Date: Sat, 8 Mar 2003 23:50:06 -0800 (PST) From: Nate Lawson <nate@root.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: cvs commit: src/sys/sys devicestat.h Message-ID: <Pine.BSF.4.21.0303082347200.90870-100000@root.org> In-Reply-To: <70769.1047194136@critter.freebsd.dk>
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On Sun, 9 Mar 2003, Poul-Henning Kamp wrote: > In message <Pine.BSF.4.21.0303081754050.90870-100000@root.org>, Nate Lawson wri > tes: > >> Revision Changes Path > >> 1.19 +14 -1 src/sys/sys/devicestat.h > > > >It would be nice to see some email on arch@ about this. There may have > >been others working on functionality in this area. > > I have floated patches recently but gotten very little response. Sorry, must have missed it. In general, I am interested in da(4) changes. > >Is there a reason for adding one element at the beginning and one at the > >end? Despite the fact this API is properly versioned, I believe accepted > >practice is to add items at the end unless other requirements supersede > >this one. > > Yes, these structures will be mmap'ed from kernel to userland and user > land will (likely) memcpy() them to private storage as snapshot'ing. > To be able to tell if you have an atomic snapshot, the two counters > must be identical. How about a mtx covering the structure and a read from the device returns the structure under lock? > To be able to do the mmap stunt, they have to be allocated from special > pages, so there is no option not to anymore. That's why there is only > one call. Ok. It's nice to see work in this area. -Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-src" in the body of the message
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