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-rw-r--r--include/linux/compiler.h7
1 files changed, 4 insertions, 3 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 436aa4e42221..668569844d37 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -527,13 +527,14 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
527 * object's lifetime is managed by something other than RCU. That 527 * object's lifetime is managed by something other than RCU. That
528 * "something other" might be reference counting or simple immortality. 528 * "something other" might be reference counting or simple immortality.
529 * 529 *
530 * The seemingly unused size_t variable is to validate @p is indeed a pointer 530 * The seemingly unused variable ___typecheck_p validates that @p is
531 * type by making sure it can be dereferenced. 531 * indeed a pointer type by using a pointer to typeof(*p) as the type.
532 * Taking a pointer to typeof(*p) again is needed in case p is void *.
532 */ 533 */
533#define lockless_dereference(p) \ 534#define lockless_dereference(p) \
534({ \ 535({ \
535 typeof(p) _________p1 = READ_ONCE(p); \ 536 typeof(p) _________p1 = READ_ONCE(p); \
536 size_t __maybe_unused __size_of_ptr = sizeof(*(p)); \ 537 typeof(*(p)) *___typecheck_p __maybe_unused; \
537 smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ 538 smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
538 (_________p1); \ 539 (_________p1); \
539}) 540})