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@xxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Cc: Shane M Seymour <shane.seymour@xxxxxxx>
---
include/linux/rcupdate.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f816fc72b51e..8e920f0ecb07 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -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
--
2.14.1
