Main part here is making parallel lookups safe for RT - making sure preemption is disabled in start_dir_add()/ end_dir_add() sections (on non-RT it's automatic, on RT it needs to to be done explicitly) and moving wakeups from __d_lookup_done() inside of such to the end of those sections. Wakeups can be safely delayed for as long as ->d_lock on in-lookup dentry is held; proving that has caught a bug in d_add_ci() that allows memory corruption when sufficiently bogus ntfs (or case-insensitive xfs) image is mounted. Easily fixed, fortunately. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>