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Subject[PATCH] (5/8) Eliminate brlock from netfilter
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Date
Replace brlock in netfilter code with RCU.

diff -urN -X dontdiff linux-2.5.64/net/core/netfilter.c linux-2.5-nobrlock/net/core/netfilter.c
--- linux-2.5.64/net/core/netfilter.c 2003-03-11 09:08:01.000000000 -0800
+++ linux-2.5-nobrlock/net/core/netfilter.c 2003-03-11 14:39:38.000000000 -0800
@@ -19,7 +19,6 @@
#include <linux/interrupt.h>
#include <linux/if.h>
#include <linux/netdevice.h>
-#include <linux/brlock.h>
#include <linux/inetdevice.h>
#include <net/sock.h>
#include <net/route.h>
@@ -46,6 +45,7 @@

struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS];
static LIST_HEAD(nf_sockopts);
+static spinlock_t nf_lock = SPIN_LOCK_UNLOCKED;

/*
* A queue handler may be registered for each protocol. Each is protected by
@@ -56,28 +56,31 @@
nf_queue_outfn_t outfn;
void *data;
} queue_handler[NPROTO];
+static spinlock_t queue_lock = SPIN_LOCK_UNLOCKED;

int nf_register_hook(struct nf_hook_ops *reg)
{
struct list_head *i;

- br_write_lock_bh(BR_NETPROTO_LOCK);
+ spin_lock_bh(&nf_lock);
for (i = nf_hooks[reg->pf][reg->hooknum].next;
i != &nf_hooks[reg->pf][reg->hooknum];
i = i->next) {
if (reg->priority < ((struct nf_hook_ops *)i)->priority)
break;
}
- list_add(&reg->list, i->prev);
- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ list_add_rcu(&reg->list, i->prev);
+ spin_unlock_bh(&nf_lock);
return 0;
}

void nf_unregister_hook(struct nf_hook_ops *reg)
{
- br_write_lock_bh(BR_NETPROTO_LOCK);
+ spin_lock_bh(&nf_lock);
list_del(&reg->list);
- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ spin_unlock_bh(&nf_lock);
+
+ synchronize_kernel();
}

/* Do exclusive ranges overlap? */
@@ -344,7 +347,9 @@
int (*okfn)(struct sk_buff *),
int hook_thresh)
{
- for (*i = (*i)->next; *i != head; *i = (*i)->next) {
+
+ for (*i = (*i)->next; *i != head; *i = (*i)->next,
+ ({ read_barrier_depends(); 0;})) {
struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;

if (hook_thresh > elem->priority)
@@ -381,15 +386,16 @@
{
int ret;

- br_write_lock_bh(BR_NETPROTO_LOCK);
+ spin_lock_bh(&queue_lock);
if (queue_handler[pf].outfn)
ret = -EBUSY;
else {
- queue_handler[pf].outfn = outfn;
queue_handler[pf].data = data;
+ wmb();
+ queue_handler[pf].outfn = outfn;
ret = 0;
}
- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ spin_unlock_bh(&queue_lock);

return ret;
}
@@ -397,10 +403,14 @@
/* The caller must flush their queue before this */
int nf_unregister_queue_handler(int pf)
{
- br_write_lock_bh(BR_NETPROTO_LOCK);
+ spin_lock_bh(&queue_lock);
queue_handler[pf].outfn = NULL;
+ wmb();
queue_handler[pf].data = NULL;
- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ spin_unlock_bh(&queue_lock);
+
+ synchronize_kernel();
+
return 0;
}

@@ -422,9 +432,10 @@
struct net_device *physoutdev = NULL;
#endif

+ rcu_read_lock();
if (!queue_handler[pf].outfn) {
kfree_skb(skb);
- return;
+ goto out;
}

info = kmalloc(sizeof(*info), GFP_ATOMIC);
@@ -433,7 +444,7 @@
printk(KERN_ERR "OOM queueing packet %p\n",
skb);
kfree_skb(skb);
- return;
+ goto out;
}

*info = (struct nf_info) {
@@ -463,8 +474,9 @@
#endif
kfree(info);
kfree_skb(skb);
- return;
}
+ out:
+ rcu_read_unlock();
}

int nf_hook_slow(int pf, unsigned int hook, struct sk_buff *skb,
@@ -491,7 +503,7 @@
}

/* We may already have this, but read-locks nest anyway */
- br_read_lock_bh(BR_NETPROTO_LOCK);
+ rcu_read_lock();

#ifdef CONFIG_NETFILTER_DEBUG
if (skb->nf_debug & (1 << hook)) {
@@ -520,7 +532,7 @@
break;
}

- br_read_unlock_bh(BR_NETPROTO_LOCK);
+ rcu_read_unlock();
return ret;
}

@@ -530,8 +542,7 @@
struct list_head *elem = &info->elem->list;
struct list_head *i;

- /* We don't have BR_NETPROTO_LOCK here */
- br_read_lock_bh(BR_NETPROTO_LOCK);
+ rcu_read_lock();
for (i = nf_hooks[info->pf][info->hook].next; i != elem; i = i->next) {
if (i == &nf_hooks[info->pf][info->hook]) {
/* The module which sent it to userspace is gone. */
@@ -569,7 +580,7 @@
kfree_skb(skb);
break;
}
- br_read_unlock_bh(BR_NETPROTO_LOCK);
+ rcu_read_unlock();

/* Release those devices we held, or Alexey will kill me. */
if (info->indev) dev_put(info->indev);


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