Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE()

On Fri, Nov 25, 2016 at 01:44:04PM +0100, Peter Zijlstra wrote:

On Fri, Nov 25, 2016 at 01:40:44PM +0100, Peter Zijlstra wrote:

quoted

#define SINGLE_LOAD(x)						\
{(								\
	compiletime_assert_atomic_type(typeof(x));		\

Should be:

	compiletime_assert_atomic_type(x);

quoted

	WARN_SINGLE_COPY_ALIGNMENT(&(x));			\

Do we need to worry about the side effect on x? Maybe

#define SINGLE_LOAD(x)					\
({							\
	typeof(x) *_____ptr;				\
							\
	compiletime_assert_atomic_type(typeof(x));	\
							\
	_____ptr = &(x);				\
							\
	WARN_SINGLE_COPY_ALIGNMENT(_____ptr);		\
							\
	READ_ONCE(*_____ptr);				\
})

Ditto for SINGLE_STORE()

Regards,
Boqun

quoted

	READ_ONCE(x);						\
})

#define SINGLE_STORE(x, v)					\
({								\
	compiletime_assert_atomic_type(typeof(x));		\

idem

quoted

	WARN_SINGLE_COPY_ALIGNMENT(&(x));			\
	WRITE_ONCE(x, v);					\
})