Re: [PATCH v3 1/3] Introduce a workqueue to deliver PIT timer interrupts.

[Avi Kivity <avi@redhat.com>]

On 04/16/2012 07:33 PM, Jan Kiszka wrote:
> On 2010-06-16 23:11, Chris Lalancette wrote:
> > We really want to "kvm_set_irq" during the hrtimer callback,
> > but that is risky because that is during interrupt context.
> > Instead, offload the work to a workqueue, which is a bit safer
> > and should provide most of the same functionality.
>
> Unfortunately, workqueues do not have fixed kthread associations (and
> "kvm-pit-wq" would be too unspecific when running multiple VMs). So I
> just realized that this subtly breaks the ability to run KVM guests with
> RT priority (boot managers with timeouts hang as the workqueue starves).
>
> Before throwing some kthread_worker at this, could someone help me
> recalling what was "risky" here? That the PIT IRQ may have to be
> broadcast to a large number of VCPUs? 

(or any irq, once we make that function irq safe)

> I would offer to include this
> information in my changelog. ;)

That, plus the need to make all the .set methods safe in that context.

-- 
error compiling committee.c: too many arguments to function