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Date: Mon, 9 Jul 2007 15:44:15 -0700 From: Randy Dunlap <randy.dunlap@...cle.com> To: "Jesper Juhl" <jesper.juhl@...il.com> Cc: "Charles Shannon Hendrix" <shannon@...omaker.com>, linux-kernel@...r.kernel.org Subject: Re: BUG: kernel crash report, odd... On Tue, 10 Jul 2007 00:29:54 +0200 Jesper Juhl wrote: > Forgot a few things, see below... > > On 10/07/07, Jesper Juhl <jesper.juhl@...il.com> wrote: > > On 10/07/07, Charles Shannon Hendrix <shannon@...omaker.com> wrote: > > > > > > A system I was using a few minutes ago dumped this to the syslog: > > > > > > Jul 9 17:50:38 daydream kernel: [76022.613000] BUG: unable to handle > > > kernel NUL > > > L pointer dereference at virtual address 00000010 > > > Jul 9 17:50:38 daydream kernel: [76022.613000] printing eip: > > > Jul 9 17:50:38 daydream kernel: [76022.613000] c01ace66 > > > Jul 9 17:50:38 daydream kernel: [76022.613000] *pde = 00000000 > > > Jul 9 17:50:38 daydream kernel: [76022.613000] Oops: 0000 [#1] > > > > > > > > > There was no other information either before or after. > > > > > > What I saw was my KDE desktop stopped responding to events. > > > > > > Machine didn't respond to power switch. > > > > > > Unfortunately, that's all I know. > > > > > > In the past when I had bugs like this, I got a fairly extensive kernel > > > error message, but this time the above is the only thing I saw. > > > > > It does look a little short... probably the rest just didn't make it to disk... > > > > > I have not had kernel bugs like this until I started running 2.6.20 on a > > > new Kubuntu install. > > > > > > Same hardware, but Slackware and my own custom 2.6.19 kernel never > > > crashed. > > > > > Different kernel source version, different configuration, probably > > different compiler, Slackware doesn't patch the vanilla kernel - I > > believe (k)ubuntu does. All in all that equals a significantly > > different kernel binary you have been running in those two cases. > > > A different userspace could also be the cause. In theory, userspace > should never be able to crash the kernel, but in real life bugs happen > and sometimes userspace manages to cause a kernel crash. So, a > different userspace environment in your new distribution could in > theory expose a bug that didn't surface with your previous > distribution. > > > > Is there anything I can do, in case this happens again, to try and > > > capture more information? > > > > > 0. Make sure the kernels loglevel is set so that you get all messages. i.e., boot with "ignore_loglevel" > 0.5. Perhaps increase the size of the kernels log buffer (the > LOG_BUF_SHIFT config option) or boot with "log_buf_len=n[KMG]" (power of 2 required) > > 1. Make sure syslog is setup to capture all kernel messages, both > > errors, warnings, notices, debug messages etc. > > > > 2. If you can, check output of 'dmesg' instead of just what made it to syslog. > > > > 3. If you have a second PC, setup serial console or netconsole to > > capture kernel messages on that second box. This can sometimes capture > > messages that don't make it to disk. > > > > 4. Build a custom kernel with some (or all) of the debug options under > > the Kernel Hacking menu enabled. > > > > 5. Even when the system hangs you may in some cases be able to get > > some info (or just sync the disks and do a reboot) via magic sysrq. --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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