[PATCH 0/7] netpoll: recursion fixes, queueing, and cleanups

[PATCH 0/7] netpoll: recursion fixes, queueing, and cleanups

[Matt Mackall]

This patch series against 2.6.11 fixes up some recursion deadlocks in
netpoll and adds support for fallback to queueing. Various cleanups
along the way.

Holds up under load testing via ipt_LOG on a dual Opteron with tg3.
Please apply.

[PATCH 1/7] netpoll: shorten carrier detect timeout

[Matt Mackall]

Shorten carrier detect timeout to 4 seconds.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: np/net/core/netpoll.c
===================================================================
--- np.orig/net/core/netpoll.c	2005-03-03 14:13:38.700080023 -0600
+++ np/net/core/netpoll.c	2005-03-03 14:16:21.980600535 -0600
@@ -593,7 +593,7 @@ int netpoll_setup(struct netpoll *np)
 		rtnl_shunlock();
 
 		atleast = jiffies + HZ/10;
- 		atmost = jiffies + 10*HZ;
+ 		atmost = jiffies + 4*HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
 				printk(KERN_NOTICE
@@ -606,7 +606,7 @@ int netpoll_setup(struct netpoll *np)
 
 		if (time_before(jiffies, atleast)) {
 			printk(KERN_NOTICE "%s: carrier detect appears flaky,"
-			       " waiting 10 seconds\n",
+			       " waiting 4 seconds\n",
 			       np->name);
 			while (time_before(jiffies, atmost))
 				cond_resched();

[PATCH 2/7] netpoll: filter inlines

[Matt Mackall]

Add netpoll rx helpers 
Move skb_free for rx into __netpoll_rx

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rc4bk2/net/core/netpoll.c
===================================================================
--- rc4bk2.orig/net/core/netpoll.c	2005-02-14 10:34:12.000000000 -0800
+++ rc4bk2/net/core/netpoll.c	2005-02-14 17:10:34.000000000 -0800
@@ -368,7 +368,7 @@
 	netpoll_send_skb(np, send_skb);
 }
 
-int netpoll_rx(struct sk_buff *skb)
+int __netpoll_rx(struct sk_buff *skb)
 {
 	int proto, len, ulen;
 	struct iphdr *iph;
@@ -440,12 +440,18 @@
 				    (char *)(uh+1),
 				    ulen - sizeof(struct udphdr));
 
+		kfree_skb(skb);
 		return 1;
 	}
 	spin_unlock_irqrestore(&rx_list_lock, flags);
 
 out:
-	return atomic_read(&trapped);
+	if (atomic_read(&trapped)) {
+		kfree_skb(skb);
+		return 1;
+	}
+
+	return 0;
 }
 
 int netpoll_parse_options(struct netpoll *np, char *opt)
Index: rc4bk2/include/linux/netpoll.h
===================================================================
--- rc4bk2.orig/include/linux/netpoll.h	2005-02-14 10:34:08.000000000 -0800
+++ rc4bk2/include/linux/netpoll.h	2005-02-14 17:10:34.000000000 -0800
@@ -30,7 +30,15 @@
 int netpoll_trap(void);
 void netpoll_set_trap(int trap);
 void netpoll_cleanup(struct netpoll *np);
-int netpoll_rx(struct sk_buff *skb);
+int __netpoll_rx(struct sk_buff *skb);
 
+#ifdef CONFIG_NETPOLL
+static inline int netpoll_rx(struct sk_buff *skb)
+{
+	return skb->dev->netpoll_rx && __netpoll_rx(skb);
+}
+#else
+#define netpoll_rx(a) 0
+#endif
 
 #endif
Index: rc4bk2/net/core/dev.c
===================================================================
--- rc4bk2.orig/net/core/dev.c	2005-02-14 10:34:12.000000000 -0800
+++ rc4bk2/net/core/dev.c	2005-02-14 17:10:34.000000000 -0800
@@ -1427,13 +1427,10 @@
 	struct softnet_data *queue;
 	unsigned long flags;
 
-#ifdef CONFIG_NETPOLL
-	if (skb->dev->netpoll_rx && netpoll_rx(skb)) {
-		kfree_skb(skb);
+	/* if netpoll wants it, pretend we never saw it */
+	if (netpoll_rx(skb))
 		return NET_RX_DROP;
-	}
-#endif
-	
+
 	if (!skb->stamp.tv_sec)
 		net_timestamp(&skb->stamp);
 
@@ -1629,12 +1626,9 @@
 	int ret = NET_RX_DROP;
 	unsigned short type;
 
-#ifdef CONFIG_NETPOLL
-	if (skb->dev->netpoll_rx && skb->dev->poll && netpoll_rx(skb)) {
-		kfree_skb(skb);
+	/* if we've gotten here through NAPI, check netpoll */
+	if (skb->dev->poll && netpoll_rx(skb))
 		return NET_RX_DROP;
-	}
-#endif
 
 	if (!skb->stamp.tv_sec)
 		net_timestamp(&skb->stamp);

[PATCH 3/7] netpoll: add netpoll point to net_device

[Matt Mackall]

Add struct netpoll pointer to struct netdevice
Move netpoll rx flags to netpoll struct
Stop traversing rx_list and get np pointer from skb->dev->np
Remove now unneeded rx_list

