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[PATCH 5/5] wil6210: fix subtle race in wil_tx_vring

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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@xxxxxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/wil6210/txrx.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/ath/wil6210/txrx.c b/drivers/net/wireless/ath/wil6210/txrx.c
index 44cdd2a..2a9d56a 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:
-- 
1.8.1.2

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