Re: [kvm-devel] [PATCH] qemu-kvm: Consolidate kvm_eat_signals

[Avi K. <av...@qu...>]

Anthony Liguori wrote:
>>
>> Yes.  The loop was a (perhaps premature) optimization that is now 
>> totally unnecessary, unless I'm missing something quite large.
>>   
>
> It used to be that kvm_eat_signal() selected after consuming as many 
> signals as possible while only sleeping once.  That's why there's a 
> combination of sleeping and polling.
>

Yes.

> Now the VCPU threads never select so the whole loop can be simplified 
> to a single sigtimedwait() that always blocks.
>
> In reality, I don't think sigtimedwait() is really needed/useful for 
> VCPUs anymore.  We only use it to catch SIG_IPI and we only use 
> SIG_IPI to break out of sleeping.  I don't see any reason why we 
> couldn't switch over to using a file descriptor for notification (or a 
> pthread condition).

How would you stop a vcpu running in guest mode?

> In the very least, we could just select() on nothing and allow SIG_IPI 
> to break us out of the select.

sigtimedwait() (or just sigwait, now) doesn't require the signal to be 
delivered, so it's faster.

If there's nothing to select, why call select()?

-- 
error compiling committee.c: too many arguments to function