On Tue, 7 May 2013 14:08:14 +0200 Ole Tange [off-list ref] wrote:

On Tue, May 7, 2013 at 1:54 PM, NeilBrown [off-list ref] wrote:

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On Tue, 7 May 2013 13:36:56 +0200 Ole Tange [off-list ref] wrote:

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I am expanding my 9 harddisk RAID6 to 10 harddisk RAID6:

:

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It is, however, hanging the system.

:

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# Do the reshape
mdadm -v --grow /dev/md1 --raid-devices=10
--backup-file=/root/back-md1
mdadm: Need to backup 7168K of critical section..

This completed - did not hang.

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What does
  grep . /sys/block/md1/md/*
show? Or does it hang?

Hangs (ctrl-c works).

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What about "mdadm --examine /dev/sd*"

https://gist.github.com/anonymous/5532063

The disk box contains more drives than just the array in question. The
interesting array is: 242d6530:e2562ecb:1dcd2a97:15a1a868

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Did the "mdadm --grow" appear to complete, and return to the shell prompt?

Yes.

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What kernel version?  What mdadm version?

$ mdadm --version
mdadm - v3.2.5 - 18th May 2012

$ uname -r
3.2.0-0.bpo.1-amd64

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A hanging /proc/mdstat is definitely not a good sign.  The "got signal ...
exiting" isn't good either.  I would expect more messages with that.
You didn't just "grep md" in dmesg did you?  That is a complete dmesg output
for the entire time period that could possibly be relevant?

dmesg of controller upgrade (after which everything worked fine)
followed by --grow at 4328065.432267

https://gist.github.com/anonymous/5532093

/Ole

Thanks for the extra info.  I can't find any smoking gun unfortunately.

What does "ps axgu" show.  I'm particularly looking for processes in 'D'
state.
If there  are any, particularly if they are md related, try
  cat /proc/$PID/stack
for appropriate values of $PID

Maybe also try
   echo t > /proc/sysrq_trigger

and see what gets into 'dmesg' - hopefully your dmesg buffer is big enough to
hold the important stack traces.
If you get anything from either of those, please post.

NeilBrown