Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff

[Stefan Hajnoczi]

On Thu, Jul 25, 2013 at 3:06 PM, Jan Kiszka <address@hidden> wrote:
> On 2013-07-25 15:02, Paolo Bonzini wrote:
>> Il 25/07/2013 14:48, Jan Kiszka ha scritto:
>>> The concept of clocks (with start/stop property) and active timers shall
>>> not be mixed, they are independent.
>>
>> Are you referring to this in particular:
>>
>> void pause_all_vcpus(void)
>> {
>>     CPUState *cpu = first_cpu;
>>
>>     qemu_clock_enable(vm_clock, false);
>> ...
>> }
>>
>> void resume_all_vcpus(void)
>> {
>>     CPUState *cpu = first_cpu;
>>
>>     qemu_clock_enable(vm_clock, true);
>> ...
>> }
>>
>> where _all_ the vm_clock timer lists need to be stopped at the same time?
>
> Still wrong abstraction: the vm_clock is stopped. And that implies that
> no timer using this clock will fire anymore.

Perhaps we should split QEMUClock into ClockSource and TimerList.
Instead of using the int type field in TimerList we keep a ClockSource
pointer.

A ClockSource can be enabled/disabled.

Then there's the question of ClockSource thread-safety.  Host clock is
weird because it notifies listeners when the clock source jumps.  vm
clock is hard because of icount.

It's also weird to think about multiple threads dispatching timer
callbacks while a ClockSource is disabled.  Basically, do we need a
guarantee that timer callbacks have completed and will not be invoked
in any thread after the disable function returns?

But assuming thread-safety is addressed, this would fit the design
you're suggesting.

Stefan