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rc4/include/linux/netdevice.h
===================================================================
--- rc4.orig/include/linux/netdevice.h	2005-02-17 22:32:12.000000000 -0600
+++ rc4/include/linux/netdevice.h	2005-02-17 22:32:20.000000000 -0600
@@ -41,7 +41,7 @@
 struct divert_blk;
 struct vlan_group;
 struct ethtool_ops;
-
+struct netpoll;
 					/* source back-compat hooks */
 #define SET_ETHTOOL_OPS(netdev,ops) \
 	( (netdev)->ethtool_ops = (ops) )
@@ -471,7 +471,7 @@
 	int			(*neigh_setup)(struct net_device *dev, struct neigh_parms *);
 	int			(*accept_fastpath)(struct net_device *, struct dst_entry*);
 #ifdef CONFIG_NETPOLL
-	int			netpoll_rx;
+	struct netpoll		*np;
 #endif
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	void                    (*poll_controller)(struct net_device *dev);
Index: rc4/net/core/netpoll.c
===================================================================
--- rc4.orig/net/core/netpoll.c	2005-02-17 22:32:19.000000000 -0600
+++ rc4/net/core/netpoll.c	2005-02-17 22:39:59.000000000 -0600
@@ -35,9 +35,6 @@
 static int nr_skbs;
 static struct sk_buff *skbs;
 
-static DEFINE_SPINLOCK(rx_list_lock);
-static LIST_HEAD(rx_list);
-
 static atomic_t trapped;
 static DEFINE_SPINLOCK(netpoll_poll_lock);
 
@@ -84,13 +81,13 @@
 	queue = &__get_cpu_var(softnet_data);
 	if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&
 	    !list_empty(&queue->poll_list)) {
-		np->dev->netpoll_rx |= NETPOLL_RX_DROP;
+		np->rx_flags |= NETPOLL_RX_DROP;
 		atomic_inc(&trapped);
 
 		np->dev->poll(np->dev, &budget);
 
 		atomic_dec(&trapped);
-		np->dev->netpoll_rx &= ~NETPOLL_RX_DROP;
+		np->rx_flags &= ~NETPOLL_RX_DROP;
 	}
 	spin_unlock_irqrestore(&netpoll_poll_lock, flags);
 }
@@ -279,18 +276,7 @@
 	int size, type = ARPOP_REPLY, ptype = ETH_P_ARP;
 	u32 sip, tip;
 	struct sk_buff *send_skb;
-	unsigned long flags;
-	struct list_head *p;
-	struct netpoll *np = NULL;
-
-	spin_lock_irqsave(&rx_list_lock, flags);
-	list_for_each(p, &rx_list) {
-		np = list_entry(p, struct netpoll, rx_list);
-		if ( np->dev == skb->dev )
-			break;
-		np = NULL;
-	}
-	spin_unlock_irqrestore(&rx_list_lock, flags);
+	struct netpoll *np = skb->dev->np;
 
 	if (!np) return;
 
@@ -373,10 +359,10 @@
 	int proto, len, ulen;
 	struct iphdr *iph;
 	struct udphdr *uh;
-	struct netpoll *np;
-	struct list_head *p;
-	unsigned long flags;
+	struct netpoll *np = skb->dev->np;
 
+	if (!np->rx_hook)
+		goto out;
 	if (skb->dev->type != ARPHRD_ETHER)
 		goto out;
 
@@ -420,30 +406,19 @@
 		goto out;
 	if (checksum_udp(skb, uh, ulen, iph->saddr, iph->daddr) < 0)
 		goto out;
+	if (np->local_ip && np->local_ip != ntohl(iph->daddr))
+		goto out;
+	if (np->remote_ip && np->remote_ip != ntohl(iph->saddr))
+		goto out;
+	if (np->local_port && np->local_port != ntohs(uh->dest))
+		goto out;
 
-	spin_lock_irqsave(&rx_list_lock, flags);
-	list_for_each(p, &rx_list) {
-		np = list_entry(p, struct netpoll, rx_list);
-		if (np->dev && np->dev != skb->dev)
-			continue;
-		if (np->local_ip && np->local_ip != ntohl(iph->daddr))
-			continue;
-		if (np->remote_ip && np->remote_ip != ntohl(iph->saddr))
-			continue;
-		if (np->local_port && np->local_port != ntohs(uh->dest))
-			continue;
-
-		spin_unlock_irqrestore(&rx_list_lock, flags);
-
-		if (np->rx_hook)
-			np->rx_hook(np, ntohs(uh->source),
-				    (char *)(uh+1),
-				    ulen - sizeof(struct udphdr));
+	np->rx_hook(np, ntohs(uh->source),
+		    (char *)(uh+1),
+		    ulen - sizeof(struct udphdr));
 
-		kfree_skb(skb);
-		return 1;
-	}
-	spin_unlock_irqrestore(&rx_list_lock, flags);
+	kfree_skb(skb);
+	return 1;
 
 out:
 	if (atomic_read(&trapped)) {
@@ -574,6 +549,10 @@
 		       np->name, np->dev_name);
 		return -1;
 	}
+
+	np->dev = ndev;
+	ndev->np = np;
+
 	if (!ndev->poll_controller) {
 		printk(KERN_ERR "%s: %s doesn't support polling, aborting.\n",
 		       np->name, np->dev_name);
@@ -639,36 +618,22 @@
 		       np->name, HIPQUAD(np->local_ip));
 	}
 
