oops, I misread that as "if thread A locks the mutex, then..."
I haven't tried it in a single thread either, but lock followed immediately by destroy should also result in a crash in an unpatched nsd. The man page says,
pthread_mutex_destroy destroys a mutex object, freeing the
resources it might hold. The mutex must be unlocked on
entrance.
(with my patch, doing this will cause your thread to loop indefinitely. I don't really consider that a drawback, because in normal use if you forget to issue an unlock call you will also see an infinite block next time another thread tries to lock that mutex.)
