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

[Avi Kivity <avi@redhat.com>]

On 06/08/2010 08:55 PM, 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.
>
>
>
>
> +static void pit_do_work(struct work_struct *work)
> +{
> +       struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
> +       struct kvm *kvm = pit->kvm;
> +       struct kvm_vcpu *vcpu;
> +       int i;
> +       struct kvm_kpit_state *ps =&pit->pit_state;
> +       int inject = 0;
> +
> +       /* Try to inject pending interrupts when
> +        * last one has been acked.
> +        */
> +       raw_spin_lock(&ps->inject_lock);
> +       if (ps->irq_ack) {
> +               ps->irq_ack = 0;
> +               inject = 1;
> +       }
> +       raw_spin_unlock(&ps->inject_lock);
>    

I don't think this needs to be a raw spinlock any longer (a nice side 
effect).+
> +static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
> +{
> +       struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
> +       struct kvm_pit *pt = ktimer->kvm->arch.vpit;
> +
> +       queue_work(pit_wq,&pt->expired);
> +
> +       if (ktimer->t_ops->is_periodic(ktimer)) {
> +               hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
>    

spaces/tabs

> +              return HRTIMER_RESTART;
> +       }
> +       else
> +              return HRTIMER_NORESTART;
> +}
> +
>    

Somewhere, you have to cancel a pending work struct.  At least during 
destruction, but perhaps also if the pit is configured not to generate 
interrupts any more.

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