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Subject[PATCH 17/93] ath9k: fix rx descriptor related race condition
Date
3.8.13.10 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@openwrt.org>

commit e96542e55a2aacf4bdeccfe2f17b77c4895b4df2 upstream.

Similar to a race condition that exists in the tx path, the hardware
might re-read the 'next' pointer of a descriptor of the last completed
frame. This only affects non-EDMA (pre-AR93xx) devices.

To deal with this race, defer clearing and re-linking a completed rx
descriptor until the next one has been processed.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/net/wireless/ath/ath9k/ath9k.h | 5 +----
drivers/net/wireless/ath/ath9k/recv.c | 17 +++++++++++++----
2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 42794c5..46e1fa7 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -79,10 +79,6 @@ struct ath_config {
sizeof(struct ath_buf_state)); \
} while (0)

-#define ATH_RXBUF_RESET(_bf) do { \
- (_bf)->bf_stale = false; \
- } while (0)
-
/**
* enum buffer_type - Buffer type flags
*
@@ -322,6 +318,7 @@ struct ath_rx {
struct ath_buf *rx_bufptr;
struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];

+ struct ath_buf *buf_hold;
struct sk_buff *frag;
};

diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index 90752f2..262491d 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -41,8 +41,6 @@ static void ath_rx_buf_link(struct ath_softc *sc, struct ath_buf *bf)
struct ath_desc *ds;
struct sk_buff *skb;

- ATH_RXBUF_RESET(bf);
-
ds = bf->bf_desc;
ds->ds_link = 0; /* link to null */
ds->ds_data = bf->bf_buf_addr;
@@ -69,6 +67,14 @@ static void ath_rx_buf_link(struct ath_softc *sc, struct ath_buf *bf)
sc->rx.rxlink = &ds->ds_link;
}

+static void ath_rx_buf_relink(struct ath_softc *sc, struct ath_buf *bf)
+{
+ if (sc->rx.buf_hold)
+ ath_rx_buf_link(sc, sc->rx.buf_hold);
+
+ sc->rx.buf_hold = bf;
+}
+
static void ath_setdefantenna(struct ath_softc *sc, u32 antenna)
{
/* XXX block beacon interrupts */
@@ -116,7 +122,6 @@ static bool ath_rx_edma_buf_link(struct ath_softc *sc,

skb = bf->bf_mpdu;

- ATH_RXBUF_RESET(bf);
memset(skb->data, 0, ah->caps.rx_status_len);
dma_sync_single_for_device(sc->dev, bf->bf_buf_addr,
ah->caps.rx_status_len, DMA_TO_DEVICE);
@@ -444,6 +449,7 @@ int ath_startrecv(struct ath_softc *sc)
if (list_empty(&sc->rx.rxbuf))
goto start_recv;

+ sc->rx.buf_hold = NULL;
sc->rx.rxlink = NULL;
list_for_each_entry_safe(bf, tbf, &sc->rx.rxbuf, list) {
ath_rx_buf_link(sc, bf);
@@ -689,6 +695,9 @@ static struct ath_buf *ath_get_next_rx_buf(struct ath_softc *sc,
}

bf = list_first_entry(&sc->rx.rxbuf, struct ath_buf, list);
+ if (bf == sc->rx.buf_hold)
+ return NULL;
+
ds = bf->bf_desc;

/*
@@ -1238,7 +1247,7 @@ requeue:
if (edma) {
ath_rx_edma_buf_link(sc, qtype);
} else {
- ath_rx_buf_link(sc, bf);
+ ath_rx_buf_relink(sc, bf);
ath9k_hw_rxena(ah);
}
} while (1);
--
1.8.1.2


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