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To:     Christian Borntraeger <borntraeger@de.ibm.com>
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        Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH/RFC 7/7] kernel: Force ACCESS_ONCE to work only on scalar types
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From:   David Howells <dhowells@redhat.com>
Date:   Mon, 24 Nov 2014 13:30:58 +0000
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Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> +#define get_scalar_volatile_pointer(x) ({ \
> +	typeof(x) *__p = &(x); \
> +	volatile typeof(x) *__vp = __p; \
> +	(void)(long)*__p; __vp; })
> +#define ACCESS_ONCE(x) (*get_scalar_volatile_pointer(x))

Might this cause two loads from memory under some conditions?  Once for the
fourth line and once for the fifth?

(Apologies if this has already been discussed)

David