From b51abed8355e5556886623b2772fa6b7598d2282 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Thu, 29 Nov 2018 08:02:49 +0100 Subject: ALSA: pcm: Call snd_pcm_unlink() conditionally at closing 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 Cc: Signed-off-by: Takashi Iwai --- sound/core/pcm_native.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'sound/core/pcm_native.c') diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 66c90f486af9..6afcc393113a 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2369,7 +2369,8 @@ int snd_pcm_hw_constraints_complete(struct snd_pcm_substream *substream) static void pcm_release_private(struct snd_pcm_substream *substream) { - snd_pcm_unlink(substream); + if (snd_pcm_stream_linked(substream)) + snd_pcm_unlink(substream); } void snd_pcm_release_substream(struct snd_pcm_substream *substream) -- cgit