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Commit 504cb1c2 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull locking fix from Ingo Molnar:
 "Another lockless_dereference() Sparse fix"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/barriers: Don't use sizeof(void) in lockless_dereference()
parents 7c2c1144 d7127b5e

include/linux/compiler.h

+4 −3
Original line number Diff line number Diff line
@@ -527,13 +527,14 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s 
 * object's lifetime is managed by something other than RCU.  That

 * "something other" might be reference counting or simple immortality.

 *

 * The seemingly unused size_t variable is to validate @p is indeed a pointer

 * type by making sure it can be dereferenced.

 * The seemingly unused variable ___typecheck_p validates that @p is

 * indeed a pointer type by using a pointer to typeof(*p) as the type.

 * Taking a pointer to typeof(*p) again is needed in case p is void *.

 */

#define lockless_dereference(p) \

({ \

	typeof(p) _________p1 = READ_ONCE(p); \

	size_t __maybe_unused __size_of_ptr = sizeof(*(p)); \

	typeof(*(p)) *___typecheck_p __maybe_unused; \

	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \

	(_________p1); \

})