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Commit 26e3e3cb authored by Bart Van Assche's avatar Bart Van Assche Committed by Martin K. Petersen
Browse files

scsi: rcu: Introduce rcu_swap_protected() 



A common pattern in RCU code is to assign a new value to an RCU pointer
after having read and stored the old value. Introduce a macro for this
pattern.

Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Shane M Seymour <shane.seymour@hpe.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent fbf25233

include/linux/rcupdate.h

+16 −0
Original line number Diff line number Diff line
@@ -407,6 +407,22 @@ static inline void rcu_preempt_sleep_check(void) { } 
	_r_a_p__v;							      \

})



/**

 * rcu_swap_protected() - swap an RCU and a regular pointer

 * @rcu_ptr: RCU pointer

 * @ptr: regular pointer

 * @c: the conditions under which the dereference will take place

 *

 * Perform swap(@rcu_ptr, @ptr) where @rcu_ptr is an RCU-annotated pointer and

 * @c is the argument that is passed to the rcu_dereference_protected() call

 * used to read that pointer.

 */

#define rcu_swap_protected(rcu_ptr, ptr, c) do {			\

	typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c));	\

	rcu_assign_pointer((rcu_ptr), (ptr));				\

	(ptr) = __tmp;							\

} while (0)



/**

 * rcu_access_pointer() - fetch RCU pointer with no dereferencing

 * @p: The pointer to read