[alsa-devel] [PATCH 2/2] ALSA: usb-audio: Fix races at disconnection

Takashi Iwai tiwai at suse.de
Fri Oct 12 16:34:52 CEST 2012


Close some races at disconnection of a USB audio device by adding the
chip->shutdown_mutex and chip->shutdown check at appropriate places.

The spots to put bandaids are:
- PCM prepare, hw_params and hw_free
- where the usb device is accessed for communication or get speed, in
 mixer.c and others; the device speed is now cached in subs->speed
 instead of accessing to chip->dev

The accesses in PCM open and close don't need the mutex protection
because these are already handled in the core PCM disconnection code.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/card.h   |  1 +
 sound/usb/mixer.c  | 45 +++++++++++++++++++++++++++++++--------------
 sound/usb/pcm.c    | 50 +++++++++++++++++++++++++++++++++-----------------
 sound/usb/proc.c   |  4 ++--
 sound/usb/stream.c |  1 +
 5 files changed, 68 insertions(+), 33 deletions(-)

diff --git a/sound/usb/card.h b/sound/usb/card.h
index afa4f9e..814cb35 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -126,6 +126,7 @@ struct snd_usb_substream {
 	struct snd_usb_endpoint *sync_endpoint;
 	unsigned long flags;
 	bool need_setup_ep;		/* (re)configure EP at prepare? */
+	unsigned int speed;		/* USB_SPEED_XXX */
 
 	u64 formats;			/* format bitmasks (all or'ed) */
 	unsigned int num_formats;		/* number of supported audio formats (list) */
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index fe56c9d..8cfc6b0 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -287,24 +287,29 @@ static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request, int v
 	unsigned char buf[2];
 	int val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
 	int timeout = 10;
-	int err;
+	int idx = 0, err;
 
 	err = snd_usb_autoresume(cval->mixer->chip);
 	if (err < 0)
 		return -EIO;
 	while (timeout-- > 0) {
+		mutex_lock(&chip->shutdown_mutex);
+		if (chip->shutdown)
+			break;
+		idx = snd_usb_ctrl_intf(chip) | (cval->id << 8);
 		if (snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), request,
 				    USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
-				    validx, snd_usb_ctrl_intf(chip) | (cval->id << 8),
-				    buf, val_len) >= val_len) {
+				    validx, idx, buf, val_len) >= val_len) {
 			*value_ret = convert_signed_value(cval, snd_usb_combine_bytes(buf, val_len));
+			mutex_unlock(&chip->shutdown_mutex);
 			snd_usb_autosuspend(cval->mixer->chip);
 			return 0;
 		}
+		mutex_unlock(&chip->shutdown_mutex);
 	}
 	snd_usb_autosuspend(cval->mixer->chip);
 	snd_printdd(KERN_ERR "cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
-		    request, validx, snd_usb_ctrl_intf(chip) | (cval->id << 8), cval->val_type);
+		    request, validx, idx, cval->val_type);
 	return -EINVAL;
 }
 
@@ -313,7 +318,7 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request, int v
 	struct snd_usb_audio *chip = cval->mixer->chip;
 	unsigned char buf[2 + 3*sizeof(__u16)]; /* enough space for one range */
 	unsigned char *val;
-	int ret, size;
+	int idx = 0, ret, size;
 	__u8 bRequest;
 
 	if (request == UAC_GET_CUR) {
@@ -330,16 +335,22 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request, int v
 	if (ret)
 		goto error;
 
-	ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
+	mutex_lock(&chip->shutdown_mutex);
+	if (chip->shutdown)
+		ret = -ENODEV;
+	else {
+		idx = snd_usb_ctrl_intf(chip) | (cval->id << 8);
+		ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
 			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
-			      validx, snd_usb_ctrl_intf(chip) | (cval->id << 8),
-			      buf, size);
+			      validx, idx, buf, size);
+	}
+	mutex_unlock(&chip->shutdown_mutex);
 	snd_usb_autosuspend(chip);
 
 	if (ret < 0) {
 error:
 		snd_printk(KERN_ERR "cannot get ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d\n",
-			   request, validx, snd_usb_ctrl_intf(chip) | (cval->id << 8), cval->val_type);
+			   request, validx, idx, cval->val_type);
 		return ret;
 	}
 
