Re: [Qemu-devel] [PULL v2 for-2.7 02/15] qapi: change QmpInputVisitor to QSLIST

[Paolo Bonzini]

On 01/08/2016 11:24, Marc-André Lureau wrote:
> Hi
> 
> ----- Original Message -----
>>
>>
>> On 27/07/2016 23:37, Laszlo Ersek wrote:
>>> It seems to me that QEMU deadlocks when it tries to emit the
>>> SPICE_DISCONNECTED event.
>>>
>>> (Note that I can't find "handle SPICE_DISCONNECTED" in the libvirtd log
>>> even in the successful case (i.e., when QEMU is built at the parent of
>>> 3d344c2aabb7).)
>>>
>>> Apparently audio_atexit() is triggered when QEMU is returning from
>>> main() -- or calling exit() --, which somehow results in QEMU trying to
>>> send a SPICE_DISCONNECTED event through the monitor? I guess the monitor
>>> has been long dead by then.
>>>
>>> Hmmm, this gives me an idea... What happens if I remove the following
>>> fragment from my domain XML?
>>>
>>>     <sound model='ich6'>
>>>       <address type='pci' domain='0x0000' bus='0x02' slot='0x07'
>>>       function='0x0'/>
>>>     </sound>
>>>
>>> Yeah, the hang disappears, shutdown works just fine. It's a spice audio
>>> bug after all, apparently. Sorry for reporting it in this thread! :) I'm
>>> adding Gerd to the address list.
>>>
>>> To reiterate: this patch (commit 3d344c2aabb7) does *not* cause the
>>> symptom, it only exposes an independent bug that causes the symptom.
>>> And, I can work around that for now, by removing sound devices.
>>
>> I think the issue here is that the monitor is gone by the time
>> audio_atexit is called.  It is caused by commit
>> c1111a24a3358ecd2f17be7c8b117cfe8bc5e5f8.
>>
>> The fix is to move the audio_atexit call to main before
>> qemu_chr_cleanup, but I'm not sure how to deal with coreaudio_atexit.
> 
> alternatively, cleanup the monitor before cleaning up the chardev? I was just 
> looking at that, see wip patch attached.

This patch is a good idea because it avoids a dangling pointer (and
avoids touching the mess that is coreaudio_atexit).

Paolo