When and when not to use CTLFLAG_MPSAFE with the SYSCTL macros..?

[Garrett Cooper]

Hi,
	I’ve been trying to figure out (because sysctl(9) is lacking) when to use CTLFLAG_MPSAFE. Is it strictly when dealing with SYSCTL_PROC handlers that do proper locking of shared resources, or are there other nuances that need to be handled?
	I’m also asking because SYSCTL_UQUAD, for instance, explicitly uses CTLFLAG_MPSAFE in the handler, which is a bit confusing.
Thanks!
-NGie