rcu: Provide counterpart to rcu_dereference() for non-RCU situations (54ef6df3) · Commits · 戴 / test

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:

Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

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

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