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ALSA: pcm: Use recursive mutex

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The recent thread-safety pthread implementation caused deadlocks in
some situations, e.g. when an external plugin calls snd_pcm_state() in
its callback.  One can avoid the deadlock by carefully using the
unlocked version, but it's often error-prone, and it might be still
problem with the old binaries.

In this patch, we initialize the pthread mutex as recursive for fixing
such a problem.

Suggested-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2017-04-21 20:36:40 +02:00
parent fbc18ec771
commit 1cb217ead9
1 changed files with 7 additions and 1 deletions
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8
src/pcm/pcm.c
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@ -2581,6 +2581,10 @@ int snd_pcm_new(snd_pcm_t **pcmp, snd_pcm_type_t type, const char *name,
snd_pcm_stream_t stream, int mode)
{
snd_pcm_t *pcm;
#ifdef THREAD_SAFE_API
pthread_mutexattr_t attr;
#endif
pcm = calloc(1, sizeof(*pcm));
if (!pcm)
return -ENOMEM;
@ -2595,7 +2599,9 @@ int snd_pcm_new(snd_pcm_t **pcmp, snd_pcm_type_t type, const char *name,
pcm->fast_op_arg = pcm;
INIT_LIST_HEAD(&pcm->async_handlers);
#ifdef THREAD_SAFE_API
pthread_mutex_init(&pcm->lock, NULL);
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&pcm->lock, &attr);
/* use locking as default;
* each plugin may suppress this in its open call
*/