Date: Tue, 14 Dec 2004 21:48:48 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Kris Kennaway <kris@obsecurity.org> Cc: Nate Lawson <nate@root.org> Subject: Re: cvs commit: src/sys/i386/i386 vm_machdep.c Message-ID: <200412142148.48019.jhb@FreeBSD.org> In-Reply-To: <20041215001034.GA60875@xor.obsecurity.org> References: <200411300618.iAU6IkQX065609@repoman.freebsd.org> <41BF6F44.2090407@root.org> <20041215001034.GA60875@xor.obsecurity.org>
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On Tuesday 14 December 2004 07:10 pm, Kris Kennaway wrote: > On Tue, Dec 14, 2004 at 02:55:00PM -0800, Nate Lawson wrote: > > >Erm, well, that's not always easy since sometimes when you panic you > > > can't talk to the other CPUs for whatever reason. Putting back the > > > proxy reset doesn't hurt for now but does restore functionality in at > > > least some cases. I'd rather have that then certain hard panics not > > > get into ddb because we couldn't get onto the BSP to run ddb. > > > > Perhaps you could give me some pointers on what is counted on to be > > working when panic() is called? I can't come up with a situation where > > the proxy code couldn't be used upon entry to ddb. If there were any > > cases like this, the proxy code wouldn't work for cpu_reset() either. > > Also, in such a case, it's hard to see how ddb could be usable since it > > tries to stop other processors, which requires similar code to the proxy. > > > > Or in other words, if you have enough capability to call panic() or > > break to ddb, then you have enough resources to do an IPI and get onto > > the BSP. > > NB: DDB often isn't usable on SMP machines thesedays, and will hang > when a panic tries to enter it. Try debug.kdb.stop_cpus=0 (sysctl and tunable) to prevent KDB from trying to stop the other CPUs. Another possible fix that ups@ has talked about is changing IPI_STOP to use an NMI rather than a vector (you can send NMI IPIs via the local APIC) so that IPI_STOP is more reliable. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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