Re: [Qemu-devel] qemu vl.c

[Anders <mail@flac.kalibalik.dk>]

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?


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

and to me it seems that this might affect the case that you describe.


Cheers,
Anders.