On Mon, Jun 18, 2012 at 08:11:40PM +0000, Myklebust, Trond wrote:
> 
> The next time that you see the hang, can you try to run the command
> 'echo "t" >/proc/sysrq-trigger' as root?
> If you can compile with CONFIG_SUNRPC_DEBUG, then an 'echo 0
> >/proc/sys/rpc_debug' might also be helpful.
> 
 I'm attaching the bzip2'd output from the trigger [ 151k before
compressing ] - I guess that the lines from 1346 (the backup script)
onwards, and particularly from 1417 (rsync in state D) are the parts
of most interest.  The last line is because I killed the backup with
Ctrl-C.

 For the debug: I assume /proc/sys/sunrpc/rpc_debug is the thing ?
It didn't seem to do anything (udev-181) - but I only looked at the
log, forgot to look at dmesg.

 I've also got an nfs_debug file there.  Tried echoing 0 to that,
reran the backup script but it now ends normally and there is still
nothing in dmesg.

 Created a short text file in /boot, backup ran normally.  Added
another kernel image, used 'rpcdebug -s -m rpc all' and the same for
nfs, this time it hung.  I suspect it isn't the rsync itself which
hangs, but updating or touching or deleting a status file.  Might be
totally wrong there.  Also, 0 in the debug file seems to turn it off.

 I've grepped the separate NFS and RPC messages into nfs-only.bz2
and rpc-only.bz2.

 Back to bisection.

ĸen
-- 
das eine Mal als Tragödie, das andere Mal als Farce