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Commit 29fa060e authored by David S. Miller's avatar David S. Miller
Browse files

net: relax rtnl_dereference() 



rtnl_dereference() is used in contexts where RTNL is held, to fetch an
RCU protected pointer.

Updates to this pointer are prevented by RTNL, so we dont need
smp_read_barrier_depends() and the ACCESS_ONCE() provided in
rcu_dereference_check().

rtnl_dereference() is mainly a macro to document the locking invariant.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 13f5bf18

include/linux/rtnetlink.h

+6 −4
Original line number Diff line number Diff line
@@ -755,20 +755,22 @@ extern int lockdep_rtnl_is_held(void); 
 * @p: The pointer to read, prior to dereferencing

 *

 * Do an rcu_dereference(p), but check caller either holds rcu_read_lock()

 * or RTNL

 * or RTNL. Note : Please prefer rtnl_dereference() or rcu_dereference()

 */

#define rcu_dereference_rtnl(p)					\

	rcu_dereference_check(p, rcu_read_lock_held() ||	\

				 lockdep_rtnl_is_held())



/**

 * rtnl_dereference - rcu_dereference with debug checking

 * rtnl_dereference - fetch RCU pointer when updates are prevented by RTNL

 * @p: The pointer to read, prior to dereferencing

 *

 * Do an rcu_dereference(p), but check caller holds RTNL

 * Return the value of the specified RCU-protected pointer, but omit

 * both the smp_read_barrier_depends() and the ACCESS_ONCE(), because

 * caller holds RTNL.

 */

#define rtnl_dereference(p)					\

	rcu_dereference_check(p, lockdep_rtnl_is_held())

	rcu_dereference_protected(p, lockdep_rtnl_is_held())



static inline struct netdev_queue *dev_ingress_queue(struct net_device *dev)

{