[Qemu-devel] Re: [PATCH] fix halt emulation with icount and CONFIG_IOTHREAD (v2)

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-02-16 11:27, Paolo Bonzini wrote:
> On 02/16/2011 11:04 AM, Jan Kiszka wrote:
>> On 2011-02-16 10:57, Paolo Bonzini wrote:
>>> On 02/16/2011 10:46 AM, Jan Kiszka wrote:
>>>> What should this be good for? The iothread already kicks the vcpu if it
>>>> wants to acquire the contended global mutex.
>>>
>>> Assuming the VCPU is in the timedwait that Marcelo changed, the global
>>> mutex is free and the iothread will not kick the VCPU.
>>
>> Then why should it kick it at all?
> 
> To make it notice something changed in all_cpu_threads_idle---but that's 
> wrong, it should have been kicked in cpu_interrupt.
> 
>> If we change the halt condition, we should not kick the vcpus but only
>> signal the condition variable. Actually, I've a patch queued that skips
>> pointless qemu_thread_signal in qemu_cpu_kick for TCG.
> 
> Yes, I was kicking just because that's the wrapper that is used to 
> signal the condition variable---just like I was kicking in my patches to 
> eliminate timedwait.
> 
>>> So, perhaps the correct fix is to kick the cpu in cpu_interrupt, and all
>>> I wrote about timeouts and timers is wrong.  My patch would band-aid it.
>>
>> That's my strong suspect. We really need to understand what goes wrong.
> 
> I agree on both counts.
> 

FWIW, I've rebased most of your patches on top of my outstanding ones
and pushed them to

git://git.kiszka.org/qemu-kvm.git queues/kvm-upstream

Jan

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