-	np->dev = ndev;
-
-	if(np->rx_hook) {
-		unsigned long flags;
-
-		np->dev->netpoll_rx = NETPOLL_RX_ENABLED;
-
-		spin_lock_irqsave(&rx_list_lock, flags);
-		list_add(&np->rx_list, &rx_list);
-		spin_unlock_irqrestore(&rx_list_lock, flags);
-	}
+	if(np->rx_hook)
+		np->rx_flags = NETPOLL_RX_ENABLED;
 
 	return 0;
+
  release:
+	ndev->np = NULL;
+	np->dev = NULL;
 	dev_put(ndev);
 	return -1;
 }
 
 void netpoll_cleanup(struct netpoll *np)
 {
-	if (np->rx_hook) {
-		unsigned long flags;
-
-		spin_lock_irqsave(&rx_list_lock, flags);
-		list_del(&np->rx_list);
-		spin_unlock_irqrestore(&rx_list_lock, flags);
-	}
-
 	if (np->dev)
-		np->dev->netpoll_rx = 0;
+		np->dev->np = NULL;
 	dev_put(np->dev);
 	np->dev = NULL;
 }
Index: rc4/include/linux/netpoll.h
===================================================================
--- rc4.orig/include/linux/netpoll.h	2005-02-17 22:32:19.000000000 -0600
+++ rc4/include/linux/netpoll.h	2005-02-17 22:39:59.000000000 -0600
@@ -16,11 +16,11 @@
 struct netpoll {
 	struct net_device *dev;
 	char dev_name[16], *name;
+	int rx_flags;
 	void (*rx_hook)(struct netpoll *, int, char *, int);
 	u32 local_ip, remote_ip;
 	u16 local_port, remote_port;
 	unsigned char local_mac[6], remote_mac[6];
-	struct list_head rx_list;
 };
 
 void netpoll_poll(struct netpoll *np);
@@ -35,7 +35,7 @@
 #ifdef CONFIG_NETPOLL
 static inline int netpoll_rx(struct sk_buff *skb)
 {
-	return skb->dev->netpoll_rx && __netpoll_rx(skb);
+	return skb->dev->np && skb->dev->np->rx_flags && __netpoll_rx(skb);
 }
 #else
 #define netpoll_rx(a) 0

[PATCH 4/7] netpoll: fix ->poll() locking

[Matt Mackall]

Introduce a per-client poll lock and flag. The lock assures we never
have more than one caller in dev->poll(). The flag provides recursion
avoidance on UP where the lock disappears.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rc4/net/core/netpoll.c
===================================================================
--- rc4.orig/net/core/netpoll.c	2005-02-17 22:39:59.000000000 -0600
+++ rc4/net/core/netpoll.c	2005-02-17 22:40:02.000000000 -0600
@@ -36,7 +36,6 @@
 static struct sk_buff *skbs;
 
 static atomic_t trapped;
-static DEFINE_SPINLOCK(netpoll_poll_lock);
 
 #define NETPOLL_RX_ENABLED  1
 #define NETPOLL_RX_DROP     2
@@ -63,8 +62,15 @@
 }
 
 /*
- * Check whether delayed processing was scheduled for our current CPU,
- * and then manually invoke NAPI polling to pump data off the card.
+ * Check whether delayed processing was scheduled for our NIC. If so,
+ * we attempt to grab the poll lock and use ->poll() to pump the card.
+ * If this fails, either we've recursed in ->poll() or it's already
+ * running on another CPU.
+ *
+ * Note: we don't mask interrupts with this lock because we're using
+ * trylock here and interrupts are already disabled in the softirq
+ * case. Further, we test the poll_owner to avoid recursion on UP
+ * systems where the lock doesn't exist.
  *
  * In cases where there is bi-directional communications, reading only
  * one message at a time can lead to packets being dropped by the
@@ -74,13 +80,10 @@
 static void poll_napi(struct netpoll *np)
 {
 	int budget = 16;
-	unsigned long flags;
-	struct softnet_data *queue;
 
-	spin_lock_irqsave(&netpoll_poll_lock, flags);
-	queue = &__get_cpu_var(softnet_data);
 	if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&
-	    !list_empty(&queue->poll_list)) {
+	    np->poll_owner != __smp_processor_id() &&
+	    spin_trylock(&np->poll_lock)) {
 		np->rx_flags |= NETPOLL_RX_DROP;
 		atomic_inc(&trapped);
 
@@ -88,8 +91,8 @@
 
 		atomic_dec(&trapped);
 		np->rx_flags &= ~NETPOLL_RX_DROP;
+		spin_unlock(&np->poll_lock);
 	}
-	spin_unlock_irqrestore(&netpoll_poll_lock, flags);
 }
 
 void netpoll_poll(struct netpoll *np)
@@ -194,6 +197,12 @@
 		return;
 	}
 
+	/* avoid ->poll recursion */
+	if(np->poll_owner == __smp_processor_id()) {
+		__kfree_skb(skb);
+		return;
+	}
+
 	spin_lock(&np->dev->xmit_lock);
 	np->dev->xmit_lock_owner = smp_processor_id();
 
@@ -542,6 +551,9 @@
 	struct net_device *ndev = NULL;
 	struct in_device *in_dev;
 
+	np->poll_lock = SPIN_LOCK_UNLOCKED;
+	np->poll_owner = -1;
+
 	if (np->dev_name)
 		ndev = dev_get_by_name(np->dev_name);
 	if (!ndev) {
Index: rc4/include/linux/netpoll.h
===================================================================
--- rc4.orig/include/linux/netpoll.h	2005-02-17 22:39:59.000000000 -0600
+++ rc4/include/linux/netpoll.h	2005-02-17 22:40:02.000000000 -0600
@@ -21,6 +21,8 @@
 	u32 local_ip, remote_ip;
 	u16 local_port, remote_port;
 	unsigned char local_mac[6], remote_mac[6];
+	spinlock_t poll_lock;
+	int poll_owner;
 };
 
 void netpoll_poll(struct netpoll *np);
@@ -37,8 +39,27 @@
 {
 	return skb->dev->np && skb->dev->np->rx_flags && __netpoll_rx(skb);
 }
+
+static inline void netpoll_poll_lock(struct net_device *dev)
+{
+	if (dev->np) {
+		spin_lock(&dev->np->poll_lock);
+		dev->np->poll_owner = __smp_processor_id();
+	}
+}
+
+static inline void netpoll_poll_unlock(struct net_device *dev)
+{
+	if (dev->np) {
+		spin_unlock(&dev->np->poll_lock);
+		dev->np->poll_owner = -1;
+	}
+}
+
 #else
 #define netpoll_rx(a) 0
+#define netpoll_poll_lock(a)
+#define netpoll_poll_unlock(a)
 #endif
 
