ath9k: fix an rx descriptor processing race condition

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 37746

package/kernel/mac80211/patches/556-ath9k_fix_rx_race.patch

@@ -0,0 +1,82 @@
+--- 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
+  *
+@@ -315,6 +311,7 @@ struct ath_rx {
+ 	struct ath_descdma rxdma;
+ 	struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];
+ 
++	struct ath_buf *buf_hold;
+ 	struct sk_buff *frag;
+ 
+ 	u32 ampdu_ref;
+--- a/drivers/net/wireless/ath/ath9k/recv.c
++++ b/drivers/net/wireless/ath/ath9k/recv.c
+@@ -42,8 +42,6 @@ static void ath_rx_buf_link(struct ath_s
+ 	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;
+@@ -70,6 +68,14 @@ static void ath_rx_buf_link(struct ath_s
+ 	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 */
+@@ -117,7 +123,6 @@ static bool ath_rx_edma_buf_link(struct 
+ 
+ 	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);
+@@ -432,6 +437,7 @@ 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);
+@@ -677,6 +683,9 @@ static struct ath_buf *ath_get_next_rx_b
+ 	}
+ 
+ 	bf = list_first_entry(&sc->rx.rxbuf, struct ath_buf, list);
++	if (bf == sc->rx.buf_hold)
++		return NULL;
++
+ 	ds = bf->bf_desc;
+ 
+ 	/*
+@@ -1391,7 +1400,7 @@ 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);