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locking/barriers: Validate lockless_dereference() is used on a pointer type

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Use the type to validate the argument @p is indeed a pointer type.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Paul McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Peter Zijlstra authored and Ingo Molnar committed 2016-06-08 14:22:47 +02:00
1 parent a461d58792
commit 331b6d8c7a
1 file changed
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include/linux/compiler.h
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@@ -545,10 +545,14 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
* Similar to rcu_dereference(), but for situations where the pointed-to
* object's lifetime is managed by something other than RCU. That
* "something other" might be reference counting or simple immortality.
*
* The seemingly unused void * variable is to validate @p is indeed a pointer
* type. All pointer types silently cast to void *.
*/
#define lockless_dereference(p) \
({ \
typeof(p) _________p1 = READ_ONCE(p); \
__maybe_unused const void * const _________p2 = _________p1; \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
(_________p1); \
})