Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper

Sasha Levin
2011-05-30T10:06:03Z

On Mon, 2011-05-30 at 11:56 +0200, Ingo Molnar wrote:
> * Sasha Levin <levinsasha928@gmail.com> wrote:
>
> > I'm just saying that we're limited to as many VCPU threads as we
> > can create. br_read_lock() won't do anything on a non-VCPU thread,
> > which makes it impossible to test it on non-VCPUs.
>
> btw., i wondered about that limit - don't we want to fix it?
>
> I mean, there's no fundamental reason why brlocks should do 'nothing'
> in worker threads. In fact it's a subtle breakage waiting AFAICS.
>
Can they do anything useful without locking? I think we should work on
integrating an RCU and changing brlocks to use that instead of focusing
too much on the current implementation.
This will also fix that limit you don't like :)

> We should have enumeration for all threads that kvm starts, and that
> we can use for a generic pause/resume facility. Can you see anything
> that prevents that model?
>
Theres a difference between how you would pause a VCPU thread as opposed
to a non-VCPU thread, other than that - no. We could use a thread
manager.

> Thanks,
>
> Ingo

--

Sasha.