scsi: rcu: Introduce rcu_swap_protected()
authorBart Van Assche <bart.vanassche@wdc.com>
Tue, 29 Aug 2017 15:50:11 +0000 (08:50 -0700)
committerMartin K. Petersen <martin.petersen@oracle.com>
Wed, 30 Aug 2017 01:51:41 +0000 (21:51 -0400)
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: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Paul 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: Martin K. Petersen <martin.petersen@oracle.com>
include/linux/rcupdate.h

index f816fc72b51eeda73bf55f7d7176b25cdb27f110..8e920f0ecb07ed0b7fa72e7612e4641bc379616e 100644 (file)
@@ -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