io_thread: new thread for non-blocking background I/O

Try to eliminate the remaining blocking I/O.

Makefile.am

@@ -298,6 +298,7 @@ src_mpd_SOURCES = \
 	src/listen.c \
 	src/log.c \
 	src/ls.c \
+	src/io_thread.c src/io_thread.h \
 	src/main.c \
 	src/main_win32.c \
 	src/event_pipe.c \

src/io_thread.c

@@ -0,0 +1,85 @@
+/*
+ * 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 "io_thread.h"
+
+#include <assert.h>
+
+static GMainContext *io_context;
+static GMainLoop *io_loop;
+static GThread *io_thread;
+
+static gpointer
+io_thread_func(G_GNUC_UNUSED gpointer arg)
+{
+	assert(io_context != NULL);
+	assert(io_loop != NULL);
+
+	g_main_loop_run(io_loop);
+	return NULL;
+}
+
+void
+io_thread_init(void)
+{
+	assert(io_context == NULL);
+	assert(io_loop == NULL);
+	assert(io_thread == NULL);
+
+	io_context = g_main_context_new();
+	io_loop = g_main_loop_new(io_context, false);
+}
+
+bool
+io_thread_start(GError **error_r)
+{
+	assert(io_context != NULL);
+	assert(io_loop != NULL);
+	assert(io_thread == NULL);
+
+	io_thread = g_thread_create(io_thread_func, NULL, true, error_r);
+	if (io_thread == NULL)
+		return false;
+
+	return true;
+}
+
+void
+io_thread_deinit(void)
+{
+	if (io_thread != NULL) {
+		assert(io_loop != NULL);
+
+		g_main_loop_quit(io_loop);
+		g_thread_join(io_thread);
+	}
+
+	if (io_loop != NULL)
+		g_main_loop_unref(io_loop);
+
+	if (io_context != NULL)
+		g_main_context_unref(io_context);
+}
+
+GMainContext *
+io_thread_context(void)
+{
+	return io_context;
+}
+

src/io_thread.h

@@ -0,0 +1,39 @@
+/*
+ * 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.
+ */
+
+#ifndef MPD_IO_THREAD_H
+#define MPD_IO_THREAD_H
+
+#include <glib.h>
+#include <stdbool.h>
+
+void
+io_thread_init(void);
+
+bool
+io_thread_start(GError **error_r);
+
+void
+io_thread_deinit(void);
+
+G_GNUC_PURE
+GMainContext *
+io_thread_context(void);
+
+#endif

src/main.c

@@ -20,6 +20,7 @@
 #include "config.h"
 #include "main.h"
 #include "daemon.h"
+#include "io_thread.h"
 #include "client.h"
 #include "client_idle.h"
 #include "idle.h"
@@ -312,6 +313,7 @@ int mpd_main(int argc, char *argv[])
 	/* enable GLib's thread safety code */
 	g_thread_init(NULL);
 
+	io_thread_init();
 	winsock_init();
 	idle_init();
 	dirvec_init();
@@ -386,6 +388,12 @@ int mpd_main(int argc, char *argv[])
 
 	initSigHandlers();
 
+	if (!io_thread_start(&error)) {
+		g_warning("%s", error->message);
+		g_error_free(error);
+		return EXIT_FAILURE;
+	}
+
 	initZeroconf();
 
 	player_create(global_player_control);
@@ -474,6 +482,7 @@ int mpd_main(int argc, char *argv[])
 	dirvec_deinit();
 	idle_deinit();
 	stats_global_finish();
+	io_thread_deinit();
 	daemonize_finish();
 #ifdef WIN32
 	WSACleanup();