conf.c: use portable way to initialize recursive mutex

PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP is not in POSIX, as _NP
(non-portable) suggests.

exposing such a symbol in musl libc would lock in the ABI for all
times and makes it impossible to do future changes to the under-
lying struct without hideous symbol versioning hacks.

use the portable way instead: pthread_once was designed for such
cases.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Tested-by: John Spencer <maillist-alsa@barfooze.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/src/conf.c b/src/conf.c
index bfed1c4..5ccc8e1 100644 (file)
--- a/src/conf.c
+++ b/src/conf.c
@@ -427,8 +427,8 @@ beginning:</P>
 #ifndef DOC_HIDDEN
 
 #ifdef HAVE_LIBPTHREAD
-static pthread_mutex_t snd_config_update_mutex =
-                               PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+static pthread_mutex_t snd_config_update_mutex;
+static pthread_once_t snd_config_update_mutex_once = PTHREAD_ONCE_INIT;
 #endif
 
 struct _snd_config {
@@ -472,8 +472,19 @@ typedef struct {
 
 #ifdef HAVE_LIBPTHREAD
 
+static void snd_config_init_mutex(void)
+{
+       pthread_mutexattr_t attr;
+
+       pthread_mutexattr_init(&attr);
+       pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+       pthread_mutex_init(&snd_config_update_mutex, &attr);
+       pthread_mutexattr_destroy(&attr);
+}
+
 static inline void snd_config_lock(void)
 {
+       pthread_once(&snd_config_update_mutex_once, snd_config_init_mutex);
        pthread_mutex_lock(&snd_config_update_mutex);
 }