Date: Wed, 5 Apr 2000 09:44:08 -0400 (EDT) From: Brian Dean <brdean@unx.sas.com> To: Greg Lehey <grog@lemis.com> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, Brad Knowles <blk@skynet.be>, Jeroen Ruigrok/Asmodai <asmodai@wxs.nl>, Matthew Dillon <dillon@apollo.backplane.com>, current@FreeBSD.ORG Subject: Re: Vinum breakage (was: 2nd call for reviews and tests: buf->bio patch) Message-ID: <200004051344.JAA15337@dean.pc.sas.com> In-Reply-To: <20000405150203.B66569@freebie.lemis.com> from Greg Lehey at "Apr 5, 2000 03:02:03 pm"
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Greg Lehey wrote: > Technical explanation: A buffer header gets corrupted between the > time the top half of the driver issues the request to the disk > driver, and when the I/O completes. Currently, the evidence is > pointing towards the disk driver, but the corruption is of such an > unusual nature that it's difficult to guess what's going on. This type of bug sounds like a perfect candidate for using the kernel's hardware debug support (on IA32), and would allow you to take a trace trap and drop to the kernel debugger when anyone modifies the buffer header, assuming you can cover the corrupted area with the 4 debug registers available, which can cover a range of 16 bytes, in 4 byte chunks. This is exactly the type of situation that inspired me to add the support in the first place. Hopefully, when I get a little bit of time, I can merge the code that I use so that we can do this in a straight forward way from within the kernel debugger. -Brian -- Brian Dean brdean@unx.sas.com SAS Institute Inc. bsd@FreeBSD.ORG To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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