[alsa-devel] [PATCH 0/2] Fix thread safety issues

Jerome Forissier jerome at taodyne.com
Wed Jan 30 16:22:15 CET 2013

This is a set of two patches to fix thread safety issues I found when running
a video application over ALSA. The application uses LibVLC to play several
videos simultaneously. LibVLC calls snd_pcm_open() and snd_device_name_hint()
from multiple threads, without locking--which is allowed according to

Without these patches, I would get random error messages like:

ALSA lib confmisc.c:768:(parse_card) cannot find card '$CARD'
ALSA lib conf.c:4184:(_snd_config_evaluate) function snd_func_card_driver returned error: No such device
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4184:(_snd_config_evaluate) function snd_func_concat returned error: No such device
ALSA lib confmisc.c:1251:(snd_func_refer) error evaluating name
ALSA lib conf.c:4184:(_snd_config_evaluate) function snd_func_refer returned error: No such device
ALSA lib conf.c:4663:(snd_config_expand) Evaluate error: No such device

Jerome Forissier (2):
  Make snd_device_name_hint() thread-safe by locking a mutex
  snd_pcm_direct_parse_open_conf(): use thread-safe getgrnam_r()

 src/control/namehint.c | 31 +++++++++++++++++++++++++++++++
 src/pcm/pcm_direct.c   | 15 +++++++++++----
 2 files changed, 42 insertions(+), 4 deletions(-)


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