SVR4 vs BSD (was AIX (is it unix)?)

[Chris Torek]

>>... semaphored memory

In article <2508 at auspex.auspex.com> guy at auspex.auspex.com (Guy Harris) writes:
>"Semaphored memory"?

Oops, typo: I meant `semaphore memory'.  The mmap() call in 4.4BSD will
(assuming it gets implemented!) require a special flag (which might well
be a pseudo-flag, i.e., 0) in order to map for use as semaphores.  As
Kirk put it,

    I believe that shared memory is an interesting IPC mechanism only
    if semaphores can be mostly done without system calls, and hence
    must be provided for in the interface. HASSEMAPHORE provides this
    hook; some multiprocessors require that semaphores be in uncached
    memory or only in semaphore registers. This flag would allow the
    system to set up such uncached regions when it knew that semaphores
    were going to be used. For machines with hardware semaphore
    registers, the flag would cause the mmap with HASSEMAPHORE set to
    fail on anything other than a mapping of the special device
    associated with those registers.

Presumably the interface to semaphores used for shared memory will
be hidden in a library routine.

>OK, you were referring to the *interface* design ...

Quite.

>[which] is derived from the stuff described in the 4.2BSD paper, but not
>implemented in 4.xBSD (except perhaps trivially for some device drivers,
>just as was the case in SunOS prior to 4.0.)

(Not even in any drivers.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris