Re: [Xen-devel] [PATCH v5 04/10] xen/arm: support HW interrupts, do not request maintenance_interrupts

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-03-24 at 18:49 +0000, Stefano Stabellini wrote:
>  
> +static void gic_clear_one_lr(struct vcpu *v, int i)
> +{
> +    struct pending_irq *p;
> +    uint32_t lr;
> +    int irq;
> +    bool_t inflight;
> +
> +    ASSERT(!local_irq_is_enabled());
> +    ASSERT(spin_is_locked(&v->arch.vgic.lock));
[...]
> +        if ( !inflight )
> +        {
> +            spin_lock(&v->arch.vgic.lock);

Aren't you recursively taking this lock here?

In principal could you remove the requirement for the caller to hold
this lock as long as you took it just before p = irq_to_pending(v, irq);
and released it on each iteration? (I'm not at all sure of that, just
wondering)

> +            list_del_init(&p->inflight);
> +            spin_unlock(&v->arch.vgic.lock);
> +        }
> +    }
> +}
> +
> +void gic_clear_lrs(struct vcpu *v)
> +{
> +    int i = 0;
> +    unsigned long flags;
> +
> +    spin_lock_irqsave(&v->arch.vgic.lock, flags);
> +
> +    while ((i = find_next_bit((const unsigned long *) &this_cpu(lr_mask),
> +                              nr_lrs, i)) < nr_lrs) {
> +        gic_clear_one_lr(v, i);
> +        i++;
> +    }
> +
> +    spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
> +}
> +
>  static void gic_restore_pending_irqs(struct vcpu *v)
>  {
>      int i;
[...]

> +    /* 
> +     * The maintenance interrupt handler doesn't do anything anymore, but

"This is a dummy interrupt handler." (We don't care about "anymore" once
this is applied

> +     * receiving the interrupt is going to cause gic_inject to be called on

          Receiving... (because of the full stop I added above)

> @@ -1642,6 +1647,11 @@ asmlinkage void leave_hypervisor_tail(void)
>      }
>  }
>  
> +static void enter_hypervisor_head(void)
> +{
> +    gic_clear_lrs(current);
> +}

Just put it before the first use and avoid the need for the forward
declaration.

Ian.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel