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 <[email protected]> Cc: Peter Zijlstra <[email protected]> Reported-by: Jann Horn <[email protected]> Signed-off-by: Will Deacon <[email protected]> --- Applies on top of the READ_ONCE() pile I sent last night (v5). include/linux/compiler.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 741c93c62ecf..e24cc3a2bc3e 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -384,9 +384,9 @@ static inline void *offset_to_ptr(const int *off) /* * Yes, this permits 64-bit accesses on 32-bit architectures. These will - * actually be atomic in many cases (namely x86), but for others we rely on - * the access being split into 2x32-bit accesses for a 32-bit quantity (e.g. - * a virtual address) and a strong prevailing wind. + * actually be atomic in some cases (namely Armv7 + LPAE), but for others we + * rely on the access being split into 2x32-bit accesses for a 32-bit quantity + * (e.g. a virtual address) and a strong prevailing wind. */ #define compiletime_assert_rwonce_type(t) \ compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ -- 2.26.2.645.ge9eca65c58-goog
