[Qemu-devel] Re: [RFC] make cpu creation happen inside the right thread.

[Marcelo Tosatti]

On Tue, Nov 03, 2009 at 12:35:08PM -0200, Glauber Costa wrote:
> Right now, we issue cpu creation from the i/o thread, and then shoot a thread
> from inside that code. Over the last months, a lot of subtle bugs were 
> reported,
> usually arising from the very fragile order of that initialization.
> 
> I propose we rethink that a little. This is a patch that received basic 
> testing
> only, and I'd  like to hear on the overall direction. The idea is to issue 
> the new
> thread as early as possible. The first direct benefits I can identify are that
> we no longer have to rely at on_vcpu-like schemes for issuing vcpu ioctls, 
> since
> we are already on the right thread. Apic creation has far less spots for race
> conditions as well.
> 
> I am implementing this on qemu-kvm first, since we can show the benefits of it
> a bit better in there (since we already support smp)
> 
> Let me know what you guys think

Makes sense to me. You still need on_vcpu for issuing vcpu ioctls though
(after initialization).