On Wed, Jul 1, 2015 at 4:03 PM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 01/07/2015 16:59, Stefan Hajnoczi wrote:
>> I found it annoying to write it backwards too, but it's for consistency:
>>
>> if (s->buf_free_count < nb_chunks + added_chunks) {
>> trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
>> break;
>> }
>> if (IOV_MAX < nb_chunks + added_chunks) {
>> trace_mirror_break_iov_max(s, nb_chunks, added_chunks);
>> break;
>> }
>>
>> It's the same type of check as s->buf_free_count (which isn't modified
>> by this loop either so it's a yoda conditional).
>
> Hmm, right. The problem goes back to:
>
> while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
> trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
> qemu_coroutine_yield();
> }
>
> where s->buf_free_count _is_ modified by the loop. The if below:
>
> if (s->buf_free_count < nb_chunks + added_chunks) {
> trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
> break;
> }
>
> is written as a < check for consistency, and the one you add exacerbates
> the problem. If you want you can change the < to > in the "while" loop
> as well; otherwise the patch is okay as is.
Let's leave it.
