Re: [PATCH v3 1/2] xen/arm: vgic: Keep track of vIRQ used by a domain

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 02/02/2015 15:09, Ian Campbell wrote:
> On Thu, 2015-01-29 at 15:51 +0000, Julien Grall wrote:
>>          - Move the retry after looking for first/end. I keep the goto
>>          rather than a loop because it's more clear that we retry because
>>          we were unable to set the bit
>
> Then I think a "do {} while (!successfully allocated)" is what is
> wanted, maybe with a comment.

I though about it and I find the do {} while more difficult to read than 
the goto in this specific case.

I find more explicit with the goto that we will unlikely retry.
y. Adding a comment in the code doesn't really help.

the do {} while version would look like:

    do {
         virq = find_next_zero_bit(d->arch.vgic.allocated_irqs, end, first);
         if ( virq >= end )
             return -1;

         ret = test_and_set_bit(virq, d->arch.vgic.allocated_irqs);
         /* There is no spinlock to protect allocated_irqs, therefore
          * test_and_set_bit may unlikely fail. If so retry it.
          */
     } while ( unlikely(ret) )

Regards,

-- 
Julien Grall