From owner-freebsd-current@FreeBSD.ORG Fri Aug 24 12:30:18 2007 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2B05916A420 for ; Fri, 24 Aug 2007 12:30:18 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id 067F413C478 for ; Fri, 24 Aug 2007 12:30:18 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 89AE548EC5; Fri, 24 Aug 2007 08:30:17 -0400 (EDT) Date: Fri, 24 Aug 2007 13:30:17 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Andrew Turner In-Reply-To: <20070824181627.57bed401@hermies.int.fubar.geek.nz> Message-ID: <20070824132409.W3900@fledge.watson.org> References: <20070824181627.57bed401@hermies.int.fubar.geek.nz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-current@freebsd.org Subject: Re: FreeBSD on xen hvm X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 24 Aug 2007 12:30:18 -0000 On Fri, 24 Aug 2007, Andrew Turner wrote: > 1) PREEMPTION Preemption causes the kernel to panic with a page fault. The > dmesg is available from [1]. Any chance it's possible to get a core for this, or attach GDB somehow to the VM? It looks like timing in Xen may be exposing a race in some or another subsystem with timers, but figuring out which subsystem it is will be most easily done if we can inspect the callout information, which is most easily done with GDB since you can inspect the callout structure more easily. If not, then we can add some printfs to extract the information, I expect, or extend DDB. We need to find out what the function pointer in the callout structure is for. > 3) INVARIANTS Invariants causes a panic from a page fault. See [2] for the > dmesg and backtrace. This appears to be in the start up of Audit as it creates a kernel thread. Possibly it's creating the thread too early, or possibly something else is going on. Can you try creating a kernel without options AUDIT and see if it works better, or if it just panics when the next thread is created? It sounds like Xen may start the timer firing sooner than on plain hardware, or possibly at a faster rate initially, and that's causing things to happen in a different order, so I expect we'll either bump into a series of races of this sort based on different ordering of events, or discover the timer isn't properly being disabled or managed in Xen :-). Robert N M Watson Computer Laboratory University of Cambridge > > I can provide people with more information to track down the problem > and try patches. > > Andrew > > [1] http://fubar.geek.nz/files/freebsd/xen/xen_crash_preemption.txt > [2] http://fubar.geek.nz/files/freebsd/xen/xen_crash_invariants.txt > > -- > Andrew Turner > http://fubar.geek.nz/blog/ > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >