Re: [PATCH] kvm: get rid of srcu idx

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Oct 26, 2010 at 10:06:41AM +0200, Avi Kivity wrote:
>  On 10/26/2010 10:01 AM, Gleb Natapov wrote:
> >On Tue, Oct 26, 2010 at 09:57:08AM +0200, Avi Kivity wrote:
> >>   On 10/26/2010 08:58 AM, Gleb Natapov wrote:
> >>  >>
> >>  >>   Well, you just changed where srcu index is saved. I don't see how it
> >>  >>   could make a difference in practice.
> >>  >>
> >>  >If there is nested call to srcu read lock if srcu_idx is stored in vcpu
> >>  >nested call will override previous srcu_idx value and srcu unlock will
> >>  >not be called on it, but it will be called twice on new srcu_idx value.
> >>  >If srcu_idx is saved on stack this will not happen, no?
> >>
> >>  Exactly.  The case where srcu_idx is passed as a pointer parameter
> >>  is still dubious, but we can change that too.
> >>
> >But shouldn't we disallow recursive srcu lock tacking?
> 
> With different srcu_idx, nested (or overlapping) srcu is legal.

Right. If vcpu_enter_guest gets calles under a nested srcu call
we'll still get a deadlock, however.

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