READ_ONCE: Fix comment describing 2x32-bit atomicity
READ_ONCE() permits 64-bit accesses on 32-bit architectures, since this crops up in a few places and is generally harmless because either the upper bits are always zero (e.g. for a virtual address or 32-bit time_t) or the architecture provides 64-bit atomicity anyway. Update the corresponding comment above compiletime_assert_rwonce_type(), which incorrectly states that 32-bit x86 provides 64-bit atomicity, and instead reference 32-bit Armv7 with LPAE. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Will Deacon <will@kernel.org>
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@ -332,9 +332,9 @@ static inline void *offset_to_ptr(const int *off)
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/*
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* Yes, this permits 64-bit accesses on 32-bit architectures. These will
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* actually be atomic in many cases (namely x86), but for others we rely on
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* the access being split into 2x32-bit accesses for a 32-bit quantity (e.g.
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* a virtual address) and a strong prevailing wind.
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* actually be atomic in some cases (namely Armv7 + LPAE), but for others we
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* rely on the access being split into 2x32-bit accesses for a 32-bit quantity
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* (e.g. a virtual address) and a strong prevailing wind.
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*/
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#define compiletime_assert_rwonce_type(t) \
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compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
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