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Commit bd3fd451 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 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"
parents f28535c1 112dc0c8

drivers/gpu/drm/drm_fb_helper.c

+1 −1
Original line number Diff line number Diff line
@@ -464,7 +464,7 @@ static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper) 


	/* Sometimes user space wants everything disabled, so don't steal the

	 * display if there's a master. */

	if (lockless_dereference(dev->master))

	if (READ_ONCE(dev->master))

		return false;



	drm_for_each_crtc(crtc, dev) {

include/linux/compiler.h

+3 −3
Original line number Diff line number Diff line
@@ -527,13 +527,13 @@ 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 void * variable is to validate @p is indeed a pointer

 * type. All pointer types silently cast to void *.

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

 * type by making sure it can be dereferenced.

 */

#define lockless_dereference(p) \

({ \

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

	__maybe_unused const void * const _________p2 = _________p1; \

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

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

	(_________p1); \

})