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authorIoan-Adrian Ratiu <adi@adirat.com>2017-01-05 00:37:46 +0200
committerTakashi Iwai <tiwai@suse.de>2017-01-05 07:35:00 +0100
commit1d0f953086f090a022f2c0e1448300c15372db46 (patch)
tree96e89154873d3b08b73e18d717e33631cb050f67 /sound/usb/endpoint.h
parentc7efff9284dfde95a11aaa811c9d8ec8167f0f6e (diff)
downloadop-kernel-dev-1d0f953086f090a022f2c0e1448300c15372db46.zip
op-kernel-dev-1d0f953086f090a022f2c0e1448300c15372db46.tar.gz
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.h')
-rw-r--r--sound/usb/endpoint.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index 6428392..584f295 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);
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