lkml.org 
[lkml]   [2016]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH tip/core/rcu 07/12] rcu: No ordering for rcu_assign_pointer() of NULL
Date
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@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
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 c61b6b9506e7..9be61e47badc 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
--
2.5.2
\
 
 \ /
  Last update: 2016-06-16 00:41    [W:0.103 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site