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DateSat, 11 Jan 1997 08:07:04 +0100 (MET)
FromMichel LESPINASSE <>
Subjectnfs deadlock problem in kernel 2.0.27 ?
Sorry, this is a repost.... I mailed this two days ago and apparently it
didn't made up to the list
This is about a process locked in the 2.0.27 "stable" kernel and
unkillable.

PS : the process is still running.... if you want me to collect more
debugging information....
----
I had a problem twice with the 2.0.27 kernel, I think this is a bug in the
nfs filesystem code.

When accessing remote filesystems, it sometimes happens that the reading
process gets locked. I think that it is locked inside the kernel, because
it is impossible to kill -9 it.

It happened to me twice when I used the update command in the debian
deselect package. I did tons of other accesses on this volume, but none of
them triggered this bug.... (I cannot explain this)
The system is still running, but this console is locked and I cannot
unmount this partition because of the open file. Here is what I can see in
another console :

8:31 [root:2] Studio:~# lsof /mnt/debian
COMMAND     PID     USER   FD   TYPE     DEVICE   SIZE/OFF      INODE NAME
zcat       2685     root    0r   REG     0,   2     158525  556423252
/mnt/debian (bouddha:/debian)

[the inode number seems much too big.... is this the reason for the bug
or the consequence of it ?]
8:31 [root:2] Studio:~# lsof -p 2685
COMMAND     PID     USER   FD   TYPE     DEVICE   SIZE/OFF      INODE NAME
zcat       2685     root  cwd    DIR     3,   1       1024      32774 /
(/dev/hda1)
zcat       2685     root  rtd    DIR     3,   1       1024          2 /
zcat       2685     root  mem    REG     3,   1      45280     149545 /
(/dev/hda1)
zcat       2685     root  mem    REG     3,   1      21448      20500 /
(/dev/hda1)
zcat       2685     root  mem    REG     3,   1     565296      20522 /
(/dev/hda1)
zcat       2685     root    0r   REG     0,   2     158525  556423252
/mnt/debian/rex-fixed/binary-i386/Packages.gz
zcat       2685     root    1w   REG     3,   1          0      33058 /
(/dev/hda1)
zcat       2685     root    2u   CHR     4,   1        0t0     125293
/dev/tty1
zcat       2685     root    3u  unix 0x0035d414        0t0
zcat       2685     root    4uw  REG     3,   1          0     167965 /
(/dev/hda1)

This nfs partition is mounted at boot-time with this entry in my fstab :
bouddha:/debian /mnt/debian nfs defaults,nodev,noexec,nosuid,rsize=8192,ro 
0 2

8:55 [root:2] Studio:~# kill -9 2685
8:55 [root:2] Studio:~#

the zcat process is still running, and in my locked console, I still see
the dselect message :
Uncompressing /mnt/debian/stable/binary-i386/Packages.gz ...


I feel this is strange, because all the accesses I made to this partition
with the usual shell tools never locked anything, but I got the lock
twice with dselect and always at the same place. Still I believe (correct
me if I'm wrong) that the problem cannot be in user space, because then
the kill -9 should work.

I am running the 2.0.27 kernel and bouddha is running Linux 2.0.22
If you want any more precisions, mail me. The process is still running.

Michel "Walken" LESPINASSE - Student at Ecole Centrale Paris (France)
           www               Email : walken@via.ecp.fr
          (o o)              VideoLan project : http://videolan.via.ecp.fr/
------oOO--(_)--OOo-------------------------------------------------------
Yow ! 1135 KB/s remote host TCP bandwidth over 10Mb/s ethernet. Beat that!

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