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Commit 3a37f727 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: No ordering for rcu_assign_pointer() of NULL 



This commit does a compile-time check for rcu_assign_pointer() of NULL,
and uses WRITE_ONCE() rather than smp_store_release() in that case.

Reported-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 810ce8b5

include/linux/rcupdate.h

+10 −1
Original line number Original line Diff line number Diff line
@@ -650,7 +650,16 @@ static inline void rcu_preempt_sleep_check(void) 
 * please be careful when making changes to rcu_assign_pointer() and the

 * please be careful when making changes to rcu_assign_pointer() and the

 * other macros that it invokes.

 * other macros that it invokes.

 */

 */

#define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v))

#define rcu_assign_pointer(p, v)					      \

({									      \

	uintptr_t _r_a_p__v = (uintptr_t)(v);				      \

									      \

	if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL)	      \

		WRITE_ONCE((p), (typeof(p))(_r_a_p__v));		      \

	else								      \

		smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \

	_r_a_p__v;							      \

})





/**

/**

 * rcu_access_pointer() - fetch RCU pointer with no dereferencing

 * rcu_access_pointer() - fetch RCU pointer with no dereferencing