 #endif
Index: rc4/net/core/dev.c
===================================================================
--- rc4.orig/net/core/dev.c	2005-02-17 22:39:59.000000000 -0600
+++ rc4/net/core/dev.c	2005-02-17 22:40:02.000000000 -0600
@@ -1775,8 +1775,10 @@
 
 		dev = list_entry(queue->poll_list.next,
 				 struct net_device, poll_list);
+		netpoll_poll_lock(dev);
 
 		if (dev->quota <= 0 || dev->poll(dev, &budget)) {
+			netpoll_poll_unlock(dev);
 			local_irq_disable();
 			list_del(&dev->poll_list);
 			list_add_tail(&dev->poll_list, &queue->poll_list);
@@ -1785,6 +1787,7 @@
 			else
 				dev->quota = dev->weight;
 		} else {
+			netpoll_poll_unlock(dev);
 			dev_put(dev);
 			local_irq_disable();
 		}

[PATCH 5/7] netpoll: add optional dropping and queueing support

[Matt Mackall]

This adds a callback for packets we can't deliver immediately and a
helper function for clients to queue such packets to the device
post-interrupt. 

Netconsole is modified to use the queueing function for best-effort
delivery.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rc4/drivers/net/netconsole.c
===================================================================
--- rc4.orig/drivers/net/netconsole.c	2005-02-17 22:39:29.000000000 -0600
+++ rc4/drivers/net/netconsole.c	2005-02-17 22:40:05.000000000 -0600
@@ -60,6 +60,7 @@
 	.local_port = 6665,
 	.remote_port = 6666,
 	.remote_mac = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+	.drop = netpoll_queue,
 };
 static int configured = 0;
 
Index: rc4/net/core/netpoll.c
===================================================================
--- rc4.orig/net/core/netpoll.c	2005-02-17 22:40:02.000000000 -0600
+++ rc4/net/core/netpoll.c	2005-02-17 22:40:05.000000000 -0600
@@ -19,6 +19,7 @@
 #include <linux/netpoll.h>
 #include <linux/sched.h>
 #include <linux/rcupdate.h>
+#include <linux/workqueue.h>
 #include <net/tcp.h>
 #include <net/udp.h>
 #include <asm/unaligned.h>
@@ -28,13 +29,18 @@
  * message gets out even in extreme OOM situations.
  */
 
-#define MAX_SKBS 32
 #define MAX_UDP_CHUNK 1460
+#define MAX_SKBS 32
+#define MAX_QUEUE_DEPTH (MAX_SKBS / 2)
 
 static DEFINE_SPINLOCK(skb_list_lock);
 static int nr_skbs;
 static struct sk_buff *skbs;
 
+static DEFINE_SPINLOCK(queue_lock);
+static int queue_depth;
+static struct sk_buff *queue_head, *queue_tail;
+
 static atomic_t trapped;
 
 #define NETPOLL_RX_ENABLED  1
@@ -46,6 +52,50 @@
 
 static void zap_completion_queue(void);
 
+static void queue_process(void *p)
+{
+	unsigned long flags;
+	struct sk_buff *skb;
+
+	while (queue_head) {
+		spin_lock_irqsave(&queue_lock, flags);
+
+		skb = queue_head;
+		queue_head = skb->next;
+		if (skb == queue_tail)
+			queue_head = NULL;
+
+		queue_depth--;
+
+		spin_unlock_irqrestore(&queue_lock, flags);
+
+		dev_queue_xmit(skb);
+	}
+}
+
+static DECLARE_WORK(send_queue, queue_process, NULL);
+
+void netpoll_queue(struct sk_buff *skb)
+{
+	unsigned long flags;
+
+	if (queue_depth == MAX_QUEUE_DEPTH) {
+		__kfree_skb(skb);
+		return;
+	}
+
+	spin_lock_irqsave(&queue_lock, flags);
+	if (!queue_head)
+		queue_head = skb;
+	else
+		queue_tail->next = skb;
+	queue_tail = skb;
+	queue_depth++;
+	spin_unlock_irqrestore(&queue_lock, flags);
+
+	schedule_work(&send_queue);
+}
+
 static int checksum_udp(struct sk_buff *skb, struct udphdr *uh,
 			     unsigned short ulen, u32 saddr, u32 daddr)
 {
@@ -199,7 +249,10 @@
 
 	/* avoid ->poll recursion */
 	if(np->poll_owner == __smp_processor_id()) {
-		__kfree_skb(skb);
+		if (np->drop)
+			np->drop(skb);
+		else
+			__kfree_skb(skb);
 		return;
 	}
 
@@ -275,6 +328,8 @@
 	memcpy(eth->h_source, np->local_mac, 6);
 	memcpy(eth->h_dest, np->remote_mac, 6);
 
