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Subject[PATCH] (1/8) Eliminate brlock in psnap
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The following replaces brlock with RCU in the SNAP module.

diff -urN -X dontdiff linux-2.5.64/net/802/psnap.c linux-2.5-nobrlock/net/802/psnap.c
--- linux-2.5.64/net/802/psnap.c 2003-03-11 09:08:01.000000000 -0800
+++ linux-2.5-nobrlock/net/802/psnap.c 2003-03-10 15:48:53.000000000 -0800
@@ -21,10 +21,10 @@
#include <linux/mm.h>
#include <linux/in.h>
#include <linux/init.h>
-#include <linux/brlock.h>

LIST_HEAD(snap_list);
static struct llc_sap *snap_sap;
+static spinlock_t snap_lock = SPIN_LOCK_UNLOCKED;

/*
* Find a snap client by matching the 5 bytes.
@@ -34,17 +34,15 @@
struct list_head *entry;
struct datalink_proto *proto = NULL, *p;

- if (list_empty(&snap_list))
- goto out;
-
- list_for_each(entry, &snap_list) {
+ rcu_read_lock();
+ list_for_each_rcu(entry, &snap_list) {
p = list_entry(entry, struct datalink_proto, node);
if (!memcmp(p->type, desc, 5)) {
proto = p;
break;
}
}
-out:
+ rcu_read_unlock();
return proto;
}

@@ -124,8 +122,7 @@
{
struct datalink_proto *proto = NULL;

- br_write_lock_bh(BR_NETPROTO_LOCK);
-
+ spin_lock_bh(&snap_lock);
if (find_snap_client(desc))
goto out;

@@ -135,10 +132,10 @@
proto->rcvfunc = rcvfunc;
proto->header_length = 5 + 3; /* snap + 802.2 */
proto->request = snap_request;
- list_add(&proto->node, &snap_list);
+ list_add_rcu(&proto->node, &snap_list);
}
out:
- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ spin_unlock_bh(&snap_lock);
return proto;
}

@@ -147,12 +144,13 @@
*/
void unregister_snap_client(struct datalink_proto *proto)
{
- br_write_lock_bh(BR_NETPROTO_LOCK);
+ static RCU_HEAD(snap_rcu);

- list_del(&proto->node);
- kfree(proto);
+ spin_lock_bh(&snap_lock);
+ list_del_rcu(&proto->node);
+ spin_unlock_bh(&snap_lock);

- br_write_unlock_bh(BR_NETPROTO_LOCK);
+ call_rcu(&snap_rcu, (void (*)(void *)) kfree, proto);
}

MODULE_LICENSE("GPL");


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