general: recoded snd_dlobj_ functions

- changed logic to get/put blocks
- added mutex locking of the symbol list
- added reference counting (do not free used dl handles)

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

src/control/control.c

@@ -94,8 +94,7 @@ int snd_ctl_close(snd_ctl_t *ctl)
 	}
 	err = ctl->ops->close(ctl);
 	free(ctl->name);
-	if (ctl->dl_handle)
-		snd_dlclose(ctl->dl_handle);
+	snd_dlobj_cache_put(ctl->open_func);
 	free(ctl);
 	return err;
 }
@@ -768,7 +767,6 @@ static int snd_ctl_open_conf(snd_ctl_t **ctlp, const char *name,
 #ifndef PIC
 	extern void *snd_control_open_symbols(void);
 #endif
-	void *h = NULL;
 	if (snd_config_get_type(ctl_conf) != SND_CONFIG_TYPE_COMPOUND) {
 		if (name)
 			SNDERR("Invalid type for CTL %s definition", name);
@@ -854,40 +852,22 @@ static int snd_ctl_open_conf(snd_ctl_t **ctlp, const char *name,
 #ifndef PIC
 	snd_control_open_symbols();
 #endif
-	open_func = snd_dlobj_cache_lookup(open_name);
+	open_func = snd_dlobj_cache_get(lib, open_name,
+			SND_DLSYM_VERSION(SND_CONTROL_DLSYM_VERSION), 1);
 	if (open_func) {
-		err = 0;
-		goto _err;
-	}
-	h = snd_dlopen(lib, RTLD_NOW);
-	if (h)
-		open_func = snd_dlsym(h, open_name, SND_DLSYM_VERSION(SND_CONTROL_DLSYM_VERSION));
-	err = 0;
-	if (!h) {
-		SNDERR("Cannot open shared library %s", lib);
-		err = -ENOENT;
-	} else if (!open_func) {
-		SNDERR("symbol %s is not defined inside %s", open_name, lib);
-		snd_dlclose(h);
+		err = open_func(ctlp, name, ctl_root, ctl_conf, mode);
+		if (err >= 0) {
+			(*ctlp)->open_func = open_func;
+			err = 0;
+		} else {
+			snd_dlobj_cache_put(open_func);
+		}
+	} else {
 		err = -ENXIO;
 	}
        _err:
 	if (type_conf)
 		snd_config_delete(type_conf);
-	if (err >= 0) {
-		err = open_func(ctlp, name, ctl_root, ctl_conf, mode);
-		if (err >= 0) {
-			if (h /*&& (mode & SND_CTL_KEEP_ALIVE)*/) {
-				snd_dlobj_cache_add(open_name, h, open_func);
-				h = NULL;
-			}
-			(*ctlp)->dl_handle = h;
-			err = 0;
-		} else {
-			if (h)
-				snd_dlclose(h);
-		}
-	}
 	free(buf);
 	free(buf1);
 	return err;

src/control/control_local.h

@@ -56,7 +56,7 @@ typedef struct _snd_ctl_ops {
 
 
 struct _snd_ctl {
-	void *dl_handle;
+	void *open_func;
 	char *name;
 	snd_ctl_type_t type;
 	const snd_ctl_ops_t *ops;

src/dlmisc.c

@@ -29,6 +29,9 @@
 
 #include "list.h"
 #include "local.h"
+#ifdef HAVE_LIBPTHREAD
+#include <pthread.h>
+#endif
 
 #ifndef DOC_HIDDEN
 #ifndef PIC
@@ -169,69 +172,140 @@ void *snd_dlsym(void *handle, const char *name, const char *version)
 
 /*
  * dlobj cache
- *
- * FIXME: add reference counter and proper locking
  */
 
 #ifndef DOC_HIDDEN
 struct dlobj_cache {
+	const char *lib;
 	const char *name;
-	void *obj;
+	void *dlobj;
 	void *func;
+	unsigned int refcnt;
 	struct list_head list;
 };
 
-static LIST_HEAD(pcm_dlobj_list);
+#ifdef HAVE_LIBPTHREAD
+static pthread_mutex_t snd_dlobj_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-void *snd_dlobj_cache_lookup(const char *name)
+static inline void snd_dlobj_lock(void)
 {
-	struct list_head *p;
-	struct dlobj_cache *c;
-
-	list_for_each(p, &pcm_dlobj_list) {
-		c = list_entry(p, struct dlobj_cache, list);
-		if (strcmp(c->name, name) == 0)
-			return c->func;
-	}
-	return NULL;
+	pthread_mutex_lock(&snd_dlobj_mutex);
 }
 
-int snd_dlobj_cache_add(const char *name, void *dlobj, void *open_func)
+static inline void snd_dlobj_unlock(void)
+{
+	pthread_mutex_unlock(&snd_dlobj_mutex);
+}
+#else
+static inline void snd_dlobj_lock(void) {}
+static inline void snd_dlobj_unlock(void) {}
+#endif
+
+static LIST_HEAD(pcm_dlobj_list);
+
+void *snd_dlobj_cache_get(const char *lib, const char *name,
+			  const char *version, int verbose)
 {
 	struct list_head *p;
 	struct dlobj_cache *c;
+	void *func, *dlobj = NULL;
+	int dlobj_close = 0;
 
+	snd_dlobj_lock();
 	list_for_each(p, &pcm_dlobj_list) {
 		c = list_entry(p, struct dlobj_cache, list);
-		if (strcmp(c->name, name) == 0)
-			return 0; /* already exists */
+		if (c->lib && lib && strcmp(c->lib, lib) != 0)
+			continue;
+		if (!c->lib && lib)
+			continue;
+		if (!lib && c->lib)
+			continue;
+		dlobj = c->dlobj;
+		if (strcmp(c->name, name) == 0) {
+			c->refcnt++;
+			func = c->func;
+			snd_dlobj_unlock();
+			return func;
+		}
+	}
+	if (dlobj == NULL) {
+		dlobj = snd_dlopen(lib, RTLD_NOW);
+		if (dlobj == NULL) {
+			if (verbose)
+				SNDERR("Cannot open shared library %s",
+						lib ? lib : "[builtin]");
+			snd_dlobj_unlock();
+			return NULL;
+		}
+		dlobj_close = 1;
+	}
+	func = snd_dlsym(dlobj, name, version);
+	if (func == NULL) {
+		if (verbose)
+			SNDERR("symbol %s is not defined inside %s",
+					name, lib ? lib : "[builtin]");
+		goto __err;
 	}
 	c = malloc(sizeof(*c));
 	if (! c)
-		return -ENOMEM;
+		goto __err;
+	c->refcnt = 1;
+	c->lib = lib ? strdup(lib) : NULL;
 	c->name = strdup(name);
-	if (! c->name) {
+	if ((lib && ! c->lib) || ! c->name) {
+		free((void *)c->name);
+		free((void *)c->lib);
 		free(c);
-		return -ENOMEM;
+	      __err:
+		if (dlobj_close)
+			snd_dlclose(dlobj);
+		snd_dlobj_unlock();
+		return NULL;
 	}
-	c->obj = dlobj;
-	c->func = open_func;
+	c->dlobj = dlobj;
+	c->func = func;
 	list_add_tail(&c->list, &pcm_dlobj_list);
-	return 0;
+	snd_dlobj_unlock();
+	return func;
+}
+
+int snd_dlobj_cache_put(void *func)
+{
+	struct list_head *p;
+	struct dlobj_cache *c;
+	unsigned int refcnt;
+
+	snd_dlobj_lock();
+	list_for_each(p, &pcm_dlobj_list) {
+		c = list_entry(p, struct dlobj_cache, list);
+		if (c->func == func) {
+			refcnt = c->refcnt;
+			if (c->refcnt > 0)
+				c->refcnt--;
+			snd_dlobj_unlock();
+			return refcnt == 1 ? 0 : -EINVAL;
+		}
+	}
+	snd_dlobj_unlock();
+	return -ENOENT;
 }
 
 void snd_dlobj_cache_cleanup(void)
 {
-	struct list_head *p;
+	struct list_head *p, *npos;
 	struct dlobj_cache *c;
 
