Date: Tue, 7 Apr 1998 17:07:34 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: phk@critter.freebsd.dk (Poul-Henning Kamp) Cc: gurney_j@resnet.uoregon.edu, freebsd-current@FreeBSD.ORG Subject: Re: kernel support for memory semaphores/locks... Message-ID: <199804072207.RAA00588@dyson.iquest.net> In-Reply-To: <2165.891967475@critter.freebsd.dk> from Poul-Henning Kamp at "Apr 7, 98 06:44:35 pm"
next in thread | previous in thread | raw e-mail | index | archive | help
> > >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... > > Make your own lock with the cmp8xchg instruction, just like the kernel > does. Check the "lock" instruction on the i386. Also check out the > "mplock.[schwhatever]" somewhere in the kernel. > > >using assembly to do atomic locking isn't an option as you would have > >to spin on the lock... > > No, you'd go to sleep for a jiffy and check again... I belive a yield() > syscall is in the pipeline or maybe already in. > Yield is in the kernel. John To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199804072207.RAA00588>