[Pkg-xen-devel] Bug#770456: Bug#770456: Bug#770456: Please start a qemu process in domain 0.

[Stefan Bader]

On 01.12.2014 12:35, Ian Campbell wrote:
> On Thu, 2014-11-27 at 17:41 +0100, Stefan Bader wrote:
>> On 27.11.2014 12:18, Ian Campbell wrote:
>>> On Thu, 2014-11-27 at 11:02 +0100, Stefan Bader wrote:
>>>> On 21.11.2014 13:50, Ian Campbell wrote:
>>>>> Package: xen-utils-common
>>>>> Version: 4.4.0-1
>>>>> Severity: important
>>>>> Tags: patch
>>>>>
>>>>> Under some circumstances the xl toolstack needs to create a loopback
>>>>> mount of a guest disk in dom0 (e.g. in order to run pygrub). Depending
>>>>> on the nature of the guest disk (e.g. qcow2 or raw file image based)
>>>>> this can require a qemu instance in dom0.
>>>>>
>>>>> The upstream xencommons starts such a qemu on boot. The following patch
>>>>> adds this to the Debian packages init script as well.
>>>>>
>>>>> Once I have a bug number for this I will add it to debian/changelog and
>>>>> push the result to feature/bugNNNN as usual.
>>>>>
>>>>> Thanks,
>>>>> Ian.
>>>>>
>>>>
>> <old path removed>
>>
>>>> Not sure this already was handled but the --name argument of qemu_stop_real
>>>> seems a copy-and-paste bug.
>>>
>>> Yes it is, whoops!
>>>
>>>>  Playing with it right now, --exec instead of --name
>>>> also works out better since qemu-system-i386 is just about too long.
>>>
>>> So it is, so this is probably a good idea.
>>>
>>> Will you send an updated patch once you've finished testing?
>>>
>>
>> So not sure whether the bug processor can handle attachments but Thunderbird
>> tends to mess things up otherwise. Also I yet have to figure out the location of
>> the repo to make proper patches (sorry about that).
> 
> http://anonscm.debian.org/cgit/pkg-xen/xen.git
> 
>> Anyway attaching the diff between the current init script and the updated one.
>> There is one thing which I did not include there. That is a work around some
>> kernel bug (which should be fixed in Debian by now). Just for here I want to
>> avoid stepping into the case where the new package is installed with the broken
>> kernel because in that situation the dpkg starts a qemu which cannot attach
>> properly and in the end both hang and qemu has to be killed hard(er). All a bit
>> ugly. So this is likely nothing you need but just in case:
>>
>> (see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=763831)
> 
> Urk. I wonder if this explains some of the bugs about the initscript
> hanging we had around earlier.

At least that was what happened to me first.

> 
> Anyway, your diff seems to only add some code to xenstored_start, I was
> expecting a change to qemu_start -- did you find that code was OK in the
> end? Or did you end up switching to --exec?

Errm, that part was the addition I inlined. The updated change was the full diff
between current init script and your changes with the updated qemu_stop_real.
And that might have gone missing in the bug tracker at least. It hopefully has
survived in the cc that went directly... hopefully...

-Stefan
> 
> Thanks,
> Ian.
> 
>> -Stefan
>>
>>  xenstored_start()
>>  {
>>         log_progress_msg "xenstored"
>> +       #
>> +       # Work-around kernel regression where short name links of
>> +       # /proc/$$/exe get replaced on rename unconditionally. This
>> +       # should be fixed in the kernel but hitting a bad kernel is
>> +       # fatal with starting qemu in dom0 (dpkg/qemu hangs).
>> +       #
>> +       if [ -f $XENSTORED_PIDFILE ]; then
>> +               XSPID="$(cat $XENSTORED_PIDFILE)"
>> +               XSBIN="$(ls -la /proc/$XSPID/exe 2>/dev/null)"
>> +               XSBIN="${XSBIN#*-> }"
>> +               XSBIN="${XSBIN% (deleted)}"
>> +               if [ "$XSBIN" != "" ]; then
>> +                       if [ "$(basename $XSBIN)" = "xenstored.dpkg-new" ]; then
>> +                               return 1
>> +                       fi
>> +               fi
>> +       fi
>>         start-stop-daemon --start --quiet --pidfile "$XENSTORED_PIDFILE" --exec
>> "$XENSTORED" --test > /dev/null \
>>
>>
>> _______________________________________________
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>> Pkg-xen-devel at lists.alioth.debian.org
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> 
> 


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