Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux
Pull ACCESS_ONCE() rule tightening from Christian Borntraeger: "Tighten rules for ACCESS_ONCE This series tightens the rules for ACCESS_ONCE to only work on scalar types. It also contains the necessary fixups as indicated by build bots of linux-next. Now everything is in place to prevent new non-scalar users of ACCESS_ONCE and we can continue to convert code to READ_ONCE/WRITE_ONCE" * tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/borntraeger/linux: kernel: Fix sparse warning for ACCESS_ONCE next: sh: Fix compile error kernel: tighten rules for ACCESS ONCE mm/gup: Replace ACCESS_ONCE with READ_ONCE x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE ppc/hugetlbfs: Replace ACCESS_ONCE with READ_ONCE ppc/kvm: Replace ACCESS_ONCE with READ_ONCE
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@@ -451,12 +451,23 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
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* to make the compiler aware of ordering is to put the two invocations of
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* ACCESS_ONCE() in different C statements.
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*
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* This macro does absolutely -nothing- to prevent the CPU from reordering,
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* merging, or refetching absolutely anything at any time. Its main intended
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* use is to mediate communication between process-level code and irq/NMI
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* handlers, all running on the same CPU.
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* ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
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* on a union member will work as long as the size of the member matches the
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* size of the union and the size is smaller than word size.
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*
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* The major use cases of ACCESS_ONCE used to be (1) Mediating communication
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* between process-level code and irq/NMI handlers, all running on the same CPU,
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* and (2) Ensuring that the compiler does not fold, spindle, or otherwise
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* mutilate accesses that either do not require ordering or that interact
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* with an explicit memory barrier or atomic instruction that provides the
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* required ordering.
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*
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* If possible use READ_ONCE/ASSIGN_ONCE instead.
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*/
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#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
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#define __ACCESS_ONCE(x) ({ \
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__maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
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(volatile typeof(x) *)&(x); })
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#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
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/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
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#ifdef CONFIG_KPROBES
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