Commit-ID: 3a37f7275cda5ad25c1fe9be8f20c76c60d175fa
Gitweb: http://git.kernel.org/tip/3a37f7275cda5ad25c1fe9be8f20c76c60d175fa
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Sun, 1 May 2016 18:46:54 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Wed, 15 Jun 2016 15:31:28 -0700
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: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
include/linux/rcupdate.h | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c61b6b9..a8af797 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -650,7 +650,16 @@ static inline void rcu_preempt_sleep_check(void)
* please be careful when making changes to rcu_assign_pointer() and the
* 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
--
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