From owner-freebsd-current Wed Apr 5 6:46:26 2000 Delivered-To: freebsd-current@freebsd.org Received: from lamb.sas.com (lamb.sas.com [192.35.83.8]) by hub.freebsd.org (Postfix) with ESMTP id E86A037B9DB for ; Wed, 5 Apr 2000 06:46:08 -0700 (PDT) (envelope-from brdean@unx.sas.com) Received: from mozart (mozart.unx.sas.com [149.173.6.8]) by lamb.sas.com (8.9.3/8.9.1) with SMTP id JAA10623; Wed, 5 Apr 2000 09:44:39 -0400 (EDT) Received: from dean.pc.sas.com by mozart (5.65c/SAS/Domains/5-6-90) id AA08034; Wed, 5 Apr 2000 09:44:09 -0400 Received: (from brdean@localhost) by dean.pc.sas.com (8.9.3/8.9.1) id JAA15337; Wed, 5 Apr 2000 09:44:08 -0400 (EDT) (envelope-from brdean) From: Brian Dean Message-Id: <200004051344.JAA15337@dean.pc.sas.com> Subject: Re: Vinum breakage (was: 2nd call for reviews and tests: buf->bio patch) In-Reply-To: <20000405150203.B66569@freebie.lemis.com> from Greg Lehey at "Apr 5, 2000 03:02:03 pm" To: Greg Lehey Date: Wed, 5 Apr 2000 09:44:08 -0400 (EDT) Cc: Poul-Henning Kamp , Brad Knowles , Jeroen Ruigrok/Asmodai , Matthew Dillon , current@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL61 (25)] Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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