If you enter it n times, you have to unlock it n times again to let other threads lock it. An exception is the function g_static_rec_mutex_unlock_full(): that allows you to unlock a GStaticRecMutex completely returning the depth, (i.e. the number of times this mutex was locked). The depth can later be used to restore the state of the GStaticRecMutex by calling g_static_rec_mutex_lock_full(). Even though GStaticRecMutex is not opaque, it should only be used with the following functions. All of the g_static_rec_mutex_* functions can be used even if g_thread_init() has not been called.