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SubjectRe: [PATCH] virtio/ringtest: fix up need_event math
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On 2017年10月26日 09:48, Michael S. Tsirkin wrote:
> last kicked event index must be updated unconditionally:
> even if we don't need to kick, we do not want to re-check
> the same entry for events.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> tools/virtio/ringtest/ring.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c
> index 6b70c4e..d044a88 100644
> --- a/tools/virtio/ringtest/ring.c
> +++ b/tools/virtio/ringtest/ring.c
> @@ -196,16 +196,18 @@ bool enable_call()
>
> void kick_available(void)
> {
> + bool need;
> +
> /* Flush in previous flags write */
> /* Barrier C (for pairing) */
> smp_mb();
> - if (!need_event(event->kick_index,
> - guest.avail_idx,
> - guest.kicked_avail_idx))
> - return;
> + need = need_event(event->kick_index,
> + guest.avail_idx,
> + guest.kicked_avail_idx);
>
> guest.kicked_avail_idx = guest.avail_idx;
> - kick();
> + if (need)
> + kick();
> }
>
> /* host side */
> @@ -265,14 +267,18 @@ bool use_buf(unsigned *lenp, void **bufp)
>
> void call_used(void)
> {
> + bool need;
> +
> /* Flush in previous flags write */
> /* Barrier D (for pairing) */
> smp_mb();
> - if (!need_event(event->call_index,
> +
> + need = !need_event(event->call_index,
> host.used_idx,
> - host.called_used_idx))
> - return;
> + host.called_used_idx);
>
> host.called_used_idx = host.used_idx;
> - call();
> +
> + if (need)
> + call();
> }

Acked-by: Jason Wang <jasowang@redhat.com>

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