+	skb->dev = np->dev;
+
 	netpoll_send_skb(np, skb);
 }
 
Index: rc4/include/linux/netpoll.h
===================================================================
--- rc4.orig/include/linux/netpoll.h	2005-02-17 22:40:02.000000000 -0600
+++ rc4/include/linux/netpoll.h	2005-02-17 22:40:05.000000000 -0600
@@ -18,6 +18,7 @@
 	char dev_name[16], *name;
 	int rx_flags;
 	void (*rx_hook)(struct netpoll *, int, char *, int);
+	void (*drop)(struct sk_buff *skb);
 	u32 local_ip, remote_ip;
 	u16 local_port, remote_port;
 	unsigned char local_mac[6], remote_mac[6];
@@ -33,6 +34,7 @@
 void netpoll_set_trap(int trap);
 void netpoll_cleanup(struct netpoll *np);
 int __netpoll_rx(struct sk_buff *skb);
+void netpoll_queue(struct sk_buff *skb);
 
 #ifdef CONFIG_NETPOLL
 static inline int netpoll_rx(struct sk_buff *skb)

[PATCH 6/7] netpoll: handle xmit_lock recursion similarly

[Matt Mackall]

Handle possible recursion on xmit_lock while we're at it.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: rc4/net/core/netpoll.c
===================================================================
--- rc4.orig/net/core/netpoll.c	2005-02-17 22:40:05.000000000 -0600
+++ rc4/net/core/netpoll.c	2005-02-17 22:40:07.000000000 -0600
@@ -247,8 +247,9 @@
 		return;
 	}
 
-	/* avoid ->poll recursion */
-	if(np->poll_owner == __smp_processor_id()) {
+	/* avoid recursion */
+	if(np->poll_owner == __smp_processor_id() ||
+	   np->dev->xmit_lock_owner == __smp_processor_id()) {
 		if (np->drop)
 			np->drop(skb);
 		else

[PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[Matt Mackall]

Packets that have destructors should not be zapped here as that might
produce additional printk warnings via netconsole.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: np/net/core/netpoll.c
===================================================================
--- np.orig/net/core/netpoll.c	2005-03-03 14:16:29.579809668 -0600
+++ np/net/core/netpoll.c	2005-03-03 14:17:21.167652225 -0600
@@ -192,7 +192,8 @@ static void zap_completion_queue(void)
 		while (clist != NULL) {
 			struct sk_buff *skb = clist;
 			clist = clist->next;
-			__kfree_skb(skb);
+			if(!skb->destructor)
+				__kfree_skb(skb);
 		}
 	}
 

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[David S. Miller]

On Thu, 03 Mar 2005 14:46:32 -0600
Matt Mackall <mpm@selenic.com> wrote:

> Packets that have destructors should not be zapped here as that might
> produce additional printk warnings via netconsole.
> 
> Signed-off-by: Matt Mackall <mpm@selenic.com>

Then where will they be freed, eh? :-)

This patch adds an SKB leak.  Since you've NULL'd out the list, any
SKB skipped will never be freed up at all.

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[Jeff Garzik]

David S. Miller wrote:
> On Thu, 03 Mar 2005 14:46:32 -0600
> Matt Mackall <mpm@selenic.com> wrote:
> 
> 
>>Packets that have destructors should not be zapped here as that might
>>produce additional printk warnings via netconsole.
>>
>>Signed-off-by: Matt Mackall <mpm@selenic.com>
> 
> 
> Then where will they be freed, eh? :-)
> 
> This patch adds an SKB leak.  Since you've NULL'd out the list, any
> SKB skipped will never be freed up at all.

Heh, I was just writing this same message.

On a related note...  David, I would prefer if you merged up the netpoll 
stuff, since it touches mainly net/*

Is that cool w/ you?

	Jeff

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[David S. Miller]

On Thu, 03 Mar 2005 16:17:10 -0500
Jeff Garzik <jgarzik@pobox.com> wrote:

> Heh, I was just writing this same message.
> 
> On a related note...  David, I would prefer if you merged up the netpoll 
> stuff, since it touches mainly net/*
> 
> Is that cool w/ you?

No problem.  I still don't like this code in that it adds a locking
penalty to everyone just by virtue of enabling netpoll.  We've worked
so hard with things like NETIF_F_LLTX to eliminate locking, so this
would be a huge step backwards.

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[Jeff Garzik]

On Thu, Mar 03, 2005 at 01:29:06PM -0800, David S. Miller wrote:
> On Thu, 03 Mar 2005 16:17:10 -0500
> Jeff Garzik <jgarzik@pobox.com> wrote:
> 
> > Heh, I was just writing this same message.
> > 
> > On a related note...  David, I would prefer if you merged up the netpoll 
> > stuff, since it touches mainly net/*
> > 
> > Is that cool w/ you?
> 
> No problem.  I still don't like this code in that it adds a locking
> penalty to everyone just by virtue of enabling netpoll.  We've worked
> so hard with things like NETIF_F_LLTX to eliminate locking, so this
> would be a huge step backwards.

Agreed.

	Jeff

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[Matt Mackall]

On Thu, Mar 03, 2005 at 01:29:06PM -0800, David S. Miller wrote:
> On Thu, 03 Mar 2005 16:17:10 -0500
> Jeff Garzik <jgarzik@pobox.com> wrote:
> 
> > Heh, I was just writing this same message.
> > 
> > On a related note...  David, I would prefer if you merged up the netpoll 
> > stuff, since it touches mainly net/*
> > 
> > Is that cool w/ you?
> 
> No problem.  I still don't like this code in that it adds a locking
> penalty to everyone just by virtue of enabling netpoll.  We've worked
> so hard with things like NETIF_F_LLTX to eliminate locking, so this
> would be a huge step backwards.

