Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966298Ab0BZVic (ORCPT ); Fri, 26 Feb 2010 16:38:32 -0500 Received: from mail.dev.rtsoft.ru ([213.79.90.226]:34697 "HELO mail.dev.rtsoft.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S966287Ab0BZVi2 (ORCPT ); Fri, 26 Feb 2010 16:38:28 -0500 Date: Sat, 27 Feb 2010 00:38:25 +0300 From: Anton Vorontsov To: Paul Gortmaker Cc: Martyn Welch , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev list , Sandeep Gopalpet , davem@davemloft.net Subject: Re: Gianfar driver failing on MPC8641D based board Message-ID: <20100226213825.GA32363@oksana.dev.rtsoft.ru> Reply-To: avorontsov@ru.mvista.com References: <20100225174935.GA32370@oksana.dev.rtsoft.ru> <7d1d9c251002251653n6473f01ex2d43933ec6aa010b@mail.gmail.com> <20100226031452.GA11319@oksana.dev.rtsoft.ru> <4B87B937.6010204@ge.com> <20100226143532.GA31622@oksana.dev.rtsoft.ru> <4B87E01E.4070704@windriver.com> <4B87E662.3080106@ge.com> <4B87E9EF.3010604@ge.com> <20100226161058.GA22954@oksana.dev.rtsoft.ru> <4B87F67E.5070601@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4B87F67E.5070601@windriver.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4229 Lines: 96 On Fri, Feb 26, 2010 at 11:27:42AM -0500, Paul Gortmaker wrote: > On 10-02-26 11:10 AM, Anton Vorontsov wrote: > > On Fri, Feb 26, 2010 at 03:34:07PM +0000, Martyn Welch wrote: > > [...] > >> Out of 10 boot attempts, 7 failed. > > > > OK, I see why. With ip=on (dhcp boot) it's much harder to trigger > > it. With static ip config can I see the same. > > I'd kind of expected to see us stuck in gianfar on that lock, but > the SysRQ-T doesn't show us hung up anywhere in gianfar itself. > [This was on a base 2.6.33, with just a small sysrq fix patch] > [df841a30] [c0009fc4] __switch_to+0x8c/0xf8 > [df841a50] [c0350160] schedule+0x354/0x92c > [df841ae0] [c0331394] rpc_wait_bit_killable+0x2c/0x54 > [df841af0] [c0350eb0] __wait_on_bit+0x9c/0x108 > [df841b10] [c0350fc0] out_of_line_wait_on_bit+0xa4/0xb4 > [df841b40] [c0331cf0] __rpc_execute+0x16c/0x398 > [df841b90] [c0329abc] rpc_run_task+0x48/0x9c > [df841ba0] [c0329c40] rpc_call_sync+0x54/0x88 > [df841bd0] [c015e780] nfs_proc_lookup+0x94/0xe8 > [df841c20] [c014eb60] nfs_lookup+0x12c/0x230 > [df841d50] [c00b9680] do_lookup+0x118/0x288 > [df841d80] [c00bb904] link_path_walk+0x194/0x1118 > [df841df0] [c00bcb08] path_walk+0x8c/0x168 > [df841e20] [c00bcd6c] do_path_lookup+0x74/0x7c > [df841e40] [c00be148] do_filp_open+0x5d4/0xba4 > [df841f10] [c00abe94] do_sys_open+0xac/0x190 Yeah, I don't think this is gianfar-related. It must be something else triggered by the fact that gianfar no longer sends stuff. OK, I think I found what's happening in gianfar. Some background... 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. It works flawlessly on my p2020, please try it. Thanks! 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) & -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/