Re: [PATCH v1 1/1] x86/percpu: Cast -1 to argument type when comparing in percpu_add_op()

Dave Hansen
2024-10-16T19:43:48Z

On 10/16/24 11:20, Andy Shevchenko wrote:
>> Maybe more readable, but wouldn't it be theoretically buggy for u64?
>> I'm talking about the case when u64 == UINT_MAX, which will be true
>> in your case and false in mine.
>>
>>> const int pao_ID__ = (__builtin_constant_p(val) &&
>>> ((val) == 1 || (int)(val) == -1)) ?
>>>
>>> (int)(val) : 0;
> This code _is_ buggy, thanks to my new test case.
>
> [ 66.161375] pcp -1 (0xffffffffffffffff) != expected 4294967295 (0xffffffff)

Thanks for pointing that out Andy (and Peter too)!