ed e774df25e5 Add lock annotations to <sys/cdefs.h>.
Clang has support for annotating mutexes and code that uses mutexes to
validate certain aspects of thread safety:

- Whether acquiring/releasing locks is done properly (e.g., whether you
  unlock a mutex before leaving a function).
- Whether a lock is held while reading/writing data from/to memory.

Analysis is performed at the function level. Functions can be annotated
to indicate they:

- (try to) pick up a lock,
- release a lock,
- can only be called when (not) holding a lock,
- assert that a lock is held.

Variables and structure members can be annotated to indicate that they
are guarded by a certain lock. In C++, these annotations can refer
to both global variables, but also other class/structure members. In C,
it is only possible to refer to global variables.

This change adds wrappers for the annotations used by Clang to
<sys/cdefs.h>. They currently have no effect, but this is on purpose.
This change will be merged back to FreeBSD 9 and 10, which means we can
safely experiment with these annotations on HEAD without making it
harder to port changes back.

Reviewed by:	announced on arch@ and toolchain@
MFC after:	3 weeks
2014-09-01 18:27:04 +00:00
..
2014-08-31 17:56:54 +00:00