From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tina Yang Subject: Re: [PATCH] add netconsole support for xen-netfront Date: Tue, 17 Jan 2012 13:42:22 -0800 Message-ID: <4F15EB3E.3060700@oracle.com> References: <1326271956-25565-1-git-send-email-zhenzhong.duan@oracle.com> <20120112141745.GA7685@phenom.dumpdata.com> <1326452769.17210.331.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Konrad Rzeszutek Wilk , Zhenzhong Duan , "xen-devel@lists.xensource.com" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "gurudas.pai@oracle.com" , Jeremy Fitzhardinge To: Ian Campbell Return-path: In-Reply-To: <1326452769.17210.331.camel@zakaz.uk.xensource.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 1/13/2012 3:06 AM, Ian Campbell wrote: > On Thu, 2012-01-12 at 14:17 +0000, Konrad Rzeszutek Wilk wrote: >> On Wed, Jan 11, 2012 at 04:52:36PM +0800, Zhenzhong Duan wrote: >>> add polling interface to xen-netfront device to support netconsole >>> >> Ian, any thoughts on the spinlock changes? > What are they for? When I did this patch back in 2008, both netconsole and netdump were supported. Spin_lock w/o irqsave and irqrestore would cause netdump hang due to the unexpected change of the irq status. Although netdump is now obsolete, I think it's always a good practice to preserve caller's irq status as we had a very bad experience chasing a similar problem caused by such a irq change in RDS in the not too long ago past. > At a guess they are a necessary consequence of the new calling context. > However not all the drivers I looked at which supported netpool were > using the irqsave variants in this context so I guess it must be some > secondary effect. > > Anyway, the upshot is that I think the changelog needs to explain the > rationale for the locking change. > > Ian. > >>> Signed-off-by: Tina.Yang >>> Cc: Konrad Rzeszutek Wilk >>> Cc: Jeremy Fitzhardinge >>> Signed-off-by: Zhenzhong.Duan >>> Tested-by: gurudas.pai >>> --- >>> drivers/net/xen-netfront.c | 57 ++++++++++++++++++++++++++----------------- >>> 1 files changed, 34 insertions(+), 23 deletions(-) >>> >>> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c >>> index fa67905..db638b4 100644 >>> --- a/drivers/net/xen-netfront.c >>> +++ b/drivers/net/xen-netfront.c >>> @@ -489,6 +489,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) >>> int frags = skb_shinfo(skb)->nr_frags; >>> unsigned int offset = offset_in_page(data); >>> unsigned int len = skb_headlen(skb); >>> + unsigned long flags; >>> >>> frags += DIV_ROUND_UP(offset + len, PAGE_SIZE); >>> if (unlikely(frags> MAX_SKB_FRAGS + 1)) { >>> @@ -498,12 +499,12 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) >>> goto drop; >>> } >>> >>> - spin_lock_irq(&np->tx_lock); >>> + spin_lock_irqsave(&np->tx_lock, flags); >>> >>> if (unlikely(!netif_carrier_ok(dev) || >>> (frags> 1&& !xennet_can_sg(dev)) || >>> netif_needs_gso(skb, netif_skb_features(skb)))) { >>> - spin_unlock_irq(&np->tx_lock); >>> + spin_unlock_irqrestore(&np->tx_lock, flags); >>> goto drop; >>> } >>> >>> @@ -574,7 +575,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) >>> if (!netfront_tx_slot_available(np)) >>> netif_stop_queue(dev); >>> >>> - spin_unlock_irq(&np->tx_lock); >>> + spin_unlock_irqrestore(&np->tx_lock, flags); >>> >>> return NETDEV_TX_OK; >>> >>> @@ -1228,6 +1229,33 @@ static int xennet_set_features(struct net_device *dev, >>> return 0; >>> } >>> >>> +static irqreturn_t xennet_interrupt(int irq, void *dev_id) >>> +{ >>> + struct net_device *dev = dev_id; >>> + struct netfront_info *np = netdev_priv(dev); >>> + unsigned long flags; >>> + >>> + spin_lock_irqsave(&np->tx_lock, flags); >>> + >>> + if (likely(netif_carrier_ok(dev))) { >>> + xennet_tx_buf_gc(dev); >>> + /* Under tx_lock: protects access to rx shared-ring indexes. */ >>> + if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx)) >>> + napi_schedule(&np->napi); >>> + } >>> + >>> + spin_unlock_irqrestore(&np->tx_lock, flags); >>> + >>> + return IRQ_HANDLED; >>> +} >>> + >>> +#ifdef CONFIG_NET_POLL_CONTROLLER >>> +static void xennet_poll_controller(struct net_device *dev) >>> +{ >>> + xennet_interrupt(0, dev); >>> +} >>> +#endif >>> + >>> static const struct net_device_ops xennet_netdev_ops = { >>> .ndo_open = xennet_open, >>> .ndo_uninit = xennet_uninit, >>> @@ -1239,6 +1267,9 @@ static const struct net_device_ops xennet_netdev_ops = { >>> .ndo_validate_addr = eth_validate_addr, >>> .ndo_fix_features = xennet_fix_features, >>> .ndo_set_features = xennet_set_features, >>> +#ifdef CONFIG_NET_POLL_CONTROLLER >>> + .ndo_poll_controller = xennet_poll_controller, >>> +#endif >>> }; >>> >>> static struct net_device * __devinit xennet_create_dev(struct xenbus_device *dev) >>> @@ -1448,26 +1479,6 @@ static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[]) >>> return 0; >>> } >>> >>> -static irqreturn_t xennet_interrupt(int irq, void *dev_id) >>> -{ >>> - struct net_device *dev = dev_id; >>> - struct netfront_info *np = netdev_priv(dev); >>> - unsigned long flags; >>> - >>> - spin_lock_irqsave(&np->tx_lock, flags); >>> - >>> - if (likely(netif_carrier_ok(dev))) { >>> - xennet_tx_buf_gc(dev); >>> - /* Under tx_lock: protects access to rx shared-ring indexes. */ >>> - if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx)) >>> - napi_schedule(&np->napi); >>> - } >>> - >>> - spin_unlock_irqrestore(&np->tx_lock, flags); >>> - >>> - return IRQ_HANDLED; >>> -} >>> - >>> static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info) >>> { >>> struct xen_netif_tx_sring *txs; >>> -- >>> 1.7.3 >