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Commit 54ef6df3 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Al Viro
Browse files

rcu: Provide counterpart to rcu_dereference() for non-RCU situations 



Although rcu_dereference() and friends can be used in situations where
object lifetimes are being managed by something other than RCU, the
resulting sparse and lockdep-RCU noise can be annoying.  This commit
therefore supplies a lockless_dereference(), which provides the
protection for dereferences without the RCU-related debugging noise.

Reported-by: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 5fecf3a1

include/linux/rcupdate.h

+15 −0
Original line number Diff line number Diff line
@@ -616,6 +616,21 @@ static inline void rcu_preempt_sleep_check(void) 
 */

#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)



/**

 * lockless_dereference() - safely load a pointer for later dereference

 * @p: The pointer to load

 *

 * Similar to rcu_dereference(), but for situations where the pointed-to

 * object's lifetime is managed by something other than RCU.  That

 * "something other" might be reference counting or simple immortality.

 */

#define lockless_dereference(p) \

({ \

	typeof(p) _________p1 = ACCESS_ONCE(p); \

	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \

	(_________p1); \

})



/**

 * rcu_assign_pointer() - assign to RCU-protected pointer

 * @p: pointer to assign to