Re: [Qemu-devel] KVM brokenness due to IO thread changes

[Jan Kiszka <jan.kiszka@web.de>]

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Marcelo Tosatti wrote:
> Jan,
> 
> On Tue, Apr 28, 2009 at 09:40:01AM +0200, Jan Kiszka wrote:
>> Hi,
>>
>> this is a heads-up, maybe someone has some time to look into this over
>> the day: I seems like the IO thread changes caused a few regressions to
>> the KVM mode.
>>
>> When I keep this feature disabled, I see strange hick-ups of the event
>> delivery mechanism, and the guest stops once in a while for a second or
>> so. Attaching strace makes the whole process terminate early (looks like
>> it triggers a race in the signal handling). And when I enable the IO
>> thread, I immediately get a deadlock on qemu_global_mutex.
> 
> Yes its borked. The iothread should signal the vcpu thread whenever it
> wants to grab the mutex lock, because unlike kvm-userspace it does not
> drop the global mutex when entering guest mode (VCPU_RUN ioctl).
> 
> Anthony will commit patches to fix that soon.

Looking forward. It's far more efficient to test my infrastructure
changes against the KVM mode.

> 
>> Moreover:
>>   CC    i386-softmmu/vl.o
>> /data/qemu/vl.c:4380: warning: ‘qemu_calculate_timeout’ defined but not used
>>
>> Jan
> 
> BTW, can you please review the changes made to the debugging logic in
> the main loop sometime? (there's a debug_requested global now).
> 

Looks OK and works fine.

Jan


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