The lock only happens if CONFIG_NETPOLL=y _and_ a netpoll client (eg
netconsole) is registered on the device in question.

I'm certainly open to ideas that improve upon that, but everything
I've come up with is equivalent in cost to a lock.

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[David S. Miller]

On Thu, 3 Mar 2005 13:39:11 -0800
Matt Mackall <mpm@selenic.com> wrote:

> The lock only happens if CONFIG_NETPOLL=y _and_ a netpoll client (eg
> netconsole) is registered on the device in question.

I actually missed that condition.  This is less intrusive then.
I'm actually ok with these changes therefore.

I'll merge these patches in (with the SKB leak fix of course)
and will push upstream once we work out how 2.6.x development
is going to process :-)

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[Matt Mackall]

On Thu, Mar 03, 2005 at 01:00:31PM -0800, David S. Miller wrote:
> On Thu, 03 Mar 2005 14:46:32 -0600
> Matt Mackall <mpm@selenic.com> wrote:
> 
> > Packets that have destructors should not be zapped here as that might
> > produce additional printk warnings via netconsole.
> > 
> > Signed-off-by: Matt Mackall <mpm@selenic.com>
> 
> Then where will they be freed, eh? :-)
> 
> This patch adds an SKB leak.  Since you've NULL'd out the list, any
> SKB skipped will never be freed up at all.

Doh. Plain as day. How's this look?

Packets that have destructors should not be zapped here as that might
produce additional printk warnings via netconsole.

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: np/net/core/netpoll.c
===================================================================
--- np.orig/net/core/netpoll.c	2005-03-03 14:16:29.579809668 -0600
+++ np/net/core/netpoll.c	2005-03-03 15:26:38.826754614 -0600
@@ -192,7 +192,10 @@ static void zap_completion_queue(void)
 		while (clist != NULL) {
 			struct sk_buff *skb = clist;
 			clist = clist->next;
-			__kfree_skb(skb);
+			if(skb->destructor)
+				dev_kfree_skb_any(skb); /* put this one back */
+			else
+				__kfree_skb(skb);
 		}
 	}
 


-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 7/7] netpoll: avoid kfree_skb on packets with destructo

[David S. Miller]

On Thu, 3 Mar 2005 13:32:28 -0800
Matt Mackall <mpm@selenic.com> wrote:

> Doh. Plain as day. How's this look?
> 
> Packets that have destructors should not be zapped here as that might
> produce additional printk warnings via netconsole.
> 
> Signed-off-by: Matt Mackall <mpm@selenic.com>

Looks great Matt, applied.

Thanks.

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[Jeff Moyer]

==> Regarding [PATCH 4/7] netpoll: fix ->poll() locking; Matt Mackall <mpm@selenic.com> adds:

mpm> Introduce a per-client poll lock and flag. The lock assures we never
mpm> have more than one caller in dev->poll(). The flag provides recursion
mpm> avoidance on UP where the lock disappears.

I don't think it makes sense to have the poll lock associated with a struct
netpoll.  We want to guard simultaneous access to the device's poll
routine.  With this implementation, if we have multiple netpoll clients
running at the same time, we can have multiple callers of dev->poll at the
same time.  In other words, there is not a 1:1 relationship between struct
netpoll's and struct net_device's.

Please consider making this a per device lock.

-Jeff

@@ -74,13 +80,10 @@
 static void poll_napi(struct netpoll *np)
 {
 	int budget = 16;
-	unsigned long flags;
-	struct softnet_data *queue;
 
-	spin_lock_irqsave(&netpoll_poll_lock, flags);
-	queue = &__get_cpu_var(softnet_data);
 	if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&
-	    !list_empty(&queue->poll_list)) {
+	    np->poll_owner != __smp_processor_id() &&
+	    spin_trylock(&np->poll_lock)) {
 		np->rx_flags |= NETPOLL_RX_DROP;
 		atomic_inc(&trapped);

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[David S. Miller]

On Fri, 22 Apr 2005 18:24:46 -0400
Jeff Moyer <jmoyer@redhat.com> wrote:

> ==> Regarding [PATCH 4/7] netpoll: fix ->poll() locking; Matt Mackall <mpm@selenic.com> adds:
> 
> mpm> Introduce a per-client poll lock and flag. The lock assures we never
> mpm> have more than one caller in dev->poll(). The flag provides recursion
> mpm> avoidance on UP where the lock disappears.
> 
> I don't think it makes sense to have the poll lock associated with a struct
> netpoll.

There should be a 1 to 1 relationship from netdev to netpoll, but I see
no problems with a many to 1 relationship from netdev to netpoll, that
is perfectly legal.  It would give more stringent locking on dev->poll()
invocations, not forget to lock when necessary.

The only thing which is wrong is that netpoll_setup() should verify that
netdev->np is NULL, and if it is not it should return an error.

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[Jeff Moyer]

==> Regarding Re: [PATCH 4/7] netpoll: fix ->poll() locking; "David S. Miller" <davem@davemloft.net> adds:

davem> On Fri, 22 Apr 2005 18:24:46 -0400 Jeff Moyer <jmoyer@redhat.com>
davem> wrote:

>> ==> Regarding [PATCH 4/7] netpoll: fix ->poll() locking; Matt Mackall
>> <mpm@selenic.com> adds:
>> 
mpm> Introduce a per-client poll lock and flag. The lock assures we never
mpm> have more than one caller in dev->poll(). The flag provides recursion
mpm> avoidance on UP where the lock disappears.
>> I don't think it makes sense to have the poll lock associated with a
>> struct netpoll.

davem> There should be a 1 to 1 relationship from netdev to netpoll, but I
davem> see no problems with a many to 1 relationship from netdev to
davem> netpoll, that is perfectly legal.  It would give more stringent
davem> locking on dev->poll() invocations, not forget to lock when
davem> necessary.

davem> The only thing which is wrong is that netpoll_setup() should verify
davem> that netdev-> np is NULL, and if it is not it should return an error.