@@ -417,7 +428,7 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
 {
 	struct snd_usb_audio *chip = cval->mixer->chip;
 	unsigned char buf[2];
-	int val_len, err, timeout = 10;
+	int idx = 0, val_len, err, timeout = 10;
 
 	if (cval->mixer->protocol == UAC_VERSION_1) {
 		val_len = cval->val_type >= USB_MIXER_S16 ? 2 : 1;
@@ -440,18 +451,24 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
 	err = snd_usb_autoresume(chip);
 	if (err < 0)
 		return -EIO;
-	while (timeout-- > 0)
+	while (timeout-- > 0) {
+		mutex_lock(&chip->shutdown_mutex);
+		if (chip->shutdown)
+			break;
+		idx = snd_usb_ctrl_intf(chip) | (cval->id << 8);
 		if (snd_usb_ctl_msg(chip->dev,
 				    usb_sndctrlpipe(chip->dev, 0), request,
 				    USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
-				    validx, snd_usb_ctrl_intf(chip) | (cval->id << 8),
-				    buf, val_len) >= 0) {
+				    validx, idx, buf, val_len) >= 0) {
+			mutex_unlock(&chip->shutdown_mutex);
 			snd_usb_autosuspend(chip);
 			return 0;
 		}
+		mutex_unlock(&chip->shutdown_mutex);
+	}
 	snd_usb_autosuspend(chip);
 	snd_printdd(KERN_ERR "cannot set ctl value: req = %#x, wValue = %#x, wIndex = %#x, type = %d, data = %#x/%#x\n",
-		    request, validx, snd_usb_ctrl_intf(chip) | (cval->id << 8), cval->val_type, buf[0], buf[1]);
+		    request, validx, idx, cval->val_type, buf[0], buf[1]);
 	return -EINVAL;
 }
 
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 55e19e1..7d3a78a 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -71,6 +71,8 @@ static snd_pcm_uframes_t snd_usb_pcm_pointer(struct snd_pcm_substream *substream
 	unsigned int hwptr_done;
 
 	subs = (struct snd_usb_substream *)substream->runtime->private_data;
+	if (subs->stream->chip->shutdown)
+		return SNDRV_PCM_POS_XRUN;
 	spin_lock(&subs->lock);
 	hwptr_done = subs->hwptr_done;
 	substream->runtime->delay = snd_usb_pcm_delay(subs,
@@ -444,7 +446,6 @@ static int configure_endpoint(struct snd_usb_substream *subs)
 {
 	int ret;
 
-	mutex_lock(&subs->stream->chip->shutdown_mutex);
 	/* format changed */
 	stop_endpoints(subs, 0, 0, 0);
 	ret = snd_usb_endpoint_set_params(subs->data_endpoint,
@@ -455,7 +456,7 @@ static int configure_endpoint(struct snd_usb_substream *subs)
 					  subs->cur_audiofmt,
 					  subs->sync_endpoint);
 	if (ret < 0)
-		goto unlock;
+		return ret;
 
 	if (subs->sync_endpoint)
 		ret = snd_usb_endpoint_set_params(subs->data_endpoint,
@@ -465,9 +466,6 @@ static int configure_endpoint(struct snd_usb_substream *subs)
 						  subs->cur_rate,
 						  subs->cur_audiofmt,
 						  NULL);
-
-unlock:
-	mutex_unlock(&subs->stream->chip->shutdown_mutex);
 	return ret;
 }
 
@@ -505,7 +503,13 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
-	if ((ret = set_format(subs, fmt)) < 0)
+	mutex_lock(&subs->stream->chip->shutdown_mutex);
+	if (subs->stream->chip->shutdown)
+		ret = -ENODEV;
+	else
+		ret = set_format(subs, fmt);
+	mutex_unlock(&subs->stream->chip->shutdown_mutex);
+	if (ret < 0)
 		return ret;
 
 	subs->interface = fmt->iface;
@@ -528,8 +532,10 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 	subs->cur_rate = 0;
 	subs->period_bytes = 0;
 	mutex_lock(&subs->stream->chip->shutdown_mutex);
-	stop_endpoints(subs, 0, 1, 1);
-	deactivate_endpoints(subs);
+	if (!subs->stream->chip->shutdown) {
+		stop_endpoints(subs, 0, 1, 1);
+		deactivate_endpoints(subs);
+	}
 	mutex_unlock(&subs->stream->chip->shutdown_mutex);
 	return snd_pcm_lib_free_vmalloc_buffer(substream);
 }
@@ -552,12 +558,19 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 		return -ENXIO;
 	}
 
