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gre: Simplify gre protocol registration locking. 

Use cmpxchg() for atomic protocol registration which saves
code and data space.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pravin B Shelar 2013-06-17 17:49:32 -07:00 committed by David S. Miller
parent ac8025a643
commit 20fd4d1f04
1 changed files with 13 additions and 27 deletions
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40
net/ipv4/gre.c
View File

@ -26,46 +26,32 @@
static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
static DEFINE_SPINLOCK(gre_proto_lock);
int gre_add_protocol(const struct gre_protocol *proto, u8 version)
{
if (version >= GREPROTO_MAX)
goto err_out;
return -EINVAL;
spin_lock(&gre_proto_lock);
if (gre_proto[version])
goto err_out_unlock;
RCU_INIT_POINTER(gre_proto[version], proto);
spin_unlock(&gre_proto_lock);
return 0;
err_out_unlock:
spin_unlock(&gre_proto_lock);
err_out:
return -1;
return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
0 : -EBUSY;
}
EXPORT_SYMBOL_GPL(gre_add_protocol);
int gre_del_protocol(const struct gre_protocol *proto, u8 version)
{
if (version >= GREPROTO_MAX)
goto err_out;
int ret;
if (version >= GREPROTO_MAX)
return -EINVAL;
ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
0 : -EBUSY;
if (ret)
return ret;
spin_lock(&gre_proto_lock);
if (rcu_dereference_protected(gre_proto[version],
lockdep_is_held(&gre_proto_lock)) != proto)
goto err_out_unlock;
RCU_INIT_POINTER(gre_proto[version], NULL);
spin_unlock(&gre_proto_lock);
synchronize_rcu();
return 0;
err_out_unlock:
spin_unlock(&gre_proto_lock);
err_out:
return -1;
}
EXPORT_SYMBOL_GPL(gre_del_protocol);