Re: Error in comment in sys/mutex.h

[David Holland <dholland-tech%netbsd.org@localhost>]

On Thu, Jan 12, 2017 at 01:31:17AM +0000, Taylor R Campbell wrote:
 >    Currently, there's a long comment in src/sys/sys/mutex.h which reads in 
 >    part:
 > 
 >    ...
 >      *
 >      *      MUTEX_OWNER(owner)
 >      *              Returns the owner of the adaptive mutex (LWP address).
 >      *
 >      *      MUTEX_OWNED(owner)
 >      *              Returns non-zero if an adaptive mutex is currently
 >      *              held by an LWP.
 >      *
 >    ...
 > 
 >    It seems to me that the arguments of these two macros should be (mtx) 
 >    rather than (owner).
 > 
 >    Am I misunderstanding something?  Or should I fix it?   :)
 > 
 > Actually, `owner' is correct.  Specifically, these pick apart the bits
 > of the struct kmutex::mtx_owner field.  Some of the bits make up a
 > pointer, either struct lwp * or struct cpu_info *, but in an aligned
 > pointer some bits are always zero, and those bits are used for other
 > purposes.  See, e.g., the definition of mutex_owned in kern_mutex.c.

Maybe the naming should be adjusted to be less confusing :-)

-- 
David A. Holland
dholland%netbsd.org@localhost