Re: [Minios-devel] [UNIKRAFT PATCH 1/4] include/uk: do not cast away volatile in atomic.h

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

Hi Yuri,

thanks for revisiting this.


On 10/05/2018 10:21 AM, Yuri Volchkov wrote:
> Many functions in include/uk/arch/atomic.h accept a volatile argument
> and then cast it to something like "__u8 *". In many cases it is ok,
> __atomic_*() is called inside the function. But in other cases, this
> memory access is a subject to compiler optimization, and may lead to
> an unexpected behavior.
>
> Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
Reviewed-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
> ---
>   include/uk/arch/atomic.h | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/uk/arch/atomic.h b/include/uk/arch/atomic.h
> index d4abeb7..0964e14 100644
> --- a/include/uk/arch/atomic.h
> +++ b/include/uk/arch/atomic.h
> @@ -96,7 +96,7 @@ extern "C" {
>    */
>   static inline int ukarch_test_and_clr_bit(unsigned int nr, volatile void 
> *byte)
>   {
> -       __u8 *addr = ((__u8 *)byte) + (nr >> 3);
> +       volatile __u8 *addr = ((__u8 *)byte) + (nr >> 3);
>         __u8 bit = 1 << (nr & 7);
>         __u8 orig;
>   
> @@ -111,7 +111,7 @@ static inline int ukarch_test_and_clr_bit(unsigned int nr, volatile void *byte)
>    */
>   static inline int ukarch_test_and_set_bit(unsigned int nr, volatile void 
> *byte)
>   {
> -       __u8 *addr = ((__u8 *)byte) + (nr >> 3);
> +       volatile __u8 *addr = ((__u8 *)byte) + (nr >> 3);
>         __u8 bit = 1 << (nr & 7);
>         __u8 orig;
>   
> @@ -126,7 +126,7 @@ static inline int ukarch_test_and_set_bit(unsigned int nr, volatile void *byte)
>   static inline int ukarch_test_bit(unsigned int nr,
>                                         const volatile unsigned long *byte)
>   {
> -       const __u8 *ptr = (const __u8 *)byte;
> +       const volatile __u8 *ptr = (const __u8 *)byte;
>   
>   	return ((1 << (nr & 7)) & (ptr[nr >> 3])) != 0;
>   }
> @@ -154,7 +154,7 @@ static inline void ukarch_clr_bit(unsigned int nr,
>   static inline int ukarch_test_and_clr_bit_sync(unsigned int nr,
>                                                 volatile void *byte)
>   {
> -       __u8 *addr = ((__u8 *)byte) + (nr >> 3);
> +       volatile __u8 *addr = ((__u8 *)byte) + (nr >> 3);
>         __u8 bit = 1 << (nr & 7);
>         __u8 orig;
>   
> @@ -167,7 +167,7 @@ static inline int ukarch_test_and_clr_bit_sync(unsigned int nr,
>   static inline int ukarch_test_and_set_bit_sync(unsigned int nr,
>                                                 volatile void *byte)
>   {
> -       __u8 *addr = ((__u8 *)byte) + (nr >> 3);
> +       volatile __u8 *addr = ((__u8 *)byte) + (nr >> 3);
>         __u8 bit = 1 << (nr & 7);
>         __u8 orig;
>   
--
Dr. Florian Schmidt
フローリアン・シュミット
Research Scientist,
Systems and Machine Learning Group
NEC Laboratories Europe
Kurfürsten-Anlage 36, D-69115 Heidelberg
Tel.     +49 (0)6221 4342-265
Fax:     +49 (0)6221 4342-155
e-mail:  florian.schmidt@xxxxxxxxx
============================================================
Registered at Amtsgericht Mannheim, Germany, HRB728558

_______________________________________________
Minios-devel mailing list
Minios-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/minios-devel