From: Linas Vepstas Date: Tue, 10 Oct 2006 21:14:29 +0000 (-0500) Subject: [PATCH] powerpc/cell spidernet refine locking X-Git-Tag: v2.6.19-rc2~23^2~12 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=9cc7bf7edf50a8a6b456b337aff97fe780ae369b;p=linux-2.6-omap-h63xx.git [PATCH] powerpc/cell spidernet refine locking 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 Signed-off-by: Jeff Garzik --- diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c index e429abc1e94..f8d7d0d91a6 100644 --- a/drivers/net/spider_net.c +++ b/drivers/net/spider_net.c @@ -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 spider_net_card *card, 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 spider_net_card *card, 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 spider_net_card *card, 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 spider_net_card *card) 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 spider_net_card *card, int brutal) 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, struct net_device *netdev) { 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, struct net_device *netdev) 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 *netdev) 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);