From patchwork Wed Mar 3 18:18:58 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Vorontsov X-Patchwork-Id: 46853 X-Patchwork-Delegate: galak@kernel.crashing.org Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from bilbo.ozlabs.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 8CD80B7F90 for ; Thu, 4 Mar 2010 05:19:12 +1100 (EST) Received: by ozlabs.org (Postfix) id 661CBB7D0A; Thu, 4 Mar 2010 05:19:03 +1100 (EST) Delivered-To: linuxppc-dev@ozlabs.org Received: from mail.dev.rtsoft.ru (mail.dev.rtsoft.ru [213.79.90.226]) by ozlabs.org (Postfix) with SMTP id 13710B7D27 for ; Thu, 4 Mar 2010 05:19:01 +1100 (EST) Received: (qmail 9175 invoked from network); 3 Mar 2010 18:19:05 -0000 Received: from unknown (HELO localhost) (192.168.1.70) by 0 with SMTP; 3 Mar 2010 18:19:05 -0000 Date: Wed, 3 Mar 2010 21:18:58 +0300 From: Anton Vorontsov To: David Miller Subject: [PATCH] gianfar: Fix TX ring processing on SMP machines Message-ID: <20100303181858.GA458@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Cc: linuxppc-dev@ozlabs.org, netdev@vger.kernel.org, Martyn Welch , Paul Gortmaker , Sandeep Gopalpet X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org 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. Reported-by: Martyn Welch Bisected-by: Paul Gortmaker Signed-off-by: Anton Vorontsov Tested-by: Paul Gortmaker Tested-by: Martyn Welch Cc: Sandeep Gopalpet Cc: Stable [2.6.33] --- drivers/net/gianfar.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c index 8bd3c9f..cccb409 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) &