Re: [XEN PATCH 3/7] xen/sched: address a violation of MISRA C:2012 Rule 16.3

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.04.2024 09:22, Federico Serafini wrote:
> Use pseudo-keyword fallthrough to meet the requirements to deviate
> MISRA C:2012 Rule 16.3 ("An unconditional `break' statement shall
> terminate every switch-clause").
> 
> No functional change.
> 
> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> ---
>  xen/common/sched/credit2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/common/sched/credit2.c b/xen/common/sched/credit2.c
> index c76330d79d..0962b52415 100644
> --- a/xen/common/sched/credit2.c
> +++ b/xen/common/sched/credit2.c
> @@ -3152,8 +3152,8 @@ static int cf_check csched2_sys_cntl(
>              printk(XENLOG_INFO "Disabling context switch rate limiting\n");
>          prv->ratelimit_us = params->ratelimit_us;
>          write_unlock_irqrestore(&prv->lock, flags);
> +        fallthrough;
>  
> -    /* FALLTHRU */
>      case XEN_SYSCTL_SCHEDOP_getinfo:
>          params->ratelimit_us = prv->ratelimit_us;
>          break;

Hmm, the description doesn't say what's wrong with the comment. Furthermore
docs/misra/rules.rst doesn't mention "fallthrough" at all, nor the
alternative of using comments. I notice docs/misra/deviations.rst does, and
there the specific comment used here isn't covered. That would want saying
in the description.

Stefano (and others) - in this context it becomes noticeable that having
stuff scattered across multiple doc files isn't necessarily helpful. Other
permissible keywords are mentioned in rules.rst. The pseudo-keyword
"fallthrough" as well as comments are mentioned on deviations.rst. Could
you remind me of the reason(s) why things aren't recorded in a single,
central place?

Jan