Date: Mon, 29 Jul 2002 08:14:32 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Don Lewis <dl-freebsd@catspoiler.org> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern kern_sysctl.c Message-ID: <XFMail.20020729081432.jhb@FreeBSD.org> In-Reply-To: <200207290514.g6T5EPwr065150@gw.catspoiler.org>
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On 29-Jul-2002 Don Lewis wrote: > On 28 Jul, John Baldwin wrote: > >> Actually, we need to rework the generic sysctl alogrithm in general to do >> copyin first of any new data values, lock, make changes and copy output to >> temporary variables, unlock, then do copyout. I talked about this in the >> SMPng document I posted several months ago but I guess few people read it. > > That's pretty much the conclusion that I came to. > > One question is whether we want to support calls where the old and new > pointers point to the same address. In the current implementation this > will result in the in-kernel value being unchanged, since the copyin > would fetch the data output by the copyout. The in-kernel value will > get changed to something else of if the order of the copyin and copyout > is reversed. I haven't had a chance to scan the source tree to see if > there are any sysctl() calls that do this. I think that's a bug not a feature. :) -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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