[Linux-cluster] files with unknown state - locking problem?

[Robert Peterson]

German Staltari wrote:
> Hi, we have a 6 node cluster with FC4, kernel 2.6.16 and the CVS 
> STABLE branch of the cluster software. Sometimes, some processes 
> (courier imap) hangs in D state. When I execute "ls -la" in the "tmp" 
> directory (the directory is always the same, the same mailbox) of the 
> mailbox that it's triyng to access the process, the answer is really 
> slow and this is the output:
>
> ?---------  ? ?        ?           ?            ? 
> 1151074448.M345358P6861_courierlock.qmail-be-04
> ?---------  ? ?        ?           ?            ? 
> 1151074497.M326691P7647_courierlock.qmail-be-04
> ?---------  ? ?        ?           ?            ? 
> 1151074534.M524707P2198_courierlock.qmail-be-05
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:07 
> 1151074538.M785749P13408_courierlock.qmail-be-03
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:09 
> 1151074588.M917441P3132_courierlock.qmail-be-05
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:09 
> 1151074593.M62901P3189_courierlock.qmail-be-05
> ?---------  ? ?        ?           ?            ? 
> 1151074649.M845223P5214_courierlock.qmail-be-02
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
> 1151074656.M448306P28724_courierlock.qmail-be-06
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
> 1151074657.M188653P5302_courierlock.qmail-be-02
> ?---------  ? ?        ?           ?            ? 
> 1151074679.M821433P4979_courierlock.qmail-be-05
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
> 1151074690.M360083P5741_courierlock.qmail-be-02
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:07 
> 1151074701.M709923P29422_courierlock.qmail-be-06
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
> 1151074716.M544858P6016_courierlock.qmail-be-02
> -rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
> 1151074731.M21587P6179_courierlock.qmail-be-02
> ?---------  ? ?        ?           ?            ? 
> 1151074804.M241436P7410_courierlock.qmail-be-02
> ?---------  ? ?        ?           ?            ? 
> 1151074831.M678238P17302_courierlock.qmail-be-03
> ?---------  ? ?        ?           ?            ? 
> 1151074917.M42708P8494_courierlock.qmail-be-05
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
> 1151074918.M541477P14716_courierlock.qmail-be-04
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
> 1151074946.M520653P15248_courierlock.qmail-be-04
> ?---------  ? ?        ?           ?            ? 
> 1151075037.M234721P11020_courierlock.qmail-be-02
> ?---------  ? ?        ?           ?            ? 
> 1151075065.M951224P8598_courierlock.qmail-be-01
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
> 1151075082.M788480P11712_courierlock.qmail-be-02
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
> 1151075186.M911867P18565_courierlock.qmail-be-04
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
> 1151075210.M366861P13891_courierlock.qmail-be-02
> -rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
> 1151075217.M850817P13366_courierlock.qmail-be-05
> ?---------  ? ?        ?           ?            ? 
> 1151075252.M599978P32483_imapuid_4.qmail-be-05
>
> It seems like a lock problem, but not sure. Is there any other tool 
> that I can use to debug this?
> Thanks
> German
>
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Hi German,

I suspect you are right: The question marks in ls -l leads me to believe 
there
might be a problem somewhere regarding the locking of the files.  My 
theory is this:
ls -l calls a kernel stat function to get file statistics.  The stat 
tries to acquire an internal
lock (glock), but can't, so it displays what you see instead of valid 
values.

Perhaps courier imap is locking files, then hanging, and the process is 
somehow
hanging around with the lock intact, or else killed abnormally where the 
lock is not released.
Do you have any suggestions how we can recreate this problem in our lab?

Regards,

Bob Peterson
Red Hat Cluster Suite