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Subject[PATCH tip/core/rcu 3/9] rcu: Make kfree_rcu() ignore NULL pointers
Date
This commit makes the kfree_rcu() macro's semantics be consistent
with the likes of kfree() by adding a check for NULL pointers, so
that kfree_rcu(NULL, ...) is a no-op.

Reported-by: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
Reported-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
---
include/linux/rcupdate.h | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 922bb6848813..915460ec0872 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -805,7 +805,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
/**
* kfree_rcu() - kfree an object after a grace period.
* @ptr: pointer to kfree
- * @rcu_head: the name of the struct rcu_head within the type of @ptr.
+ * @rhf: the name of the struct rcu_head within the type of @ptr.
*
* Many rcu callbacks functions just call kfree() on the base structure.
* These functions are trivial, but their size adds up, and furthermore
@@ -828,9 +828,13 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
* The BUILD_BUG_ON check must not involve any function calls, hence the
* checks are done in macros here.
*/
-#define kfree_rcu(ptr, rcu_head) \
- __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
-
+#define kfree_rcu(ptr, rhf) \
+do { \
+ typeof (ptr) ___p = (ptr); \
+ \
+ if (___p) \
+ __kfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
+} while (0)

/*
* Place this after a lock-acquisition primitive to guarantee that
--
2.17.1
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