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pcm: Better understandable locking code

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The newly added locking code seems to have confused quite a few
people, as "thread_safe=1" may be considered as if the thread-safety
lock has to be turned on.  (It meant that the plugin _is_ thread-safe,
i.e. it needs no extra locking.)

For avoiding such a misunderstanding, this commit renames the relevant
pcm fields and give more comments to explain what is for what.
The former single pcm->thread_safe flag is now split to two boolean
flags, pcm->need_lock and pcm->lock_enabled.  It consumes a few more
bytes, but this would be (hopefully) better understandable.

No functional change by this commit.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2016-09-01 14:05:00 +02:00
parent 3b08152f68
commit 0fc4b4d17b
3 changed files with 34 additions and 11 deletions
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16
src/pcm/pcm.c
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@ -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;