Re: [XEN PATCH] xen: fix violations of MISRA C:2012 Rule 3.1

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

> On 12 Jul 2023, at 16:54, Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx> wrote:
> 
> In the file 'xen/common/xmalloc_tlsf.c' is not clear how
> the commented-out code should interact with the previous statement.
> To resolve the MISRA violation generated by the nested comment
> a #if .. #endif block with an explanatory comment substitutes
> the earlier construct.
> 
> In the file 'xen/include/xen/atomic.h' the nested comment has been removed,
> since the code sample is already explained by the preceding comment.
> 
> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> ---
> Following the suggestion of this message
> https://lore.kernel.org/xen-devel/536f3049-41f7-b127-ba94-81925e34ea0f@xxxxxxxx/
> an explanatory comment has been added.
> ---
> xen/common/xmalloc_tlsf.c | 13 ++++++++++---
> xen/include/xen/atomic.h  |  2 +-
> 2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
> index c21bf71e88..56c3849414 100644
> --- a/xen/common/xmalloc_tlsf.c
> +++ b/xen/common/xmalloc_tlsf.c
> @@ -139,10 +139,17 @@ static inline void MAPPING_SEARCH(unsigned long *r, int 
> *fl, int *sl)
>         *r = *r + t;
>         *fl = flsl(*r) - 1;
>         *sl = (*r >> (*fl - MAX_LOG2_SLI)) - MAX_SLI;
> -        *fl -= FLI_OFFSET;
> -        /*if ((*fl -= FLI_OFFSET) < 0) // FL will be always >0!
> -         *fl = *sl = 0;
> +        /* 
> +         * It's unclear what was the purpose of the commented-out code that 
> now
> +         * is in the #else branch. The current form is motivated by the 
> correction
> +         * of a violation MISRA:C 2012 Rule 3.1
>          */
> +#if 1
> +        *fl -= FLI_OFFSET;
> +#else
> +        if ((*fl -= FLI_OFFSET) < 0) // FL will be always >0!

In the message you linked above, you suggested to use /* FL will be always >0! 
*/, why has it changed?
Was some comment I missed? The xen codestyle mandates the use of /* */, anyway 
I agree that here you
are just moving code...
So maybe the maintainer can tell what is the best thing to do here.

> +          *fl = *sl = 0;
> +#endif
>         *r &= ~t;
>     }
> }
> diff --git a/xen/include/xen/atomic.h b/xen/include/xen/atomic.h
> index 529213ebbb..fa750a18ae 100644
> --- a/xen/include/xen/atomic.h
> +++ b/xen/include/xen/atomic.h
> @@ -78,7 +78,7 @@ static inline void _atomic_set(atomic_t *v, int i);
>  *      int old = atomic_read(&v);
>  *      int new = old + 1;
>  *      if ( likely(old == atomic_cmpxchg(&v, old, new)) )
> - *          break; // success!
> + *          break;
>  *  }
>  */
> static inline int atomic_cmpxchg(atomic_t *v, int old, int new);
> -- 
> 2.34.1
> 
> 

Anyway apart from that, the patch looks ok to me.

Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>