Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030414AbWJJVOi (ORCPT ); Tue, 10 Oct 2006 17:14:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030413AbWJJVOh (ORCPT ); Tue, 10 Oct 2006 17:14:37 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:34996 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1030406AbWJJVOg (ORCPT ); Tue, 10 Oct 2006 17:14:36 -0400 Date: Tue, 10 Oct 2006 16:14:29 -0500 To: akpm@osdl.org Cc: jeff@garzik.org, Arnd Bergmann , netdev@vger.kernel.org, James K Lewis , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org Subject: [PATCH 15/21]: powerpc/cell spidernet refine locking Message-ID: <20061010211429.GL4381@austin.ibm.com> References: <20061010204946.GW4381@austin.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061010204946.GW4381@austin.ibm.com> User-Agent: Mutt/1.5.11 From: linas@austin.ibm.com (Linas Vepstas) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7269 Lines: 239 The transmit side of the spider ethernet driver currently places locks around some very large chunks of code. This results in a fair amount of lock contention is some cases. This patch makes the locks much more fine-grained, protecting only the cirtical sections. One lock is used to protect three locations: the queue head and tail pointers, and the queue low-watermark location. Signed-off-by: Linas Vepstas Cc: Arnd Bergmann Cc: James K Lewis ---- drivers/net/spider_net.c | 95 +++++++++++++++++++++-------------------------- 1 file changed, 43 insertions(+), 52 deletions(-) Index: linux-2.6.18-mm2/drivers/net/spider_net.c =================================================================== --- linux-2.6.18-mm2.orig/drivers/net/spider_net.c 2006-10-10 13:10:37.000000000 -0500 +++ linux-2.6.18-mm2/drivers/net/spider_net.c 2006-10-10 13:20:08.000000000 -0500 @@ -646,8 +646,9 @@ static int spider_net_prepare_tx_descr(struct spider_net_card *card, struct sk_buff *skb) { - struct spider_net_descr *descr = card->tx_chain.head; + struct spider_net_descr *descr; dma_addr_t buf; + unsigned long flags; int length; length = skb->len; @@ -666,6 +667,10 @@ spider_net_prepare_tx_descr(struct spide return -ENOMEM; } + spin_lock_irqsave(&card->tx_chain.lock, flags); + descr = card->tx_chain.head; + card->tx_chain.head = descr->next; + descr->buf_addr = buf; descr->buf_size = length; descr->next_descr_addr = 0; @@ -674,6 +679,8 @@ spider_net_prepare_tx_descr(struct spide descr->dmac_cmd_status = SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS; + spin_unlock_irqrestore(&card->tx_chain.lock, flags); + if (skb->protocol == htons(ETH_P_IP)) switch (skb->nh.iph->protocol) { case IPPROTO_TCP: @@ -691,42 +698,17 @@ spider_net_prepare_tx_descr(struct spide return 0; } -/** - * spider_net_release_tx_descr - processes a used tx descriptor - * @card: card structure - * @descr: descriptor to release - * - * releases a used tx descriptor (unmapping, freeing of skb) - */ -static inline void -spider_net_release_tx_descr(struct spider_net_card *card) -{ - struct spider_net_descr *descr = card->tx_chain.tail; - struct sk_buff *skb; - unsigned int len; - - card->tx_chain.tail = card->tx_chain.tail->next; - descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE; - - /* unmap the skb */ - skb = descr->skb; - if (!skb) - return; - len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len; - pci_unmap_single(card->pdev, descr->buf_addr, len, - PCI_DMA_TODEVICE); - dev_kfree_skb(skb); -} - static void spider_net_set_low_watermark(struct spider_net_card *card) { + unsigned long flags; int status; int cnt=0; int i; struct spider_net_descr *descr = card->tx_chain.tail; - /* Measure the length of the queue. */ + /* Measure the length of the queue. Measurement does not + * need to be precise -- does not need a lock. */ while (descr != card->tx_chain.head) { status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE; if (status == SPIDER_NET_DESCR_NOT_IN_USE) @@ -746,11 +728,13 @@ spider_net_set_low_watermark(struct spid descr = descr->next; /* Set the new watermark, clear the old watermark */ + spin_lock_irqsave(&card->tx_chain.lock, flags); descr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG; if (card->low_watermark && card->low_watermark != descr) card->low_watermark->dmac_cmd_status = card->low_watermark->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG; card->low_watermark = descr; + spin_unlock_irqrestore(&card->tx_chain.lock, flags); } /** @@ -769,21 +753,31 @@ static int spider_net_release_tx_chain(struct spider_net_card *card, int brutal) { struct spider_net_descr_chain *chain = &card->tx_chain; + struct spider_net_descr *descr; + struct sk_buff *skb; + u32 buf_addr; + unsigned long flags; int status; spider_net_read_reg(card, SPIDER_NET_GDTDMACCNTR); while (chain->tail != chain->head) { - status = spider_net_get_descr_status(chain->tail); + spin_lock_irqsave(&chain->lock, flags); + descr = chain->tail; + + status = spider_net_get_descr_status(descr); switch (status) { case SPIDER_NET_DESCR_COMPLETE: card->netdev_stats.tx_packets++; - card->netdev_stats.tx_bytes += chain->tail->skb->len; + card->netdev_stats.tx_bytes += descr->skb->len; break; case SPIDER_NET_DESCR_CARDOWNED: - if (!brutal) + if (!brutal) { + spin_unlock_irqrestore(&chain->lock, flags); return 1; + } + /* fallthrough, if we release the descriptors * brutally (then we don't care about * SPIDER_NET_DESCR_CARDOWNED) */ @@ -800,12 +794,25 @@ spider_net_release_tx_chain(struct spide default: card->netdev_stats.tx_dropped++; - if (!brutal) + if (!brutal) { + spin_unlock_irqrestore(&chain->lock, flags); return 1; + } } - spider_net_release_tx_descr(card); - } + chain->tail = descr->next; + descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE; + skb = descr->skb; + buf_addr = descr->buf_addr; + spin_unlock_irqrestore(&chain->lock, flags); + + /* unmap the skb */ + if (skb) { + int len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len; + pci_unmap_single(card->pdev, buf_addr, len, PCI_DMA_TODEVICE); + dev_kfree_skb(skb); + } + } return 0; } @@ -857,27 +864,19 @@ spider_net_xmit(struct sk_buff *skb, str { struct spider_net_card *card = netdev_priv(netdev); struct spider_net_descr_chain *chain = &card->tx_chain; - struct spider_net_descr *descr = chain->head; - unsigned long flags; - - spin_lock_irqsave(&chain->lock, flags); spider_net_release_tx_chain(card, 0); if ((chain->head->next == chain->tail->prev) || - (spider_net_get_descr_status(descr) != SPIDER_NET_DESCR_NOT_IN_USE) || (spider_net_prepare_tx_descr(card, skb) != 0)) { card->netdev_stats.tx_dropped++; - spin_unlock_irqrestore(&chain->lock, flags); netif_stop_queue(netdev); return NETDEV_TX_BUSY; } spider_net_set_low_watermark(card); spider_net_kick_tx_dma(card); - card->tx_chain.head = card->tx_chain.head->next; - spin_unlock_irqrestore(&chain->lock, flags); return NETDEV_TX_OK; } @@ -893,16 +892,11 @@ spider_net_xmit(struct sk_buff *skb, str static void spider_net_cleanup_tx_ring(struct spider_net_card *card) { - unsigned long flags; - - spin_lock_irqsave(&card->tx_chain.lock, flags); - if ((spider_net_release_tx_chain(card, 0) != 0) && (card->netdev->flags & IFF_UP)) { spider_net_kick_tx_dma(card); netif_wake_queue(card->netdev); } - spin_unlock_irqrestore(&card->tx_chain.lock, flags); } /** @@ -1930,10 +1924,7 @@ spider_net_stop(struct net_device *netde spider_net_disable_rxdmac(card); /* release chains */ - if (spin_trylock(&card->tx_chain.lock)) { - spider_net_release_tx_chain(card, 1); - spin_unlock(&card->tx_chain.lock); - } + spider_net_release_tx_chain(card, 1); spider_net_free_chain(card, &card->tx_chain); spider_net_free_chain(card, &card->rx_chain); - 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/