db_lock: new unified lock for songvec and dirvec

Makefile.am

@@ -248,6 +248,7 @@ src_mpd_SOURCES = \
 	src/directory_save.c \
 	src/database.c \
 	src/db_error.h \
+	src/db_lock.c src/db_lock.h \
 	src/db_save.c src/db_save.h \
 	src/db_print.c src/db_print.h \
 	src/db_plugin.h \

src/db_lock.c

+/*
+ * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "db_lock.h"
+
+GStaticMutex db_mutex = G_STATIC_MUTEX_INIT;

src/db_lock.h

+/*
+ * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/** \file
+ *
+ * Support for locking data structures from the database, for safe
+ * multi-threading.
+ */
+
+#ifndef MPD_DB_LOCK_H
+#define MPD_DB_LOCK_H
+
+#include "check.h"
+
+#include <glib.h>
+#include <assert.h>
+
+extern GStaticMutex db_mutex;
+
+/**
+ * Obtain the global database lock.  This is needed before
+ * dereferencing a #song or #directory.  It is not recursive.
+ */
+static inline void
+db_lock(void)
+{
+	g_static_mutex_lock(&db_mutex);
+}
+
+/**
+ * Release the global database lock.
+ */
+static inline void
+db_unlock(void)
+{
+	g_static_mutex_unlock(&db_mutex);
+}
+
+#endif

src/dirvec.c

@@ -20,6 +20,7 @@
 #include "config.h"
 #include "dirvec.h"
 #include "directory.h"
+#include "db_lock.h"
 
 #include <glib.h>
 
@@ -27,8 +28,6 @@
 #include <string.h>
 #include <stdlib.h>
 
-static GMutex *nr_lock = NULL;
-
 static size_t dv_size(const struct dirvec *dv)
 {
 	return dv->nr * sizeof(struct directory *);
@@ -42,24 +41,11 @@ static int dirvec_cmp(const void *d1, const void *d2)
 	return g_utf8_collate(a->path, b->path);
 }
 
-void dirvec_init(void)
-{
-	g_assert(nr_lock == NULL);
-	nr_lock = g_mutex_new();
-}
-
-void dirvec_deinit(void)
-{
-	g_assert(nr_lock != NULL);
-	g_mutex_free(nr_lock);
-	nr_lock = NULL;
-}
-
 void dirvec_sort(struct dirvec *dv)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	qsort(dv->base, dv->nr, sizeof(struct directory *), dirvec_cmp);
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 }
 
 struct directory *dirvec_find(const struct dirvec *dv, const char *path)
@@ -70,13 +56,13 @@ struct directory *dirvec_find(const struct dirvec *dv, const char *path)
 
 	base = g_path_get_basename(path);
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = dv->nr; --i >= 0; )
 		if (!strcmp(directory_get_name(dv->base[i]), base)) {
 			ret = dv->base[i];
 			break;
 		}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	g_free(base);
 	return ret;
@@ -86,13 +72,13 @@ int dirvec_delete(struct dirvec *dv, struct directory *del)
 {
 	size_t i;
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = 0; i < dv->nr; ++i) {
 		if (dv->base[i] != del)
 			continue;
 		/* we _don't_ call directory_free() here */
 		if (!--dv->nr) {
-			g_mutex_unlock(nr_lock);
+			db_unlock();
 			g_free(dv->base);
 			dv->base = NULL;
 			return i;
@@ -103,25 +89,25 @@ int dirvec_delete(struct dirvec *dv, struct directory *del)
 		}
 		break;
 	}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	return i;
 }
 
 void dirvec_add(struct dirvec *dv, struct directory *add)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	++dv->nr;
 	dv->base = g_realloc(dv->base, dv_size(dv));
 	dv->base[dv->nr - 1] = add;
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 }
 
 void dirvec_destroy(struct dirvec *dv)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	dv->nr = 0;
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 	if (dv->base) {
 		g_free(dv->base);
 		dv->base = NULL;
@@ -134,20 +120,20 @@ int dirvec_for_each(const struct dirvec *dv,
 	size_t i;
 	size_t prev_nr;
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = 0; i < dv->nr; ) {
 		struct directory *dir = dv->base[i];
 
 		assert(dir);
 		prev_nr = dv->nr;
-		g_mutex_unlock(nr_lock);
+		db_unlock();
 		if (fn(dir, arg) < 0)
 			return -1;
-		g_mutex_lock(nr_lock); /* dv->nr may change in fn() */
+		db_lock(); /* dv->nr may change in fn() */
 		if (prev_nr == dv->nr)
 			++i;
 	}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	return 0;
 }

src/dirvec.h

@@ -27,10 +27,6 @@ struct dirvec {
 	size_t nr;
 };
 
