wil6210: fix subtle race in wil_tx_vring

Finish all SW context modifications prior to notifying hardware

It used to be race condition: if HW finish Tx and issue Tx completion IRQ very fast,
prior to SW context update in wil_tx_vring, Tx completion will mis-handle descriptor, as
SW part will have no skb pointer stored.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/net/wireless/ath/wil6210/txrx.c b/drivers/net/wireless/ath/wil6210/txrx.c
index 44cdd2a3dff3..2a9d56a5fd0c 100644
--- a/drivers/net/wireless/ath/wil6210/txrx.c
+++ b/drivers/net/wireless/ath/wil6210/txrx.c
@@ -712,6 +712,12 @@ static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
         d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_DMA_IT_POS);
         *_d = *d;
 
+        /* hold reference to skb
+         * to prevent skb release before accounting
+         * in case of immediate "tx done"
+         */
+        vring->ctx[i].skb = skb_get(skb);
+
         wil_hex_dump_txrx("Tx ", DUMP_PREFIX_NONE, 32, 4,
                           (const void *)d, sizeof(*d), false);
 
@@ -720,11 +726,6 @@ static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
         wil_dbg_txrx(wil, "Tx swhead %d -> %d\n", swhead, vring->swhead);
         trace_wil6210_tx(vring_index, swhead, skb->len, nr_frags);
         iowrite32(vring->swhead, wil->csr + HOSTADDR(vring->hwtail));
-        /* hold reference to skb
-         * to prevent skb release before accounting
-         * in case of immediate "tx done"
-         */
-        vring->ctx[i].skb = skb_get(skb);
 
         return 0;
  dma_error: