct snd_pcm_substream *sub_playback[MAX_STREAMS];
        struct snd_pcm_substream *sub_capture[MAX_STREAMS];