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Re: [XEN PATCH] xen/evtchn: address violations of MISRA C:2012 Rules 16.3 and 16.4


  • To: Federico Serafini <federico.serafini@xxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 11 Mar 2024 10:51:15 +0100
  • Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
  • Cc: consulting@xxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 11 Mar 2024 09:51:22 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 11.03.2024 10:02, Federico Serafini wrote:
> On 11/03/24 08:40, Jan Beulich wrote:
>> On 08.03.2024 12:51, Federico Serafini wrote:
>>> --- a/xen/common/event_channel.c
>>> +++ b/xen/common/event_channel.c
>>> @@ -130,9 +130,12 @@ static bool virq_is_global(unsigned int virq)
>>>   
>>>       case VIRQ_ARCH_0 ... VIRQ_ARCH_7:
>>>           return arch_virq_is_global(virq);
>>> +
>>> +    default:
>>> +        ASSERT(virq < NR_VIRQS);
>>> +        break;
>>>       }
>>>   
>>> -    ASSERT(virq < NR_VIRQS);
>>>       return true;
>>>   }
>>
>> Just for my understanding: The ASSERT() is moved so the "default" would
>> consist of more than just "break". Why is it that then the "return" isn't
>> moved, too?
> 
> No reason in particular.
> If preferred, I can move it too.

I for one would prefer that, yes. But what's needed up front is that we
decide what we want to do _consistently_ in all such cases.

>>> @@ -1672,6 +1676,9 @@ static void domain_dump_evtchn_info(struct domain *d)
>>>           case ECS_VIRQ:
>>>               printk(" v=%d", chn->u.virq);
>>>               break;
>>> +        default:
>>> +            /* Nothing to do in other cases. */
>>> +            break;
>>>           }
>>
>> Yes this, just to mention it, while in line with what Misra demands is
>> pretty meaningless imo: The absence of "default" says exactly what the
>> comment now says. FTAOD - this is a comment towards the Misra guideline,
>> not so much towards the specific change here.
> 
> Both you and Stefano reviewed the code and agreed on the fact that doing
> nothing for the default case is the right thing and now the code
> explicitly says that without letting any doubts.
> Furthermore, during the reviews it could happen that you notice a switch
> where something needs to be done for the default case.

That shouldn't happen during review. Anyone proposing a patch to add such
a comment wants to first have made sure the comment is actually applicable
there. Otherwise we're in "mechanically add comments" territory, which I
think we all agreed we want to avoid.

Jan



 


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