[Qemu-devel] Re: [PATCH 11/19] use a bottom half to run timers

[Anthony Liguori]

On 01/04/2010 02:01 PM, Michael S. Tsirkin wrote:
> On Mon, Jan 04, 2010 at 02:24:53PM -0600, Anthony Liguori wrote:
>    
> > On 12/21/2009 02:09 AM, Paolo Bonzini wrote:
> >      
> > > Make the timer subsystem register its own bottom half instead of
> > > placing the bottom half code in the heart of the main loop.  To
> > > test if an alarm timer is pending, just check if the bottom half is
> > > scheduled.
> > >
> > > Signed-off-by: Paolo Bonzini<address@hidden>
> > >        
> > I'm not a huge fan of this for a couple reasons.  The first is that it
> > introduces a subtle semantic change.  Previously, timers always ran
> > before bottom halves whereas after this change, timers may run after
> > some bottoms halves but before others.  While this should be okay in
> > principle, in practice, I'm sure it'll introduce regressions.  I'd be
> > very surprised if cris wasn't affected by this.
> >
> > But more importantly, I think timer dispatch needs to be part of the
> > select loop.  malc has a git tree that replaces host alarm timers with
> > select() timeouts.
> >      
> Where is that tree?
>    

http://repo.or.cz/w/qemu/malc.git  mtloop

> IMO we need that, I am not sure all code is as signal-safe
> as it should be. At least crashes that I saw with winxp install
> seem to be related to signal handling.
>    

Regards,

Anthony Liguori