Re: --grow RAID6 gives: md: md_do_sync() got signal ... exiting + hang

[NeilBrown <neilb@suse.de>]

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On Tue, 7 May 2013 14:08:14 +0200 Ole Tange <tange@binf.ku.dk> wrote:

> On Tue, May 7, 2013 at 1:54 PM, NeilBrown <neilb@suse.de> wrote:
> > On Tue, 7 May 2013 13:36:56 +0200 Ole Tange <tange@binf.ku.dk> wrote:
> >
> >> I am expanding my 9 harddisk RAID6 to 10 harddisk RAID6:
> :
> >> It is, however, hanging the system.
> :
> >> # 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.
> 
> > What does
> >   grep . /sys/block/md1/md/*
> > show? Or does it hang?
> 
> Hangs (ctrl-c works).
> 
> > 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
> 
> > Did the "mdadm --grow" appear to complete, and return to the shell prompt?
> 
> Yes.
> 
> > What kernel version?  What mdadm version?
> 
> $ mdadm --version
> mdadm - v3.2.5 - 18th May 2012
> 
> $ uname -r
> 3.2.0-0.bpo.1-amd64
> 
> > 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

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