Re: [Xen-devel] [PATCH 0/3] VMX: Properly handle pi descriptor and per-cpu blocking list

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Fri, 2016-06-24 at 07:59 +0000, Wu, Feng wrote:
> > -----Original Message-----
> > From: Dario Faggioli [mailto:dario.faggioli@xxxxxxxxxx]
> > So, vCPU 3 was running, but then some called stop_machine_run(),
> > which
> > causes the descheduling of vCPU 3, and the execution of the
> > stopmachine
> > tasklet.
> Thanks for your replay. Yes, I think this is point. Here descheduling
> of vCPU3
> happens, and the reason we will choose the tasklet as the next
> running
> unit for sure (not choosing another vCPU or vCPU3 itself as the next
> running unit) is because tasklet will overrides all other choose as
> stated in csched_schedule() as below, right?
> 
Exactly, tasklets preempt the running vcpu and take precedence of
runnable vcpus.

Then, in this case, the reason why we are sure that all the pcpus are
executing the body of the tasklet, is indeed the structure of
stop_machine_run() and stopmachine_action() themselves, which are built
to make sure of that, much rather than just the fact that tasklet are
higher priority.

But yes, this is what happens.

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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