Date: Tue, 30 Jun 1998 21:58:14 -0400 (EDT) From: "David E. Brooks Jr" <dbj@iglou.com> To: Terry Lambert <tlambert@primenet.com> Cc: hackers@FreeBSD.ORG Subject: Re: mlock()/mclear (was Re: Unsupport calls) Message-ID: <Pine.BSF.3.96.980630215745.3283B-100000@localhost> In-Reply-To: <Pine.BSF.3.96.980630190503.929A-100000@localhost>
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On Tue, 30 Jun 1998, David E. Brooks Jr wrote: [ This is in regards to implementing mlock()/mclear() ] > I haven't gotten very far (I'm re-reading relevant portions of _The > Design and Implementation of 4.4 BSD Operating System_ and lots of > stuff in section 9 right now), but I do have one question right off > the bat. Both mmap(2) and the newvm paper make mention of the > MAP_HASSEMAPHORE flag; Why is (or was) this necessary? All that comes > to mind is multi-processor systems and keeping any copies of that > page of memory synchronized. Hmm, I think I can answer my own question: Mmap() needs to know since any reference counts (for those waiting to lock) to a semaphore structure have to be decremented properly when/if a page containing a semaphore is munmap()-ed from memory (either explicitly or through process termination). -- Dave (Who is now only beginning to realize why nobody has whipped this out before...) -- David E. Brooks Jr dbj@iglou.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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