-	while (! list_empty(&pcm_dlobj_list)) {
-		p = pcm_dlobj_list.next;
+	snd_dlobj_lock();
+	list_for_each_safe(p, npos, &pcm_dlobj_list) {
 		c = list_entry(p, struct dlobj_cache, list);
-		list_del(p);
-		snd_dlclose(c->obj);
-		free((void *)c->name); /* shut up gcc warning */
-		free(c);
+		if (c->refcnt == 0) {
+			list_del(p);
+			snd_dlclose(c->dlobj);
+			free((void *)c->name); /* shut up gcc warning */
+			free((void *)c->lib); /* shut up gcc warning */
+			free(c);
+		}
 	}
+	snd_dlobj_unlock();
 }
 #endif

src/pcm/pcm.c

@@ -2068,7 +2068,6 @@ static int snd_pcm_open_conf(snd_pcm_t **pcmp, const char *name,
 #ifndef PIC
 	extern void *snd_pcm_open_symbols(void);
 #endif
-	void *h = NULL;
 	if (snd_config_get_type(pcm_conf) != SND_CONFIG_TYPE_COMPOUND) {
 		char *val;
 		id = NULL;
@@ -2157,39 +2156,18 @@ static int snd_pcm_open_conf(snd_pcm_t **pcmp, const char *name,
 #ifndef PIC
 	snd_pcm_open_symbols();	/* this call is for static linking only */
 #endif
-	open_func = snd_dlobj_cache_lookup(open_name);
+	open_func = snd_dlobj_cache_get(lib, open_name,
+			SND_DLSYM_VERSION(SND_PCM_DLSYM_VERSION), 1);
 	if (open_func) {
-		err = 0;
-		goto _err;
-	}
-	h = snd_dlopen(lib, RTLD_NOW);
-	if (h)
-		open_func = snd_dlsym(h, open_name, SND_DLSYM_VERSION(SND_PCM_DLSYM_VERSION));
-	err = 0;
-	if (!h) {
-		SNDERR("Cannot open shared library %s",
-		       lib ? lib : "[builtin]");
-		err = -ENOENT;
-	} else if (!open_func) {
-		SNDERR("symbol %s is not defined inside %s", open_name,
-		       lib ? lib : "[builtin]");
-		snd_dlclose(h);
-		err = -ENXIO;
-	}
-       _err:
-	if (err >= 0) {
 		err = open_func(pcmp, name, pcm_root, pcm_conf, stream, mode);
 		if (err >= 0) {
-			if (h /*&& (mode & SND_PCM_KEEP_ALIVE)*/) {
-				snd_dlobj_cache_add(open_name, h, open_func);
-				h = NULL;
-			}
-			(*pcmp)->dl_handle = h;
+			(*pcmp)->open_func = open_func;
 			err = 0;
 		} else {
-			if (h)
-				snd_dlclose(h);
+			snd_dlobj_cache_put(open_func);
 		}
+	} else {
+		err = -ENXIO;
 	}
 	if (err >= 0) {
 		err = snd_config_search(pcm_root, "defaults.pcm.compat", &tmp);
@@ -2209,6 +2187,7 @@ static int snd_pcm_open_conf(snd_pcm_t **pcmp, const char *name,
 			snd_config_get_integer(tmp, &(*pcmp)->minperiodtime);
 		err = 0;
 	}
+       _err:
 	if (type_conf)
 		snd_config_delete(type_conf);
 	free(buf);
@@ -2304,8 +2283,7 @@ int snd_pcm_free(snd_pcm_t *pcm)
 	free(pcm->name);
 	free(pcm->hw.link_dst);
 	free(pcm->appl.link_dst);
-	if (pcm->dl_handle)
-		snd_dlclose(pcm->dl_handle);
+	snd_dlobj_cache_put(pcm->open_func);
 	free(pcm);
 	return 0;
 }

src/pcm/pcm_local.h

@@ -174,7 +174,7 @@ typedef struct {
 } snd_pcm_fast_ops_t;
 
 struct _snd_pcm {
-	void *dl_handle;
+	void *open_func;
 	char *name;
 	snd_pcm_type_t type;
 	snd_pcm_stream_t stream;

src/pcm/pcm_rate.c

@@ -61,6 +61,7 @@ struct _snd_pcm_rate {
 	snd_pcm_channel_area_t *pareas;	/* areas for splitted period (rate pcm) */
 	snd_pcm_channel_area_t *sareas;	/* areas for splitted period (slave pcm) */
 	snd_pcm_rate_info_t info;
+	void *open_func;
 	void *obj;
 	snd_pcm_rate_ops_t ops;
 	unsigned int get_idx;
@@ -1204,6 +1205,8 @@ static int snd_pcm_rate_close(snd_pcm_t *pcm)
 
 	if (rate->ops.close)
 		rate->ops.close(rate->obj);
+	if (rate->open_func)
+		snd_dlobj_cache_put(rate->open_func);
 	return snd_pcm_generic_close(pcm);
 }
 
