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    Subject[PATCH] (1/8) Eliminate brlock in psnap
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    Date
    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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