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authorAnton Vorontsov <avorontsov@ru.mvista.com>2010-03-03 08:18:58 +0000
committerThomas Gleixner <tglx@linutronix.de>2010-06-23 17:36:11 +0200
commit42edbcbc3240b56cf89a426cbfe9c8d9051459c4 (patch)
parentfaf35813f204901f85dd0c6b3c5092e0064c6c2f (diff)
gianfar: Fix TX ring processing on SMP machines
Starting with commit a3bc1f11e9b867a4f49505 ("gianfar: Revive SKB recycling") gianfar driver sooner or later stops transmitting any packets on SMP machines. start_xmit() prepares new skb for transmitting, generally it does three things: 1. sets up all BDs (marks them ready to send), except the first one. 2. stores skb into tx_queue->tx_skbuff so that clean_tx_ring() would cleanup it later. 3. sets up the first BD, i.e. marks it ready. Here is what clean_tx_ring() does: 1. reads skbs from tx_queue->tx_skbuff 2. checks if the *last* BD is ready. If it's still ready [to send] then it it isn't transmitted, so clean_tx_ring() returns. Otherwise it actually cleanups BDs. All is OK. Now, if there is just one BD, code flow: - start_xmit(): stores skb into tx_skbuff. Note that the first BD (which is also the last one) isn't marked as ready, yet. - clean_tx_ring(): sees that skb is not null, *and* its lstatus says that it is NOT ready (like if BD was sent), so it cleans it up (bad!) - start_xmit(): marks BD as ready [to send], but it's too late. We can fix this simply by reordering lstatus/tx_skbuff writes. [ Upstream commit: 0eddba525cf4c3a4aab9feaf36b12b465290d4a7 ] Reported-by: Martyn Welch <martyn.welch@ge.com> Bisected-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com> Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com> Tested-by: Martyn Welch <martyn.welch@ge.com> Cc: Sandeep Gopalpet <Sandeep.Kumar@freescale.com> Cc: Stable <stable@vger.kernel.org> [2.6.33] Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index 5c8594891008..f819db24aef6 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -2021,7 +2021,6 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
/* setup the TxBD length and buffer pointer for the first BD */
- tx_queue->tx_skbuff[tx_queue->skb_curtx] = skb;
txbdp_start->bufPtr = dma_map_single(&priv->ofdev->dev, skb->data,
skb_headlen(skb), DMA_TO_DEVICE);
@@ -2053,6 +2052,10 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
txbdp_start->lstatus = lstatus;
+ eieio(); /* force lstatus write before tx_skbuff */
+ tx_queue->tx_skbuff[tx_queue->skb_curtx] = skb;
/* Update the current skb pointer to the next entry we will use
* (wrapping if necessary) */
tx_queue->skb_curtx = (tx_queue->skb_curtx + 1) &