-void dirvec_init(void);
-
-void dirvec_deinit(void);
-
 void dirvec_sort(struct dirvec *dv);
 
 struct directory *dirvec_find(const struct dirvec *dv, const char *path);

src/main.c

@@ -54,8 +54,6 @@
 #include "dbUtils.h"
 #include "zeroconf.h"
 #include "event_pipe.h"
-#include "dirvec.h"
-#include "songvec.h"
 #include "tag_pool.h"
 #include "mpd_error.h"
 
@@ -346,8 +344,6 @@ int mpd_main(int argc, char *argv[])
 	io_thread_init();
 	winsock_init();
 	idle_init();
-	dirvec_init();
-	songvec_init();
 	tag_pool_init();
 	config_global_init();
 
@@ -534,8 +530,6 @@ int mpd_main(int argc, char *argv[])
 #endif
 	config_global_finish();
 	tag_pool_deinit();
-	songvec_deinit();
-	dirvec_deinit();
 	idle_deinit();
 	stats_global_finish();
 	io_thread_deinit();

src/songvec.c

@@ -21,6 +21,7 @@
 #include "songvec.h"
 #include "song.h"
 #include "tag.h"
+#include "db_lock.h"
 
 #include <glib.h>
 
@@ -28,8 +29,6 @@
 #include <string.h>
 #include <stdlib.h>
 
-static GMutex *nr_lock = NULL;
-
 static const char *
 tag_get_value_checked(const struct tag *tag, enum tag_type type)
 {
@@ -119,24 +118,11 @@ static size_t sv_size(const struct songvec *sv)
 	return sv->nr * sizeof(struct song *);
 }
 
-void songvec_init(void)
-{
-	g_assert(nr_lock == NULL);
-	nr_lock = g_mutex_new();
-}
-
-void songvec_deinit(void)
-{
-	g_assert(nr_lock != NULL);
-	g_mutex_free(nr_lock);
-	nr_lock = NULL;
-}
-
 void songvec_sort(struct songvec *sv)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	qsort(sv->base, sv->nr, sizeof(struct song *), songvec_cmp);
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 }
 
 struct song *
@@ -145,14 +131,14 @@ songvec_find(const struct songvec *sv, const char *uri)
 	int i;
 	struct song *ret = NULL;
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = sv->nr; --i >= 0; ) {
 		if (strcmp(sv->base[i]->uri, uri))
 			continue;
 		ret = sv->base[i];
 		break;
 	}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 	return ret;
 }
 
@@ -161,7 +147,7 @@ songvec_delete(struct songvec *sv, const struct song *del)
 {
 	size_t i;
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = 0; i < sv->nr; ++i) {
 		if (sv->base[i] != del)
 			continue;
@@ -174,10 +160,10 @@ songvec_delete(struct songvec *sv, const struct song *del)
 				(sv->nr - i) * sizeof(struct song *));
 			sv->base = g_realloc(sv->base, sv_size(sv));
 		}
-		g_mutex_unlock(nr_lock);
+		db_unlock();
 		return i;
 	}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	return -1; /* not found */
 }
@@ -185,18 +171,18 @@ songvec_delete(struct songvec *sv, const struct song *del)
 void
 songvec_add(struct songvec *sv, struct song *add)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	++sv->nr;
 	sv->base = g_realloc(sv->base, sv_size(sv));
 	sv->base[sv->nr - 1] = add;
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 }
 
 void songvec_destroy(struct songvec *sv)
 {
-	g_mutex_lock(nr_lock);
+	db_lock();
 	sv->nr = 0;
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	g_free(sv->base);
 	sv->base = NULL;
@@ -209,7 +195,7 @@ songvec_for_each(const struct songvec *sv,
 	size_t i;
 	size_t prev_nr;
 
-	g_mutex_lock(nr_lock);
+	db_lock();
 	for (i = 0; i < sv->nr; ) {
 		struct song *song = sv->base[i];
 
@@ -217,14 +203,14 @@ songvec_for_each(const struct songvec *sv,
 		assert(*song->uri);
 
 		prev_nr = sv->nr;
-		g_mutex_unlock(nr_lock); /* fn() may block */
+		db_unlock(); /* fn() may block */
 		if (fn(song, arg) < 0)
 			return -1;
-		g_mutex_lock(nr_lock); /* sv->nr may change in fn() */
+		db_lock(); /* sv->nr may change in fn() */
 		if (prev_nr == sv->nr)
 			++i;
 	}
-	g_mutex_unlock(nr_lock);
+	db_unlock();
 
 	return 0;
 }