Re: [Qemu-devel] qemu vl.c

[Paul Brook]

On Sunday 16 December 2007, Anders wrote:
> Paul Brook wrote:
> >>    Redundant timer rearm optimisation by Anders Melchiorsen.
> >
> > I think this is incorrect.
> >
> > When a timer is modified, we need to rearm the host timer immediately. We
> > can not wait for the old timer to fire, or for execution to fall back to
> > the main_loop_wait.  Consider the case where the guest adds a timer
> > interrupt and immediately enters a tight loop - Quite a common operation
> > when calibrating a software delay loop. The timer won't be rearmed until
> > some other event occurs. It the system is otherwise quiescent and you're
> > not using SDL output it may never occur.
>
> Hi Paul,
>
> I am certainly open to it not being correct, but currently I fail to see
> how it changes the scenario that you mention. The rearming is moved away
> from qemu_run_timers(), not qemu_mod_timer(). Can you elaborate?

It's possible that this code has always been broken. You changes make it much 
more obviously so.

> There was a previous patch to remove the rearming when timers are modified,
>
> http://cvs.savannah.gnu.org/viewvc/qemu/vl.c?root=qemu&view=log#rev1.345

I think this this is unrealted.