Oh yes, of course.  Somehow I managed to forget that we now squirrel away
the struct netpoll pointer in the net_device.  Previously you could
register multiple netpoll clients to one device, and this was useful for
say doing netconsole and netdump over the same interface.  If we've removed
this ability, this is a bad thing.  Oh dear...

-Jeff

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[David S. Miller]

On Fri, 22 Apr 2005 19:02:43 -0400
Jeff Moyer <jmoyer@redhat.com> wrote:

> Oh yes, of course.  Somehow I managed to forget that we now squirrel away
> the struct netpoll pointer in the net_device.  Previously you could
> register multiple netpoll clients to one device, and this was useful for
> say doing netconsole and netdump over the same interface.  If we've removed
> this ability, this is a bad thing.  Oh dear...

In such a configuration, how did the netpoll code "tell" who the
receive packets were for or did it send them to all registered
netpoll clients for that device?

Just curious.

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[Matt Mackall]

On Fri, Apr 22, 2005 at 03:59:58PM -0700, David S. Miller wrote:
> On Fri, 22 Apr 2005 19:02:43 -0400
> Jeff Moyer <jmoyer@redhat.com> wrote:
> 
> > Oh yes, of course.  Somehow I managed to forget that we now squirrel away
> > the struct netpoll pointer in the net_device.  Previously you could
> > register multiple netpoll clients to one device, and this was useful for
> > say doing netconsole and netdump over the same interface.  If we've removed
> > this ability, this is a bad thing.  Oh dear...

Hrm, it appears I forgot about that when I did the recent rework.

> In such a configuration, how did the netpoll code "tell" who the
> receive packets were for or did it send them to all registered
> netpoll clients for that device?

It walked a global list of clients.

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 4/7] netpoll: fix ->poll() locking

[David S. Miller]

On Fri, 22 Apr 2005 19:14:40 -0700
Matt Mackall <mpm@selenic.com> wrote:

> > In such a configuration, how did the netpoll code "tell" who the
> > receive packets were for or did it send them to all registered
> > netpoll clients for that device?
> 
> It walked a global list of clients.

Ok, we definitely need to fix this.

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Patrick McHardy]

[-- Attachment #1: Type: text/plain, Size: 372 bytes --]

Matt Mackall wrote:
> Shorten carrier detect timeout to 4 seconds.

The carrier detection looks partially broken to me. The current logic
detects an instantly available carrier as flaky because
netif_carrier_ok() takes less than 1/10s. This patch does what
I assume is intended, make sure the carrier is stable for 1/10s.

Signed-off-by: Patrick McHardy <kaber@trash.net>

[-- Attachment #2: x --]
[-- Type: text/plain, Size: 837 bytes --]

===== net/core/netpoll.c 1.27 vs edited =====
--- 1.27/net/core/netpoll.c	2005-01-26 06:32:56 +01:00
+++ edited/net/core/netpoll.c	2005-03-06 01:07:16 +01:00
@@ -592,8 +592,7 @@
 		}
 		rtnl_shunlock();
 
-		atleast = jiffies + HZ/10;
- 		atmost = jiffies + 10*HZ;
+ 		atmost = jiffies + 4*HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
 				printk(KERN_NOTICE
@@ -604,9 +603,15 @@
 			cond_resched();
 		}
 
+		atleast = jiffies + HZ/10;
+		while (netif_carrier_ok(ndev)) {
+			if (time_after(jiffies, atleast))
+				break;
+			cond_resched();
+		}
 		if (time_before(jiffies, atleast)) {
 			printk(KERN_NOTICE "%s: carrier detect appears flaky,"
-			       " waiting 10 seconds\n",
+			       " waiting 4 seconds\n",
 			       np->name);
 			while (time_before(jiffies, atmost))
 				cond_resched();

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Matt Mackall]

On Sun, Mar 06, 2005 at 01:09:28AM +0100, Patrick McHardy wrote:
> Matt Mackall wrote:
> >Shorten carrier detect timeout to 4 seconds.
> 
> The carrier detection looks partially broken to me. The current logic
> detects an instantly available carrier as flaky because
> netif_carrier_ok() takes less than 1/10s. This patch does what
> I assume is intended, make sure the carrier is stable for 1/10s.

Looks ok, but I've been meaning to change the second loop to something
like msleep(). 

Did you try this with a card that otherwise goes into the wait?

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Patrick McHardy]

[-- Attachment #1: Type: text/plain, Size: 747 bytes --]

Matt Mackall wrote:
> On Sun, Mar 06, 2005 at 01:09:28AM +0100, Patrick McHardy wrote:
>>
>>The carrier detection looks partially broken to me. The current logic
>>detects an instantly available carrier as flaky because
>>netif_carrier_ok() takes less than 1/10s. This patch does what
>>I assume is intended, make sure the carrier is stable for 1/10s.
> 
> 
> Looks ok, but I've been meaning to change the second loop to something
> like msleep(). 

How about this one ? I also removed oflags, reading it outside of
the locked section was racy.

> Did you try this with a card that otherwise goes into the wait?

Yes, I tried with sk98lin. I don't have a card here that actually
supports netpoll.

