Re: [PATCH 2/3] KVM: Use kvm_free_assigned_irq() for free irq

[Sheng Yang <sheng@linux.intel.com>]

On Tuesday 30 December 2008 19:16:27 Avi Kivity wrote:
> Sheng Yang wrote:
> >> This will call cancel_work_sync(), which may wait upon kvm->lock, which
> >> I think we hold here -> deadlock.
> >>
> >> I think that the current code has even bigger problems (races), since a
> >> scheduled work can arrive after the interrupt has been freed and
> >> reallocated.
> >
> > For the race problem, how about put a cancel_work_sync() for all devices
> > at the beginning of kvm_destroy_vm? Something named
> > kvm_arch_cancel_work_sync...
>
> There is no race at destroy time since the work_struct has a reference
> on struct kvm.  So destruction is only triggered after the last interrupt.
>
> (but what if we get another interrupt immediately afterwards?!)

I don't like that reference, I think we can get it done more elegantly...

Yes, for MSI, we didn't disable interrupt, so got trouble.

So still, how about deal with this at the beginning of kvm_destory_vm? Discard 
currently reference count. In the function, disable all known interrupt(and 
result some nested disabled but we would free them later), then 
cancel_work_sync(). At this time, I think the state is legal(at least 
workable).

-- 
regards
Yang, Sheng