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authorIoan-Adrian Ratiu <adi@adirat.com>2017-01-05 00:37:46 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-12 11:39:05 +0100
commitbe4e3aec56679ecf0c7d4130c976c838a4855ef8 (patch)
tree201695f6a2f2df92ba90c56016acbb60ebd6588a /sound
parent5b2c3cafcafc38a9cdf789d7d3a515eae88bdb3b (diff)
downloadlinux-aarch64-be4e3aec56679ecf0c7d4130c976c838a4855ef8.tar.gz
ALSA: usb-audio: Fix irq/process data synchronization
commit 1d0f953086f090a022f2c0e1448300c15372db46 upstream. Commit 16200948d83 ("ALSA: usb-audio: Fix race at stopping the stream") was incomplete causing another more severe kernel panic, so it got reverted. This fixes both the original problem and its fallout kernel race/crash. The original fix is to move the endpoint member NULL clearing logic inside wait_clear_urbs() so the irq triggering the urb completion doesn't call retire_capture/playback_urb() after the NULL clearing and generate a panic. However this creates a new race between snd_usb_endpoint_start()'s call to wait_clear_urbs() and the irq urb completion handler which again calls retire_capture/playback_urb() leading to a new NULL dereference. We keep the EP deactivation code in snd_usb_endpoint_start() because removing it will break the EP reference counting (see [1] [2] for info), however we don't need the "can_sleep" mechanism anymore because a new function was introduced (snd_usb_endpoint_sync_pending_stop()) which synchronizes pending stops and gets called inside the pcm prepare callback. It also makes sense to remove can_sleep because it was also removed from deactivate_urbs() signature in [3] so we benefit from more simplification. [1] commit 015618b90 ("ALSA: snd-usb: Fix URB cancellation at stream start") [2] commit e9ba389c5 ("ALSA: usb-audio: Fix scheduling-while-atomic bug in PCM capture stream") [3] commit ccc1696d5 ("ALSA: usb-audio: simplify endpoint deactivation code") Fixes: f8114f8583bb ("Revert "ALSA: usb-audio: Fix race at stopping the stream"") Signed-off-by: Ioan-Adrian Ratiu <adi@adirat.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
-rw-r--r--sound/usb/endpoint.c17
-rw-r--r--sound/usb/endpoint.h2
-rw-r--r--sound/usb/pcm.c10
3 files changed, 13 insertions, 16 deletions
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index c470251cea4b..c5251aaad844 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -534,6 +534,11 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
alive, ep->ep_num);
clear_bit(EP_FLAG_STOPPING, &ep->flags);
+ ep->data_subs = NULL;
+ ep->sync_slave = NULL;
+ ep->retire_data_urb = NULL;
+ ep->prepare_data_urb = NULL;
+
return 0;
}
@@ -898,9 +903,7 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
/**
* snd_usb_endpoint_start: start an snd_usb_endpoint
*
- * @ep: the endpoint to start
- * @can_sleep: flag indicating whether the operation is executed in
- * non-atomic context
+ * @ep: the endpoint to start
*
* A call to this function will increment the use count of the endpoint.
* In case it is not already running, the URBs for this endpoint will be
@@ -910,7 +913,7 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
*
* Returns an error if the URB submission failed, 0 in all other cases.
*/
-int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep)
+int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
{
int err;
unsigned int i;
@@ -924,8 +927,6 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep)
/* just to be sure */
deactivate_urbs(ep, false);
- if (can_sleep)
- wait_clear_urbs(ep);
ep->active_mask = 0;
ep->unlink_mask = 0;
@@ -1006,10 +1007,6 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
if (--ep->use_count == 0) {
deactivate_urbs(ep, false);
- ep->data_subs = NULL;
- ep->sync_slave = NULL;
- ep->retire_data_urb = NULL;
- ep->prepare_data_urb = NULL;
set_bit(EP_FLAG_STOPPING, &ep->flags);
}
}
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index 6428392d8f62..584f295d7c77 100644
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -18,7 +18,7 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
struct audioformat *fmt,
struct snd_usb_endpoint *sync_ep);
-int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep);
+int snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep);
void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 44d178ee9177..48afae053c56 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -218,7 +218,7 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
}
}
-static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
+static int start_endpoints(struct snd_usb_substream *subs)
{
int err;
@@ -231,7 +231,7 @@ static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
dev_dbg(&subs->dev->dev, "Starting data EP @%p\n", ep);
ep->data_subs = subs;
- err = snd_usb_endpoint_start(ep, can_sleep);
+ err = snd_usb_endpoint_start(ep);
if (err < 0) {
clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags);
return err;
@@ -260,7 +260,7 @@ static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
dev_dbg(&subs->dev->dev, "Starting sync EP @%p\n", ep);
ep->sync_slave = subs->data_endpoint;
- err = snd_usb_endpoint_start(ep, can_sleep);
+ err = snd_usb_endpoint_start(ep);
if (err < 0) {
clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
return err;
@@ -839,7 +839,7 @@ 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)
- ret = start_endpoints(subs, true);
+ ret = start_endpoints(subs);
unlock:
snd_usb_unlock_shutdown(subs->stream->chip);
@@ -1655,7 +1655,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
switch (cmd) {
case SNDRV_PCM_TRIGGER_START:
- err = start_endpoints(subs, false);
+ err = start_endpoints(subs);
if (err < 0)
return err;