[nfs] process locks in "bo_wwait" on 6.4

[Attilio Rao]

2009/6/29 pluknet <pluknet at gmail.com>:
> 2009/6/29 Attilio Rao <attilio at freebsd.org>:
>> 2009/6/29 pluknet <pluknet at gmail.com>:
>>> 2009/6/29 Attilio Rao <attilio at freebsd.org>:
>>>> 2009/6/29 pluknet <pluknet at gmail.com>:
>>>>> 2009/6/29 Attilio Rao <attilio at freebsd.org>:
>>>>>> 2009/6/29 pluknet <pluknet at gmail.com>:
>>>>>>> 2009/6/29 Attilio Rao <attilio at freebsd.org>:
>>>>>>>> 2009/6/29 pluknet <pluknet at gmail.com>:
>>>>>>>>> 2009/6/26 pluknet <pluknet at gmail.com>:
>>>>>>>>>> 2009/6/26 pluknet <pluknet at gmail.com>:
>>>>>>>>>>> Hello.
>>>>>>>>>>>
>>>>>>>>>>> While building a module on nfs mounted /usr/src
>>>>>>>>>>> I got an unkillable process waiting forever in bo_wwait.
>>>>>>>>>>
>>>>>>>>>> Small note: iface on NFS server has mtu changed from 1500 to 1450.
>>>>>>>>>> Can this be a source of the problem?
>>>>>>>>>
>>>>>>>>> This is 100% reproducible. Lock in the same place. Any hints?
>>>>>>>>
>>>>>>>> Can you also show the value of ps?
>>>>>>>> A precise map of what processes are doing would give an help.
>>>>>>>> Also would be useful to printout traces for other threads and not only
>>>>>>>> the stucked one.
>>>>>>>>
>>>>>>>
>>>>>>> >From another run:
>>>>>>
>>>>>> I'm unable to see who would be locking the buffer object in question.
>>>>>> Do you have INVARIANT_SUPPORT/INVARIANTS on?
>>>>>
>>>>> Yes, I do both.
>>>>>
>>>>>> What revision of /usr/src/sys/kern/vfs_bio.c are you running with?
>>>>>>
>>>>>
>>>>> As of 6.4-R: CVS rev 1.491.2.12.4.1 / SVN rev 183531.
>>>>
>>>> Please try this patch and report.
>>>>
>>>> Thanks,
>>>> Attilio
>>>>
>>>> --- src/sys/nfsclient/nfs_vnops.c       2008/02/13 20:44:18     1.281
>>>> +++ src/sys/nfsclient/nfs_vnops.c       2008/03/22 09:15:15     1.282
>>>> @@ -33,7 +33,7 @@
>>>>  */
>>>>
>>>>  #include <sys/cdefs.h>
>>>> -__FBSDID("$FreeBSD:
>>>> /usr/local/www/cvsroot/FreeBSD/src/sys/nfsclient/nfs_vnops.c,v 1.281
>>>> 2008/02/13 20:44:18 attilio Exp $");
>>>> +__FBSDID("$FreeBSD:
>>>> /usr/local/www/cvsroot/FreeBSD/src/sys/nfsclient/nfs_vnops.c,v 1.282
>>>> 2008/03/22 09:15:15 jeff Exp $");
>>>>
>>>
>>> Do you refer to the whole svn r177493, or is its nfs part will be enough?
>>> This only vfs_vnops.c diff seems not applicable without underneath
>>> kernel part changes.
>>>
>>> I'll try. Thanks.
>>
>> The NFS part should be enough, though I don't understand why it
>> doesn't trigger a panic on STABLE_6 as long as, at least in my
>> revision, there is an assert for the buffer object lock to be held in
>> bufobj_wwait(). What's your sys/kern/vfs_bio.c rev?
>>
>
> As of 6.4-R.
> $FreeBSD: src/sys/kern/vfs_bio.c,v 1.491.2.12.4.1 2008/10/02 02:57:24
> kensmith Exp $

That's it, the revision doesn't have the assert.
If it does fix the problem for you, I will let you test a more
comprehensive patch as there is also at least another fix I want to
bring in along with this one (and the relative asserts).

Thanks,
Attilio


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