config file processing: rewrite the locking - use one recursive mutex

Avoid configuration file processing races when multiple threads call
the *open() functions together (for example using alsaloop with
multiple -T jobs can reproduce this issue).

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/src/conf.c b/src/conf.c
index 5d8c5c92fc2835c52d52929902683a6fb83d2872..8939d62ec702482270dc8b1e12f0bb0d2a15a58f 100644 (file)
--- a/src/conf.c
+++ b/src/conf.c
@@ -425,6 +425,11 @@ beginning:</P>
 
 #ifndef DOC_HIDDEN
 
+#ifdef HAVE_LIBPTHREAD
+static pthread_mutex_t snd_config_update_mutex =
+                               PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+#endif
+
 struct _snd_config {
        char *id;
        snd_config_type_t type;
@@ -464,6 +469,25 @@ typedef struct {
        int ch;
 } input_t;
 
+#ifdef HAVE_LIBPTHREAD
+
+static inline void snd_config_lock(void)
+{
+       pthread_mutex_lock(&snd_config_update_mutex);
+}
+
+static inline void snd_config_unlock(void)
+{
+       pthread_mutex_unlock(&snd_config_update_mutex);
+}
+
+#else
+
+static inline void snd_config_lock(void) { }
+static inline void snd_config_unlock(void) { }
+
+#endif
+
 static int safe_strtoll(const char *str, long long *val)
 {
        long long v;
@@ -3318,6 +3342,7 @@ static int snd_config_hooks(snd_config_t *config, snd_config_t *private_data)
 
        if ((err = snd_config_search(config, "@hooks", &n)) < 0)
                return 0;
+       snd_config_lock();
        snd_config_remove(n);
        do {
                hit = 0;
@@ -3334,7 +3359,7 @@ static int snd_config_hooks(snd_config_t *config, snd_config_t *private_data)
                        if (i == idx) {
                                err = snd_config_hooks_call(config, n, private_data);
                                if (err < 0)
-                                       return err;
+                                       goto _err;
                                idx++;
                                hit = 1;
                        }
@@ -3343,6 +3368,7 @@ static int snd_config_hooks(snd_config_t *config, snd_config_t *private_data)
        err = 0;
        _err:
        snd_config_delete(n);
+       snd_config_unlock();
        return err;
 }
 
@@ -3692,10 +3718,6 @@ int snd_config_update_r(snd_config_t **_top, snd_config_update_t **_update, cons
        return 1;
 }
 
-#ifdef HAVE_LIBPTHREAD
-static pthread_mutex_t snd_config_update_mutex = PTHREAD_MUTEX_INITIALIZER;
-#endif
-
 /** 
  * \brief Updates #snd_config by rereading the global configuration files (if needed).
  * \return 0 if #snd_config was up to date, 1 if #snd_config was
@@ -3716,13 +3738,9 @@ int snd_config_update(void)
 {
        int err;
 
-#ifdef HAVE_LIBPTHREAD
-       pthread_mutex_lock(&snd_config_update_mutex);
-#endif
+       snd_config_lock();
        err = snd_config_update_r(&snd_config, &snd_config_global_update, NULL);
-#ifdef HAVE_LIBPTHREAD
-       pthread_mutex_unlock(&snd_config_update_mutex);
-#endif
+       snd_config_unlock();
        return err;
 }
 
@@ -3755,18 +3773,14 @@ int snd_config_update_free(snd_config_update_t *update)
  */
 int snd_config_update_free_global(void)
 {
-#ifdef HAVE_LIBPTHREAD
-       pthread_mutex_lock(&snd_config_update_mutex);
-#endif
+       snd_config_lock();
        if (snd_config)
                snd_config_delete(snd_config);
        snd_config = NULL;
        if (snd_config_global_update)
                snd_config_update_free(snd_config_global_update);
        snd_config_global_update = NULL;
-#ifdef HAVE_LIBPTHREAD
-       pthread_mutex_unlock(&snd_config_update_mutex);
-#endif
+       snd_config_unlock();
        /* FIXME: better to place this in another place... */
        snd_dlobj_cache_cleanup();
 
@@ -4657,7 +4671,7 @@ int snd_config_expand(snd_config_t *config, snd_config_t *root, const char *args
                snd_config_delete(subs);
        return err;
 }
-       
+
 /**
  * \brief Searches for a definition in a configuration tree, using
  *        aliases and expanding hooks and arguments.
@@ -4707,10 +4721,15 @@ int snd_config_search_definition(snd_config_t *config,
         *  if key contains dot (.), the implicit base is ignored
         *  and the key starts from root given by the 'config' parameter
         */
+       snd_config_lock();
        err = snd_config_search_alias_hooks(config, strchr(key, '.') ? NULL : base, key, &conf);
-       if (err < 0)
+       if (err < 0) {
+               snd_config_unlock();
                return err;
-       return snd_config_expand(conf, config, args, NULL, result);
+       }
+       err = snd_config_expand(conf, config, args, NULL, result);
+       snd_config_unlock();
+       return err;
 }
 
 #ifndef DOC_HIDDEN