Pkg xen devel - Jan 2019 - Bug#869123: task xenconsoled blocked in state D after reboot

Package: xen-utils-4.4
Version: 4.4.1-9+deb8u9
Severity: normal

Hi,

Since the latest security update of the xen 4.4 packages we notice that
after rebooting a dom0, there's a chance that the xenconsoled process
ends up hanging in D state.

The kernel logs show these messages repeatedly:

INFO: task xenconsoled:1135 blocked for more than 120 seconds.
      Not tainted 3.16.0-4-amd64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
xenconsoled     D ffff88017ce2c628     0  1135      1 0x00000000
 ffff88017ce2c1d0 0000000000000286 0000000000012f40 ffff8800776b3fd8
 0000000000012f40 ffff88017ce2c1d0 ffff88017ccc7848 ffff8800776b3f20
 ffff88017ccc784c ffff88017ce2c1d0 00000000ffffffff ffff88017ccc7850
Call Trace:
 [<ffffffff81517095>] ? schedule_preempt_disabled+0x25/0x70
 [<ffffffff81518b33>] ? __mutex_lock_slowpath+0xd3/0x1d0
 [<ffffffff81518c4b>] ? mutex_lock+0x1b/0x2a
 [<ffffffff811c753d>] ? __fdget_pos+0x3d/0x50
 [<ffffffff811aba4a>] ? SyS_write+0x1a/0xa0
 [<ffffffff8151a48d>] ? system_call_fast_compare_end+0x10/0x15

Also:

-# cat /proc/1135/stack
[<ffffffff811c753d>] __fdget_pos+0x3d/0x50
[<ffffffff811aba4a>] SyS_write+0x1a/0xa0
[<ffffffff8151a48d>] system_call_fast_compare_end+0x10/0x15
[<ffffffffffffffff>] 0xffffffffffffffff

I have seen this happening multiple times now, and have never seen it in
the past with Xen on Jessie. The servers used are HP Proliant dl360 gen8
and gen9 types.

I have an empty dom0 in this state currently, so I could do more
investigation right now. If there's quick feedback on this bug, I can
probably keep it blacklisted for usage until monday.

Another problem that might possibly be related is the fact that the
serial console of the dom0 stops giving any output right at '(XEN) Dom0
has maximum 4 VCPUs'. But, that problem is already present for years,
and if that happens, we usually (argh) reboot again until it stays
responding. I haven't ever seen a proper explanation or fix for this
issue in the past years. But it's also happening right now here. When
doing a reboot later, during shutdown, the serial console (here attached
to the HP ilo virtual serial console) will suddenly start printing all
text like everything has been buffered somewhere.

But, I'm not touching this thing right now or trying anything yet. Hope
we can come up with some useful debugging steps that might help finding
this xenconsoled problem.

-- 
Thanks,
Hans van Kranenburg

tags 869123 + moreinfo
thanks

Hi Hans,

This is about the bug report about xenconsoled ending up in state D that
you filed before in the Debian bug tracker, against the Xen packages.

Your bug report was targeted at a Xen package in a Debian distribution
older than the current stable (Stretch).

Can you please help us by confirming that any of the following scenarios
does apply to your situation?

* I had this problem a long time ago. It was never solved, but I found a
workaround, which is ...
* I had this problem a long time ago, and I solved it by not using Xen
any more, but by doing ...
* I still experience this problem, and I'm still using Xen
3.2/4.1/4.4/etc. I cannot upgrade to Debian Stretch or Buster because ...
* I had this problem, and since upgrading to Stretch / Buster / ? it
seems it was solved, and I forgot to report it again. Please close it,
thanks.
* Other: ...

Note that even if you found a solution, it's still very useful to report
it back to our bug tracker. There might be someone else running into the
same problem, who can be helped with your information.

Please note that unless there's a response within a month from now, we
will close the bug report. If you discover this message later, and this
case is important to you, then you can try unarchiving the bug and
replying to it, or reach out to the maintainers email list at
pkg-xen-devel at lists.alioth.debian.org (no subscription required) and
post a message.

Thanks,
Hans van Kranenburg

Processing commands for control at bugs.debian.org:
> tags 869123 + moreinfo
Bug #869123 [xen-utils-4.4] task xenconsoled blocked in state D after reboot
Added tag(s) moreinfo.
> thanks
Stopping processing here.

Please contact me if you need assistance.
-- 
869123: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=869123
Debian Bug Tracking System
Contact owner at bugs.debian.org with problems

Your message dated Mon, 18 Feb 2019 13:34:28 +0000
with message-id <9b3aeb6f-13f7-3b69-d2b7-d1b184a50ead at mendix.com>
and subject line Re: task xenconsoled blocked in state D after reboot
has caused the Debian Bug report #869123,
regarding task xenconsoled blocked in state D after reboot
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
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-- 
869123: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=869123
Debian Bug Tracking System
Contact owner at bugs.debian.org with problems
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