[Qemu-devel] Re: [PATCH] vnc: threaded server depends on io-thread

[Jan Kiszka]

On 2011-03-09 12:32, Peter Lieven wrote:
> 
> Am 09.03.2011 um 12:25 schrieb Jan Kiszka:
> 
>> On 2011-03-09 12:05, Stefan Hajnoczi wrote:
>>> On Wed, Mar 9, 2011 at 10:57 AM, Corentin Chary
>>> <address@hidden> wrote:
>>>>>> The threaded VNC servers messed up with QEMU fd handlers without
>>>>>> any kind of locking, and that can cause some nasty race conditions.
>>>>>>
>>>>>> The IO-Thread provides appropriate locking primitives to avoid that.
>>>>>> This patch makes CONFIG_VNC_THREAD depends on CONFIG_IO_THREAD,
>>>>>> and add lock and unlock calls around the two faulty calls.
>>>>>
>>>>> qemu-kvm currently doesn't compile with --enable-io-thread. is there an 
>>>>> easy fix
>>>>> for this?
>>>>
>>>> If IO Thread is not available, I'm afraid that --disable-vnc-thread is
>>>> the only fix.
>>>> Or, you can try to define some global mutex acting like iothread
>>>> locks, but that doesn't sounds like an easy fix.
>>>
>>> Jan or Marcelo can help here but qemu-kvm has an iothread equivalent
>>> built in by default.  It should be possible to use that.
>>
>> qemu_mutex_lock/unlock_iothread is properly provided in qemu-kvm even
>> without --enable-io-thread. So that tree could temporarily disable the
>> new configure check until we got rid of the special qemu-kvm bits.
>> Corentin's patch is against upstream, that adjustment need to be made
>> once the commit is merged into qemu-kvm.
> 
> do i understand you right, that i should be able to use vnc-thread together 
> with qemu-kvm
> just now if I add Corentin's patch without the io-thread dependency?

Yep.

> 
> if yes, i will do and try if I can force a crash again.
> 

TIA,
Jan

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