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| author | Ioan-Adrian Ratiu <adi@adirat.com> | 2017-01-05 01:37:46 +0300 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2017-01-05 09:35:00 +0300 |
| commit | 1d0f953086f090a022f2c0e1448300c15372db46 (patch) | |
| tree | 96e89154873d3b08b73e18d717e33631cb050f67 /sound/usb/endpoint.c | |
| parent | c7efff9284dfde95a11aaa811c9d8ec8167f0f6e (diff) | |
| download | linux-1d0f953086f090a022f2c0e1448300c15372db46.tar.xz | |
ALSA: usb-audio: Fix irq/process data synchronization
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>
Diffstat (limited to 'sound/usb/endpoint.c')
| -rw-r--r-- | sound/usb/endpoint.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 15d1d5c63c3c..2f0ea70a998c 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; } @@ -912,9 +917,7 @@ 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 @@ -924,7 +927,7 @@ 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; @@ -938,8 +941,6 @@ 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; @@ -1020,10 +1021,6 @@ 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); } } |