kernel - Fix MP race in sysv semaphore code
* Fix a serious MP race in the sysv semaphore code due to a lack of
protection of the semu* global structures.
* The race occurs during semaphore allocation and deallocation vs ANY
exiting process (even if it does not use semaphores), potentially
leading to a live-lock in the semu_list scan code.
The live-lock will prevent the cpu it occurs on from being able to
switch to another kernel or user thread. In the sample case it
stopped pagedaemon from running, creating a backlog in the I/O
subsystem which locked the computer up.
Reported-by: Peter Avalos