Signed-off-by: Patrick McHardy <kaber@trash.net>

[-- Attachment #2: x --]
[-- Type: text/plain, Size: 1605 bytes --]

===== net/core/netpoll.c 1.27 vs edited =====
--- 1.27/net/core/netpoll.c	2005-01-26 06:32:56 +01:00
+++ edited/net/core/netpoll.c	2005-03-06 01:58:48 +01:00
@@ -18,6 +18,7 @@
 #include <linux/interrupt.h>
 #include <linux/netpoll.h>
 #include <linux/sched.h>
+#include <linux/delay.h>
 #include <linux/rcupdate.h>
 #include <net/tcp.h>
 #include <net/udp.h>
@@ -575,16 +576,14 @@
 	}
 
 	if (!netif_running(ndev)) {
-		unsigned short oflags;
 		unsigned long atmost, atleast;
+		long left;
 
 		printk(KERN_INFO "%s: device %s not up yet, forcing it\n",
 		       np->name, np->dev_name);
 
-		oflags = ndev->flags;
-
 		rtnl_shlock();
-		if (dev_change_flags(ndev, oflags | IFF_UP) < 0) {
+		if (dev_change_flags(ndev, ndev->flags | IFF_UP) < 0) {
 			printk(KERN_ERR "%s: failed to open %s\n",
 			       np->name, np->dev_name);
 			rtnl_shunlock();
@@ -592,8 +591,7 @@
 		}
 		rtnl_shunlock();
 
-		atleast = jiffies + HZ/10;
- 		atmost = jiffies + 10*HZ;
+ 		atmost = jiffies + 4*HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
 				printk(KERN_NOTICE
@@ -604,12 +602,16 @@
 			cond_resched();
 		}
 
+		atleast = jiffies + HZ/10;
+		while (netif_carrier_ok(ndev) && time_before(jiffies, atleast))
+			cond_resched();
 		if (time_before(jiffies, atleast)) {
 			printk(KERN_NOTICE "%s: carrier detect appears flaky,"
-			       " waiting 10 seconds\n",
+			       " waiting 4 seconds\n",
 			       np->name);
-			while (time_before(jiffies, atmost))
-				cond_resched();
+			left = atmost - jiffies;
+			if (left > 0)
+				msleep(jiffies_to_msecs(left));
 		}
 	}
 

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Matt Mackall]

On Sun, Mar 06, 2005 at 02:01:01AM +0100, Patrick McHardy wrote:
> Matt Mackall wrote:
> >On Sun, Mar 06, 2005 at 01:09:28AM +0100, Patrick McHardy wrote:
> >>
> >>The carrier detection looks partially broken to me. The current logic
> >>detects an instantly available carrier as flaky because
> >>netif_carrier_ok() takes less than 1/10s. This patch does what
> >>I assume is intended, make sure the carrier is stable for 1/10s.

Ok, on closer inspection, the current logic is: the NIC reports
carrier detect nearly instaneously and thus its carrier detect
reporting is considered unreliable. Rather than immediately sending
packets, we wait for some interval for it to really be up so that the
backlog of console messages doesn't get pumped into the bit bucket.

So I'm going to change it from "flaky" to "untrustworthy" and add a
comment.

> How about this one ? I also removed oflags, reading it outside of
> the locked section was racy.

I'll do this as a separate patch.

> >Did you try this with a card that otherwise goes into the wait?
> 
> Yes, I tried with sk98lin. I don't have a card here that actually
> supports netpoll.

Huh? sk98lin appears to support it?

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Patrick McHardy]

Matt Mackall wrote:
> Ok, on closer inspection, the current logic is: the NIC reports
> carrier detect nearly instaneously and thus its carrier detect
> reporting is considered unreliable. Rather than immediately sending
> packets, we wait for some interval for it to really be up so that the
> backlog of console messages doesn't get pumped into the bit bucket.
> 
> So I'm going to change it from "flaky" to "untrustworthy" and add a
> comment.

Why don't you trust an instaneously available carrier? Any
reason to assume there will be false positives?

Regards
Patrick

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Matt Mackall]

On Fri, Mar 11, 2005 at 05:35:05AM +0100, Patrick McHardy wrote:
> Matt Mackall wrote:
> >Ok, on closer inspection, the current logic is: the NIC reports
> >carrier detect nearly instaneously and thus its carrier detect
> >reporting is considered unreliable. Rather than immediately sending
> >packets, we wait for some interval for it to really be up so that the
> >backlog of console messages doesn't get pumped into the bit bucket.
> >
> >So I'm going to change it from "flaky" to "untrustworthy" and add a
> >comment.
> 
> Why don't you trust an instaneously available carrier? Any
> reason to assume there will be false positives?

Because I had reports of people losing all their boot messages until
this logic was added (about a year ago now?). I don't remember which
NICs were implicated, but some apparently report carrier is always
available.

-- 
Mathematics is the supreme nostalgia of our time.

Re: [PATCH 1/7] netpoll: shorten carrier detect timeout

[Patrick McHardy]

Matt Mackall wrote:
> On Fri, Mar 11, 2005 at 05:35:05AM +0100, Patrick McHardy wrote:
> 
>>>So I'm going to change it from "flaky" to "untrustworthy" and add a
>>>comment.
>>
>>Why don't you trust an instaneously available carrier? Any
>>reason to assume there will be false positives?
> 
> 
> Because I had reports of people losing all their boot messages until
> this logic was added (about a year ago now?). I don't remember which
> NICs were implicated, but some apparently report carrier is always
> available.

If this problem is not common, I think it would be better to make
this behaviour dependant on a boot parameter instead of forcing
everyone to wait for 4s. Additionally you could have a blacklist
of flaky NICs.

Regards
Patrick