Re: [PATCH 1/6] mac802154: Immediately retry sending failed packets

[Alexander Smirnov <alex.bluesman.smirnov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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2013/4/2 Alan Ott <alan-yzvJWuRpmD1zbRFIqnYvSA@public.gmane.org>

> When ops->xmit() fails, immediately retry. Previously the packet was sent
> to the back of the workqueue.
>
> Signed-off-by: Alan Ott <alan-yzvJWuRpmD1zbRFIqnYvSA@public.gmane.org>
> ---
>  net/mac802154/tx.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
> index 4e09d07..fbf937c 100644
> --- a/net/mac802154/tx.c
> +++ b/net/mac802154/tx.c
> @@ -59,19 +59,18 @@ static void mac802154_xmit_worker(struct work_struct
> *work)
>                 }
>         }
>
> -       res = xw->priv->ops->xmit(&xw->priv->hw, xw->skb);
> +       do {
> +               res = xw->priv->ops->xmit(&xw->priv->hw, xw->skb);
> +               if (res && ++xw->xmit_attempts >=
> MAC802154_MAX_XMIT_ATTEMPTS) {
> +                       pr_debug("transmission failed for %d times",
> +                                MAC802154_MAX_XMIT_ATTEMPTS);
> +                       break;
> +               }
> +       } while (res);
>


> IIRC this 802.15.4 stack uses single-thread-work-queue and all RX/TX are
> performed by using it. Doing TX retry in the way you proposed - it's
> possible that you will block other packets pending in this queue. Despite
> on Linux is already 'slow' system to provide real-time for specific
> 802.15.4 features, I think it's not a good idea to increase nodes
> communication latency.
>
>
>  out:
>         mutex_unlock(&xw->priv->phy->pib_lock);
>
> -       if (res) {
> -               if (xw->xmit_attempts++ < MAC802154_MAX_XMIT_ATTEMPTS) {
> -                       queue_work(xw->priv->dev_workqueue, &xw->work);
> -                       return;
> -               } else
> -                       pr_debug("transmission failed for %d times",
> -                                MAC802154_MAX_XMIT_ATTEMPTS);
> -       }
>
>         dev_kfree_skb(xw->skb);
>
> --
> 1.7.11.2
>
>

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