On 2024/03/20 8:24, Andrew Morton wrote:
> On Tue, 19 Mar 2024 19:32:11 +0100 Oscar Salvador <osalvador@xxxxxxx> wrote:
>> -static void dec_stack_record_count(depot_stack_handle_t handle)
>> +static void dec_stack_record_count(depot_stack_handle_t handle,
>> + int nr_base_pages)
>> {
>> struct stack_record *stack_record = __stack_depot_get_stack_record(handle);
>>
>> if (stack_record)
>> - refcount_dec(&stack_record->count);
>> + refcount_sub_and_test(nr_base_pages, &stack_record->count);
>> }
>
> mm/page_owner.c: In function 'dec_stack_record_count':
> mm/page_owner.c:226:17: error: ignoring return value of 'refcount_sub_and_test' declared with attribute 'warn_unused_result' [-Werror=unused-result]
> 226 | refcount_sub_and_test(nr_base_pages, &stack_record->count);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>
Hmm, I guess that this is not an expected user of refcount API.
If it is correct behavior that refcount becomes 0 here, you need to explain like
- refcount_sub_and_test(nr_base_pages, &stack_record->count);
+ if (refcount_sub_and_test(nr_base_pages, &stack_record->count)) {
+ // Explain why nothing to do here, and explain where/how
+ // refcount again becomes positive value using refcount_set().
+ }
or replace refcount_t with atomic_t where it is legal to make refcount positive
without using atomic_set().
