This patch removes the stupid "Read locks within the self-held write
lock succeed" behaviour. This is breaking in mm_take_all_locks() since
it is quite common to ensure that a lock is taken with
BUG_ON(down_read_trylock(&mm->mmap_sem)).
Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>