linux/sound
Takashi Iwai 67ec1072b0 ALSA: pcm: Fix rwsem deadlock for non-atomic PCM stream
A non-atomic PCM stream may take snd_pcm_link_rwsem rw semaphore twice
in the same code path, e.g. one in snd_pcm_action_nonatomic() and
another in snd_pcm_stream_lock().  Usually this is OK, but when a
write lock is issued between these two read locks, the problem
happens: the write lock is blocked due to the first reade lock, and
the second read lock is also blocked by the write lock.  This
eventually deadlocks.

The reason is the way rwsem manages waiters; it's queued like FIFO, so
even if the writer itself doesn't take the lock yet, it blocks all the
waiters (including reads) queued after it.

As a workaround, in this patch, we replace the standard down_write()
with an spinning loop.  This is far from optimal, but it's good
enough, as the spinning time is supposed to be relatively short for
normal PCM operations, and the code paths requiring the write lock
aren't called so often.

Reported-by: Vinod Koul <vinod.koul@intel.com>
Tested-by: Ramesh Babu <ramesh.babu@intel.com>
Cc: <stable@vger.kernel.org> # v3.18+
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2016-02-18 11:27:52 +01:00
..
aoa ALSA: aoa-soundbus: Switch to dev_pm_ops 2015-08-05 16:47:47 +02:00
arm ASoC: pxa: pxa-pcm-lib: switch over to snd-soc-dmaengine-pcm 2015-09-30 23:21:16 +01:00
atmel
core ALSA: pcm: Fix rwsem deadlock for non-atomic PCM stream 2016-02-18 11:27:52 +01:00
drivers ALSA: dummy: Implement timer backend switching more safely 2016-02-08 08:15:35 +01:00
firewire ALSA: firewire-digi00x: Drop bogus const type qualifier on dot_scrt() 2016-02-09 12:16:52 +01:00
hda ALSA: hda - Degrade i915 binding failure message 2016-01-20 15:00:26 +01:00
i2c ALSA: i2c: constify snd_i2c_ops structures 2015-11-30 11:40:08 +01:00
isa ALSA: Add missing dependency on CONFIG_SND_TIMER 2016-01-27 07:10:38 +01:00
mips
oss sound/oss: remove VIRT_TO_BUS dependency 2015-12-09 14:40:51 +01:00
parisc
pci ALSA: hda - Cancel probe work instead of flush at remove 2016-02-15 16:37:24 +01:00
pcmcia
ppc ALSA: ppc: Add missing inclusion of linux/module.h 2015-08-25 14:13:36 +02:00
sh
soc Merge remote-tracking branches 'asoc/fix/rt5659', 'asoc/fix/sigmadsp', 'asoc/fix/simple', 'asoc/fix/wm5110' and 'asoc/fix/wm8960' into asoc-linus 2016-02-10 19:23:09 +00:00
sparc ALSA: Add missing dependency on CONFIG_SND_TIMER 2016-01-27 07:10:38 +01:00
spi ALSA: at73c213: manage SSC clock 2016-01-20 09:59:27 +01:00
synth ALSA: emux: constify nrpn_conv_table structures 2016-01-06 10:19:49 +01:00
usb ALSA: usb-audio: avoid freeing umidi object twice 2016-02-13 09:30:58 +01:00
ac97_bus.c ASoC: Updates for v4.3 2015-08-31 16:25:22 +02:00
Kconfig
last.c
Makefile
sound_core.c sound: fix check for error condition of register_chrdev() 2015-11-07 11:14:30 +01:00
sound_firmware.c