On 10/24/25 10:01 AM, Eelco Chaudron wrote:
>
>
> On 17 Oct 2025, at 19:11, Ilya Maximets wrote:
>
>> '-Wuninitialized-const-pointer' complains about passing uninitialized
>> data into a function via a const pointer. That's a valid concern,
>> since normally the function accepting a const argument wouldn't write
>> to it, but will likely use the data.
>>
>> However, we do have some cases of such a coding pattern in OVS today
>> and they generate a ton of warnings with clang 21.
>>
>> The main offenders of this are all the types of locks in OVS: mutex,
>> rwlock, spinlock. All the locking functions accept const pointers
>> and then do a CONST_CAST inside. This is useful for the cases where
>> we have a lock protecting a structure and want to have some read-only
>> function that accepts this structure, e.g.:
>>
>> struct my_type {
>> struct ovs_mutex mutex;
>> int value;
>> };
>>
>> int get_value(const struct my_type *p)
>> {
>> int res;
>>
>> ovs_mutex_lock(&p->mutex);
>> res = p->value;
>> ovs_mutex_unlock(&p->mutex);
>>
>> return res;
>> }
>>
>> If the ovs_mutex_lock() required non-const argument, then we'd have
>> to use CONST_CAST for every lock/unlock, or we would have to make the
>> original pointer 'p' non-const, cascading the change through all the
>> callers of this "read-only" functions.
>>
>> However, it's totally reasonable for the mutex init and destroy to
>> not have a constant argument, since we're explicitly trying to change
>> it and the initialization and destruction likely not happening for
>> the constant parent structure.
>>
>> Let's convert both init and destroy API for all the locks to accept
>> non-const arguments. This makes clang happy as we're no longer
>> passing in the uninitialized locks as const.
>>
>> This technically changes the API, but we're relaxing the restriction,
>> so it shouldn't be a concern. All the code that used these functions
>> before should still work fine.
>>
>> Signed-off-by: Ilya Maximets <[email protected]>
>
> Thanks for the change Ilya, it makes sense to me.
>
> Acked-by: Eelco Chaudron <[email protected]>
>
Thanks! Applied and backported down to 3.3.
Best regards, Ilya Maximets.
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