@@ -1272,33 +1275,23 @@ static const char *const default_rate_plugins[] = {
 	"speexrate", "linear", NULL
 };
 
-static int rate_open_func(snd_pcm_rate_t *rate, const char *type)
+static int rate_open_func(snd_pcm_rate_t *rate, const char *type, int verbose)
 {
-	char open_name[64];
+	char open_name[64], lib_name[128], *lib = NULL;
 	snd_pcm_rate_open_func_t open_func;
 	int err;
 
 	snprintf(open_name, sizeof(open_name), "_snd_pcm_rate_%s_open", type);
-	open_func = snd_dlobj_cache_lookup(open_name);
-	if (!open_func) {
-		void *h;
-		char lib_name[128], *lib = NULL;
-		if (!is_builtin_plugin(type)) {
-			snprintf(lib_name, sizeof(lib_name),
+	if (!is_builtin_plugin(type)) {
+		snprintf(lib_name, sizeof(lib_name),
 				 "%s/libasound_module_rate_%s.so", ALSA_PLUGIN_DIR, type);
-			lib = lib_name;
-		}
-		h = snd_dlopen(lib, RTLD_NOW);
-		if (!h)
-			return -ENOENT;
-		open_func = snd_dlsym(h, open_name, NULL);
-		if (!open_func) {
-			snd_dlclose(h);
-			return -ENOENT;
-		}
-		snd_dlobj_cache_add(open_name, h, open_func);
+		lib = lib_name;
 	}
+	open_func = snd_dlobj_cache_get(lib, open_name, NULL, verbose);
+	if (!open_func)
+		return -ENOENT;
 
+	rate->open_func = open_func;
 	rate->rate_min = SND_PCM_PLUGIN_RATE_MIN;
 	rate->rate_max = SND_PCM_PLUGIN_RATE_MAX;
 	rate->plugin_version = SND_PCM_RATE_PLUGIN_VERSION;
@@ -1315,8 +1308,13 @@ static int rate_open_func(snd_pcm_rate_t *rate, const char *type)
 
 	/* try to open with the old protocol version */
 	rate->plugin_version = SND_PCM_RATE_PLUGIN_VERSION_OLD;
-	return open_func(SND_PCM_RATE_PLUGIN_VERSION_OLD,
-			 &rate->obj, &rate->ops);
+	err = open_func(SND_PCM_RATE_PLUGIN_VERSION_OLD,
+			&rate->obj, &rate->ops);
+	if (err) {
+		snd_dlobj_cache_put(open_func);
+		rate->open_func = NULL;
+	}
+	return err;
 }
 #endif
 
@@ -1373,21 +1371,21 @@ int snd_pcm_rate_open(snd_pcm_t **pcmp, const char *name,
 	if (!converter) {
 		const char *const *types;
 		for (types = default_rate_plugins; *types; types++) {
-			err = rate_open_func(rate, *types);
+			err = rate_open_func(rate, *types, 0);
 			if (!err) {
 				type = *types;
 				break;
 			}
 		}
 	} else if (!snd_config_get_string(converter, &type))
-		err = rate_open_func(rate, type);
+		err = rate_open_func(rate, type, 1);
 	else if (snd_config_get_type(converter) == SND_CONFIG_TYPE_COMPOUND) {
 		snd_config_iterator_t i, next;
 		snd_config_for_each(i, next, converter) {
 			snd_config_t *n = snd_config_iterator_entry(i);
 			if (snd_config_get_string(n, &type) < 0)
 				break;
-			err = rate_open_func(rate, type);
+			err = rate_open_func(rate, type, 0);
 			if (!err)
 				break;
 		}