Date: 23 Aug 1999 17:23:03 +0300 From: Ville-Pertti Keinonen <will@iki.fi> To: grog@lemis.com (Greg Lehey) Cc: hackers@freebsd.org Subject: Re: Mandatory locking? Message-ID: <86zoziwp88.fsf@not.demophon.com> In-Reply-To: grog@lemis.com's message of "23 Aug 1999 11:16:18 %2B0300" References: <19990823162813.I83273@freebie.lemis.com> <19990823174345.J83273@freebie.lemis.com>
next in thread | previous in thread | raw e-mail | index | archive | help
grog@lemis.com (Greg Lehey) writes: > Again, if we have two concurrent transactions, we stand to gain money: > the updated balance is likely not to know about the other transaction, > and will thus "forget" one of the deductions. > Now I suppose you're going to come and say that this is bad > programming, and advisory locking would do the job if the software is > written right. Correct. You could also use the same argument to say > that memory protection isn't necessary, because a correctly written > program doesn't overwrite other processes address space. It's the The difference is that if a program has privileges to screw up whatever you are protecting, it can do so even if you do have mandatory locking, simply by functioning incorrectly when it does gain access to the data. And even without otherwise incorrect behavior, if you have a program that doesn't use any locking and another one that uses mandatory locking to prevent races with the non-locking program, the mere existence of the locking program does not prevent multiple non-locking programs from generating similar conditions. (I'm not opposed to mandatory locking in principle, but I don't find your reasoning very convincing.) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?86zoziwp88.fsf>