Commit f4a56d7e61f6c54faf8230fde91280c56f871c5c
2020-03-30T14:26:15
Enable thread-safety features in libdbus There are multiple SDL APIs that internally sink into dbus calls, e.g. battery status, thread priority. If those calls happen in different threads simultaneously it can result in dbus crashes. To abide by dbus's multithreading guidelines we must call dbus_threads_init_default() to enable dbus's internal locking mechanisms: https://dbus.freedesktop.org/doc/api/html/group__DBusThreads.html#gac7b8a7001befc3eaa8c6b043151008dc Additionally, access to a DBusMessage must be synchronized between threads. SDL was already abiding that guideline as the DBusMessage structs aren't shared. The following email from the dbus mailing list hints that arbitrating access to the DBusConnection on the SDL may also be required: https://lists.freedesktop.org/archives/dbus/2017-September/017306.html
diff --git a/src/core/linux/SDL_dbus.c b/src/core/linux/SDL_dbus.c
index 8a279b4..02579aa 100644
--- a/src/core/linux/SDL_dbus.c
+++ b/src/core/linux/SDL_dbus.c
@@ -65,6 +65,7 @@ LoadDBUSSyms(void)
SDL_DBUS_SYM(message_iter_get_arg_type);
SDL_DBUS_SYM(message_iter_recurse);
SDL_DBUS_SYM(message_unref);
+ SDL_DBUS_SYM(threads_init_default);
SDL_DBUS_SYM(error_init);
SDL_DBUS_SYM(error_is_set);
SDL_DBUS_SYM(error_free);
@@ -124,6 +125,11 @@ SDL_DBus_Init(void)
return; /* oh well */
}
+ if (!dbus.threads_init_default()) {
+ is_dbus_available = SDL_FALSE;
+ return;
+ }
+
dbus.error_init(&err);
/* session bus is required */
diff --git a/src/core/linux/SDL_dbus.h b/src/core/linux/SDL_dbus.h
index 6967cc9..9f77512 100644
--- a/src/core/linux/SDL_dbus.h
+++ b/src/core/linux/SDL_dbus.h
@@ -62,6 +62,7 @@ typedef struct SDL_DBusContext {
int (*message_iter_get_arg_type)(DBusMessageIter *);
void (*message_iter_recurse)(DBusMessageIter *, DBusMessageIter *);
void (*message_unref)(DBusMessage *);
+ dbus_bool_t (*threads_init_default)(void);
void (*error_init)(DBusError *);
dbus_bool_t (*error_is_set)(const DBusError *);
void (*error_free)(DBusError *);