@@ -2545,14 +2545,20 @@ int snd_pcm_new(snd_pcm_t **pcmp, snd_pcm_type_t type, const char *name,
INIT_LIST_HEAD(&pcm->async_handlers);
#ifdef THREAD_SAFE_API
pthread_mutex_init(&pcm->lock, NULL);
+ /* use locking as default;
+ * each plugin may suppress this in its open call
+ */
+ pcm->need_lock = 1;
{
- static int default_thread_safe = -1;
- if (default_thread_safe < 0) {
+ /* set lock_enabled field depending on $LIBASOUND_THREAD_SAFE */
+ static int do_lock_enable = -1; /* uninitialized */
+
+ /* evaluate env var only once at the first open for consistency */
+ if (do_lock_enable == -1) {
char *p = getenv("LIBASOUND_THREAD_SAFE");
- default_thread_safe = !p || *p != '0';
+ do_lock_enable = !p || *p != '0';
}
- if (!default_thread_safe)
- pcm->thread_safe = -1; /* force to disable */
+ pcm->lock_enabled = do_lock_enable;
}
#endif
*pcmp = pcm;
@@ -1514,7 +1514,7 @@ int snd_pcm_hw_open_fd(snd_pcm_t **pcmp, const char *name,
pcm->poll_events = info.stream == SND_PCM_STREAM_PLAYBACK ? POLLOUT : POLLIN;
pcm->tstamp_type = tstamp_type;
#ifdef THREAD_SAFE_API
- pcm->thread_safe = 1;
+ pcm->need_lock = 0; /* hw plugin is thread-safe */
#endif
ret = snd_pcm_hw_mmap_status(pcm);
@@ -244,7 +244,12 @@ struct _snd_pcm {
void *private_data;
struct list_head async_handlers;
#ifdef THREAD_SAFE_API
- int thread_safe;
+ int need_lock; /* true = this PCM (plugin) is thread-unsafe,
+ * thus it needs a lock.
+ */
+ int lock_enabled; /* thread-safety lock is enabled on the system;
+ * it's set depending on $LIBASOUND_THREAD_SAFE.
+ */
pthread_mutex_t lock;
#endif
};
@@ -1085,24 +1090,36 @@ static inline void sw_set_period_event(snd_pcm_sw_params_t *params, int val)
#define PCMINABORT(pcm) (((pcm)->mode & SND_PCM_ABORT) != 0)
#ifdef THREAD_SAFE_API
+/*
+ * __snd_pcm_lock() and __snd_pcm_unlock() are used to lock/unlock the plugin
+ * forcibly even if it's declared as thread-safe. It's needed only for some
+ * codes that are thread-unsafe per design (e.g. snd_pcm_nonblock()).
+ *
+ * OTOH, snd_pcm_lock() and snd_pcm_unlock() are used to lock/unlock the plugin
+ * in normal situations. They do lock/unlock only when the plugin is
+ * thread-unsafe.
+ *
+ * Both __snd_pcm_lock() and snd_pcm_lock() (and their unlocks) wouldn't do
+ * any action when the whole locking is disabled via $LIBASOUND_THREAD_SAFE=0.
+ */
static inline void __snd_pcm_lock(snd_pcm_t *pcm)
{
- if (pcm->thread_safe >= 0)
+ if (pcm->lock_enabled)
pthread_mutex_lock(&pcm->lock);
}
static inline void __snd_pcm_unlock(snd_pcm_t *pcm)
{
- if (pcm->thread_safe >= 0)
+ if (pcm->lock_enabled)
pthread_mutex_unlock(&pcm->lock);
}
static inline void snd_pcm_lock(snd_pcm_t *pcm)
{
- if (!pcm->thread_safe)
+ if (pcm->lock_enabled && pcm->need_lock)
pthread_mutex_lock(&pcm->lock);
}
static inline void snd_pcm_unlock(snd_pcm_t *pcm)
{
- if (!pcm->thread_safe)
+ if (pcm->lock_enabled && pcm->need_lock)
pthread_mutex_unlock(&pcm->lock);
}
#else /* THREAD_SAFE_API */