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SubjectRe: [PATCH 3/3] tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h
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On 2016年11月24日 18:25, Mark Rutland wrote:
> As a step towards killing off ACCESS_ONCE, use {READ,WRITE}_ONCE() for the
> virtio tools uaccess primitives, pulling these in from <linux/compiler.h>.
>
> With this done, we can kill off the now-unused ACCESS_ONCE() definition.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: virtualization@lists.linux-foundation.org
> ---
> tools/virtio/linux/uaccess.h | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/tools/virtio/linux/uaccess.h b/tools/virtio/linux/uaccess.h
> index 0a578fe..fa05d01 100644
> --- a/tools/virtio/linux/uaccess.h
> +++ b/tools/virtio/linux/uaccess.h
> @@ -1,8 +1,9 @@
> #ifndef UACCESS_H
> #define UACCESS_H
> -extern void *__user_addr_min, *__user_addr_max;
>
> -#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
> +#include <linux/compiler.h>
> +
> +extern void *__user_addr_min, *__user_addr_max;
>
> static inline void __chk_user_ptr(const volatile void *p, size_t size)
> {
> @@ -13,7 +14,7 @@ static inline void __chk_user_ptr(const volatile void *p, size_t size)
> ({ \
> typeof(ptr) __pu_ptr = (ptr); \
> __chk_user_ptr(__pu_ptr, sizeof(*__pu_ptr)); \
> - ACCESS_ONCE(*(__pu_ptr)) = x; \
> + WRITE_ONCE(*(__pu_ptr), x); \
> 0; \
> })
>
> @@ -21,7 +22,7 @@ static inline void __chk_user_ptr(const volatile void *p, size_t size)
> ({ \
> typeof(ptr) __pu_ptr = (ptr); \
> __chk_user_ptr(__pu_ptr, sizeof(*__pu_ptr)); \
> - x = ACCESS_ONCE(*(__pu_ptr)); \
> + x = READ_ONCE(*(__pu_ptr)); \
> 0; \
> })
>

Reviewed-by: Jason Wang <jasowang@redhat.com>

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