On Thursday 08 April 2010 12:55:58 Bob Copeland wrote:
> As pointed out by Benoit Papillault, there is a potential
> race condition between the host and the hardware in reading
> the next link in the transmit descriptor list:
>
> cpu0 hw
> tx for buf completed
> raise tx_ok interrupt
> process buf
> buf->ds_link = 0
> read buf->ds_link
>
> This change checks txdp before processing a descriptor
> (if there are any subsequent descriptors) to see if
> hardware moved on. We'll then process this descriptor on
> the next tasklet.
>
> Signed-off-by: Bob Copeland <me@xxxxxxxxxxxxxxx>
> ---
> drivers/net/wireless/ath/ath5k/base.c | 11 +++++++++++
> 1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath5k/base.c
> b/drivers/net/wireless/ath/ath5k/base.c index 1e10439..f90c679 100644
> --- a/drivers/net/wireless/ath/ath5k/base.c
> +++ b/drivers/net/wireless/ath/ath5k/base.c
> @@ -2080,6 +2080,17 @@ ath5k_tx_processq(struct ath5k_softc *sc, struct
> ath5k_txq *txq) list_for_each_entry_safe(bf, bf0, &txq->q, list) {
> ds = bf->desc;
>
> + /*
> + * It's possible that the hardware can say the buffer is
> + * completed when it hasn't yet loaded the ds_link from
> + * host memory and moved on. If there are more TX
> + * descriptors in the queue, wait for TXDP to change
> + * before processing this one.
> + */
> + if (ath5k_hw_get_txdp(sc->ah, txq->qnum) == bf->daddr &&
> + !list_is_last(&bf->list, &txq->q))
> + break;
> +
> ret = sc->ah->ah_proc_tx_desc(sc->ah, ds, &ts);
> if (unlikely(ret == -EINPROGRESS))
> break;
for whatever it's worth :-)
Acked-by: Bruno Randolf <br1@xxxxxxxxxxx>
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