Date: Tue, 7 Apr 1998 17:07:08 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: michaelh@cet.co.jp (Michael Hancock) Cc: gurney_j@resnet.uoregon.edu, freebsd-current@FreeBSD.ORG Subject: Re: kernel support for memory semaphores/locks... Message-ID: <199804072207.RAA00583@dyson.iquest.net> In-Reply-To: <Pine.SV4.3.95.980408065757.6997A-100000@parkplace.cet.co.jp> from Michael Hancock at "Apr 8, 98 07:00:07 am"
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> On Tue, 7 Apr 1998, John-Mark Gurney wrote: > > > I have writen a memory block based dynamic allocation system (mmalloc).. > > I was planning on using a lock to prevent multiple processes from > > accessing the allocation strutures... but the only real way is using > > SYSV semaphores... > > and these are bad because it's silly to have all the overhead of a syscall > to do locking. > > > so, how do we go about locking on a shared memory areas? > > > > after discussing this with a friend, ther HAS to be a lock based on a > > shared memory location... the problem with storing the SYSV semaphore > > semid is that there isn't an atomic way of obtaining the new semid > > and putting it in a shared location after a machine reboot... > > /usr/src/share/doc/papers/newvm.ascii.gz describes an interface that was > never implemented, but worth reading. > I believe that POSIX has a reasonable scheme. John To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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