ALSA: pcm: Call snd_pcm_unlink() conditionally at closing

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commit b51abed835 upstream.

Currently the PCM core calls snd_pcm_unlink() always unconditionally
at closing a stream.  However, since snd_pcm_unlink() invokes the
global rwsem down, the lock can be easily contended.  More badly, when
a thread runs in a high priority RT-FIFO, it may stall at spinning.

Basically the call of snd_pcm_unlink() is required only for the linked
streams that are already rare occasion.  For normal use cases, this
code path is fairly superfluous.

As an optimization (and also as a workaround for the RT problem
above in normal situations without linked streams), this patch adds a
check before calling snd_pcm_unlink() and calls it only when needed.

Reported-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

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Takashi Iwai 2018-11-29 08:02:49 +01:00 • committed by Ben Hutchings

parent e82e90a1cb

commit c29efc2557

1 changed files with 2 additions and 1 deletions

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sound/core/pcm_native.c

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