https://github.com/torvalds/linux
Revision 1d0f953086f090a022f2c0e1448300c15372db46 authored by Ioan-Adrian Ratiu on 04 January 2017, 22:37:46 UTC, committed by Takashi Iwai on 05 January 2017, 06:35:00 UTC
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>
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Tip revision: 1d0f953086f090a022f2c0e1448300c15372db46 authored by Ioan-Adrian Ratiu on 04 January 2017, 22:37:46 UTC
ALSA: usb-audio: Fix irq/process data synchronization
ALSA: usb-audio: Fix irq/process data synchronization
Tip revision: 1d0f953
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COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 96.0 KB |
Kbuild | -rw-r--r-- | 2.8 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 381.7 KB |
Makefile | -rw-r--r-- | 57.6 KB |
README | -rw-r--r-- | 722 bytes |
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