-	if (snd_BUG_ON(!subs->data_endpoint))
-		return -EIO;
+	mutex_lock(&subs->stream->chip->shutdown_mutex);
+	if (subs->stream->chip->shutdown) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+	if (snd_BUG_ON(!subs->data_endpoint)) {
+		ret = -EIO;
+		goto unlock;
+	}
 
 	ret = set_format(subs, subs->cur_audiofmt);
 	if (ret < 0)
-		return ret;
+		goto unlock;
 
 	iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
 	alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
@@ -567,12 +580,12 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 				       subs->cur_audiofmt,
 				       subs->cur_rate);
 	if (ret < 0)
-		return ret;
+		goto unlock;
 
 	if (subs->need_setup_ep) {
 		ret = configure_endpoint(subs);
 		if (ret < 0)
-			return ret;
+			goto unlock;
 		subs->need_setup_ep = false;
 	}
 
@@ -592,9 +605,11 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	/* 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, 1);
+		ret = start_endpoints(subs, 1);
 
-	return 0;
+ unlock:
+	mutex_unlock(&subs->stream->chip->shutdown_mutex);
+	return ret;
 }
 
 static struct snd_pcm_hardware snd_usb_hardware =
@@ -647,7 +662,7 @@ static int hw_check_valid_format(struct snd_usb_substream *subs,
 		return 0;
 	}
 	/* check whether the period time is >= the data packet interval */
-	if (snd_usb_get_speed(subs->dev) != USB_SPEED_FULL) {
+	if (subs->speed != USB_SPEED_FULL) {
 		ptime = 125 * (1 << fp->datainterval);
 		if (ptime > pt->max || (ptime == pt->max && pt->openmax)) {
 			hwc_debug("   > check: ptime %u > max %u\n", ptime, pt->max);
@@ -925,7 +940,8 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
 		return err;
 
 	param_period_time_if_needed = SNDRV_PCM_HW_PARAM_PERIOD_TIME;
-	if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
+	subs->speed = snd_usb_get_speed(subs->dev);
+	if (subs->speed == USB_SPEED_FULL)
 		/* full speed devices have fixed data packet interval */
 		ptmin = 1000;
 	if (ptmin == 1000)
diff --git a/sound/usb/proc.c b/sound/usb/proc.c
index ebc1a5b..d218f76 100644
--- a/sound/usb/proc.c
+++ b/sound/usb/proc.c
@@ -108,7 +108,7 @@ static void proc_dump_substream_formats(struct snd_usb_substream *subs, struct s
 			}
 			snd_iprintf(buffer, "\n");
 		}
-		if (snd_usb_get_speed(subs->dev) != USB_SPEED_FULL)
+		if (subs->speed != USB_SPEED_FULL)
 			snd_iprintf(buffer, "    Data packet interval: %d us\n",
 				    125 * (1 << fp->datainterval));
 		// snd_iprintf(buffer, "    Max Packet Size = %d\n", fp->maxpacksize);
@@ -124,7 +124,7 @@ static void proc_dump_ep_status(struct snd_usb_substream *subs,
 		return;
 	snd_iprintf(buffer, "    Packet Size = %d\n", ep->curpacksize);
 	snd_iprintf(buffer, "    Momentary freq = %u Hz (%#x.%04x)\n",
-		    snd_usb_get_speed(subs->dev) == USB_SPEED_FULL
+		    subs->speed == USB_SPEED_FULL
 		    ? get_full_speed_hz(ep->freqm)
 		    : get_high_speed_hz(ep->freqm),
 		    ep->freqm >> 16, ep->freqm & 0xffff);
diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index 083ed81..1de0c8c 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -90,6 +90,7 @@ static void snd_usb_init_substream(struct snd_usb_stream *as,
 	subs->direction = stream;
 	subs->dev = as->chip->dev;
 	subs->txfr_quirk = as->chip->txfr_quirk;
+	subs->speed = snd_usb_get_speed(subs->dev);
 
 	snd_usb_set_pcm_ops(as->pcm, stream);
 
-- 
1.7.12.2



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