Re: [Qemu-devel] [RFC v2 3/5] timer: make qemu_clock_enable sync between disable and timer's cb

[liu ping fan]

On Fri, Aug 2, 2013 at 10:43 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Fri, Aug 02, 2013 at 11:33:40AM +0800, liu ping fan wrote:
>> On Thu, Aug 1, 2013 at 9:28 PM, Alex Bligh <address@hidden> wrote:
>> > Paolo,
>> >
>> >
>> > --On 1 August 2013 08:19:34 -0400 Paolo Bonzini <address@hidden> wrote:
>> >
>> >>> > True, qemu_event basically works only when a single thread resets it.
>> >>> > But there is no race condition here because qemu_run_timers cannot be
>> >>> > executed concurrently by multiple threads (like aio_poll in your
>> >>> > bottom half patches).
>> >>>
>> >>> ... or, if rebasing on top of my patches, qemu_run_timers *can* be
>> >>> executed concurrently by mulitple threads, but in respect of any given
>> >>> QEMUTimerList, it will only be executed by one thread.
>> >>
>> >>
>> >> ... so the event would be placed in QEMUTimerList, not QEMUClock.
>> >
>> >
>> > Correct
>> >
>> >
>> >> qemu_clock_enable then will have to visit all timer lists. That's
>> >> not hard to do,
>> >
>> >
>> > Correct, v4 of my patch does this.
>> >
>> >
>> >> but as locks proliferate we need to have a clear
>> >> policy (e.g. BQL -> clock -> timerlist).
>> >
>> >
>> > But doesn't do the locking bit yet (Pingfan is going to do that I hope)
>> >
>> Seem that Stefanha had been involved in this, and sent out his patches :)
>
> Hi Ping Fan,
> I dropped the series where I added locks to qemu-timer.c from a few
> weeks ago.
>
> With your series rebased onto Alex's series, I think my patches are no
> longer needed?
>
No. The active_timers list which is still touched by
qemu_mod_timer_ns() needs protection between vcpu/iothread/..
I think you want to pick up your patches?

Regards,
Pingfan