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

[malc]

On Tue, 5 Jan 2010, Michael S. Tsirkin wrote:

> On Tue, Jan 05, 2010 at 06:23:34PM +0300, malc wrote:
> > On Tue, 5 Jan 2010, Michael S. Tsirkin wrote:
> > 
> > > On Mon, Jan 04, 2010 at 05:54:13PM -0600, Anthony Liguori wrote:
> > > > 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
> > > 
> > > Don't seem to see anything there.
> > > malc?
> > 
> > Yes?
> 
> Do you have a patch to switch from signals to select?  If yes could you
> tell me where it is so  I can test whether it fixes winxp install
> crashes I see?

All i have is published at:
http://repo.or.cz/w/qemu/malc.git/shortlog/refs/heads/mtloop

Specifically:
http://repo.or.cz/w/qemu/malc.git/commit/b99fef4dc2f1ce9d436791b6821cb30e6335ee9b

A small fix is needed to make it run with KVM though.

> 
> > > >> 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
> > > 
> > 
> > -- 
> > mailto:address@hidden
> 

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