Pull locking fixes from Ingo Molnar: "Two lockless_dereference() related fixes" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/barriers: Suppress sparse warnings in lockless_dereference() Revert "drm/fb-helper: Reduce READ_ONCE(master) to lockless_dereference"
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| @@ -527,13 +527,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s · 526 unmodified lines | |||
| 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 void * variable is to validate @p is indeed a pointer | 530 | * The seemingly unused size_t variable is to validate @p is indeed a pointer |
| 531 | * type. All pointer types silently cast to void *. | 531 | * type by making sure it can be dereferenced. |
| 532 | */ | 532 | */ |
| 533 | #define lockless_dereference(p) \ | 533 | #define lockless_dereference(p) \ |
| 534 | ({ \ | 534 | ({ \ |
| 535 | typeof(p) _________p1 = READ_ONCE(p); \ | 535 | typeof(p) _________p1 = READ_ONCE(p); \ |
| 536 | __maybe_unused const void * const _________p2 = _________p1; \ | 536 | size_t __maybe_unused __size_of_ptr = sizeof(*(p)); \ |
| 537 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ | 537 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
| 538 | (_________p1); \ | 538 | (_________p1); \ |
| 539 | }) | 539 | }) |