rwatson at FreeBSD.org
Tue Aug 1 13:38:51 UTC 2006
On Tue, 1 Aug 2006, Robert Watson wrote:
> On Tue, 25 Jul 2006, Graham Menhennitt wrote:
>>>> Fatal trap 12: page fault while in kernel mode
>>>>> current process = 479 (mountd)
>>> I have the same panic reproducibly. Shutting off nfs_server_enable (i.e.
>>> mountd) in rc.conf prevents it. This is with 6-STABLE cvsupped yesterday.
>>> I'll get some more info and follow up the PR.
>> I rebuilt my kernel (to enable debugging) and now it doesn't panic. So it
>> seems that an old kernel (from around the end of May) with a new mountd
>> (from Sunday) will crash. But a new kernel with a new mountd won't.
> FYI, I've managed to reproduce this on a 7-CURRENT kernel, so will try to
> take a look at this in detail in the next few days. It looks like a race
> during socket connect/accept for UNIX domain sockets, likely involving
> simultaneous close, which may be a sign of a bug in mountd (or the like)
> that triggers it. Of course, the kernel shouldn't panic under those
> circumstances. :-)
On further reflection, this is simply a bug in the UNIX domain socket code,
and has to do with a race between an attempt to connect to a socket and the
socket being closed, such as may happen during a reboot. I'll do some more
digging and see about a possible fix for this.
Robert N M Watson
University of Cambridge
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