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

[Peter Lieven]

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?

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

br,
peter

> 
> Jan
>