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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()
This commit is contained in:
Linus Torvalds 2016-09-13 12:13:58 -07:00
parent 7c2c114416 d7127b5e5f
commit 504cb1c25b
1 changed files with 4 additions and 3 deletions
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7
include/linux/compiler.h
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@ -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); \
})