K 10 svn:author V 3 mjg K 8 svn:date V 27 2016-12-31T16:37:47.075348Z K 7 svn:log V 340 MFC r301157: Microoptimize locking primitives by avoiding unnecessary atomic ops. Inline version of primitives do an atomic op and if it fails they fallback to actual primitives, which immediately retry the atomic op. The obvious optimisation is to check if the lock is free and only then proceed to do an atomic op. END