Re: [PATCH] add netconsole support for xen-netfront
From: Konrad Rzeszutek Wilk <hidden>
Date: 2012-01-23 18:27:13
Also in:
lkml, xen-devel
Subsystem:
networking drivers, the rest, xen hypervisor interface · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Juergen Gross, Stefano Stabellini
On Wed, Jan 18, 2012 at 01:06:47PM -0800, Tina Yang wrote:
On 1/18/2012 12:59 AM, Ian Campbell wrote:quoted
On Tue, 2012-01-17 at 23:15 +0000, Tina Yang wrote:quoted
On 1/17/2012 1:51 PM, Konrad Rzeszutek Wilk wrote:quoted
On Tue, Jan 17, 2012 at 01:42:22PM -0800, Tina Yang wrote:quoted
On 1/13/2012 3:06 AM, Ian Campbell wrote: 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 RDSDid you find the culprit of it? Was there a patch for that in the upstream kernel?Yes. It has nothing to do with net drivers but same cause elsewhere in the kernel.I didn't think start_xmit could be called with interrupts disabled or from interrupt context but perhaps I am wrong about that or perhaps netconsole changes things?Netdump does call it with interrupt disabled and hang because of it in 2.6.9 as I remember it. And you are right, netconsole has undergone changes from time to time, which also can change this specification.quoted
Right, Documentation/networking/netdevices.txt states that start_xmit can be called with interrupts disabled by netconsole and therefore using the irqsave/restore locking in this function is, AFAICT, correct.
Ok, so let me update the git commit description to include this. I am listed as the maintainer but I would have thought that it should go through David? David, should it go through you or should I stick it in my tree? Here is the patch with a better git description.
From 1c265b7946f222ab6a5aac5245a0ab84618772c8 Mon Sep 17 00:00:00 2001
From: Zhenzhong Duan <redacted> Date: Thu, 12 Jan 2012 10:18:29 +0800 Subject: [PATCH] xen/netfront: add netconsole support. add polling interface to xen-netfront device to support netconsole This patch also alters the spin_lock usage to use irqsave variant. Documentation/networking/netdevices.txt states that start_xmit can be called with interrupts disabled by netconsole and therefore using the irqsave/restore locking in this function is looks correct. Signed-off-by: Tina.Yang <redacted> Cc: Jeremy Fitzhardinge <redacted> Signed-off-by: Zhenzhong.Duan <redacted> Tested-by: gurudas.pai <redacted> [v1: Copy-n-pasted Ian Campbell comments] Signed-off-by: Konrad Rzeszutek Wilk <redacted> --- 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 d29365a..5a4b5df 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c@@ -478,6 +478,7 @@ 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)) {
@@ -487,12 +488,12 @@ 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; }
@@ -561,7 +562,7 @@ 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;
@@ -1176,6 +1177,33 @@ static int xennet_set_features(struct net_device *dev, u32 features) 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,
@@ -1186,6 +1214,9 @@ 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)
@@ -1388,26 +1419,6 @@ 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;
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1.7.7.5