Re: 5.99.42/i386 crash (backtrace + core available)

[haad <haaaad%gmail.com@localhost>]

On Fri, Jan 7, 2011 at 12:35 AM, Dennis den Brok 
<denbrok%uni-bonn.de@localhost> wrote:
> (This discussion was temporarily held privately.)
>
> David Holland <dholland%netbsd.org@localhost> wrote:
>> Â> It very much seems to be the same crash; the backtrace is the same.
>> Â> After reproducing the crash on the console, I can now also say it's
>> Â> a "locking against myself" lock error indeed. The kernel is quite
>> Â> recent, so I don't think it's yamt's reverted changes.
>>
>> Probably advisable to check that explicitly. (Easy to do though; the
>> broken version is 1.126 of sys/kern/vfs_lookup.c.)
>>
>> Â> If it helps, I obtained a coredump produced with a DIAGNOSTIC+LOCKDEBUG
>> Â> kernel. I would need further instructions what to provide from
>> Â> that, though.
>>
>> The first thing to check is whether the vnode it's tripping over is
>> the same one it's trying to do lookup on. If it is, there's probably a
>> refcount bug somewhere in the call chain, and knowing it's there we/I
>> can probably find it. If it isn't... if it's some totally random
>> vnode, it's probably yet another race condition in vnode reclaim and
>> I'm not sure where to look. (I'm not really up on the vnode lifecycle
>> stuff yet.) However, if one of the vnodes is the nullfs projection of
>> the other, then it's probably fallout from Juergen's layer-locking
>> cleanup. Unfortunately I'm not sure how to check for that easily: the
>> layer_node inside the nullfs private vnode data contains a
>> layer_lowervp that points to the corresponding vnode from the
>> underlying fs, but extracting that with ddb may be somewhat painful.
>>
>> Another good thing to check is where the offending lock was originally
>> acquired; the code address appears in the LOCKDEBUG panic message so
>> it should just require translating that to a source location.
>>
>> Also, it's probably a good idea to take this back to the mailing list;
>> more eyes there.
>>
>> Â> I can now reliably reproduce the crash by grepping over the pkgsrc
>> Â> tree while pbulk is in the "scan" phase.
>
> I tried to get useful information from ddb, but ddb itself gets
> uvm faults as soon as I ask it for something interesting like a
> backtrace or information on locks, vnodes, etc., so unfortunately,
> I don't quite know where to go from here...


Maybe this can help you ?

http://wiki.netbsd.org/users/users/haad/ddb_howto/?updated#index2h2



-- 


Regards.

Adam