Re: [External] : Re: [PATCH] io_uring: fix incorrect unlikely() usage in io_waitid_prep()

[ALOK TIWARI <alok.a.tiwari@oracle.com>]

On 10/17/2025 8:52 PM, Caleb Sander Mateos wrote:
> On Fri, Oct 17, 2025 at 5:41 AM Alok Tiwari<alok.a.tiwari@oracle.com> wrote:
>> The negation operator incorrectly places outside the unlikely() macro:
>>
>>      if (!unlikely(iwa))
>>
>> This caused the compiler hint to be applied to the constant result
>> of the negation rather than the pointer check itself.
> Not sure what you mean by "constant". But yes, applying !unlikely(iwa)
> inverts the hint, saying iwa is unlikely to be non-NULL and therefore
> the if branch is likely. It certainly seems more likely that the whole
> if condition was meant to me marked unlikely.
> 
> Best,
> Caleb
> 

Thanks Caleb.
you are right, "constant result" was a misleading choice of words.
I will update commit message and send a v2 patch.

>> Fix it by moving the negation inside unlikely(), matching the usual
>> kernel pattern:
>>
>>      if (unlikely(!iwa))
>>
>> Fixes: 2b4fc4cd43f2 ("io_uring/waitid: setup async data in the prep handler")
>> Signed-off-by: Alok Tiwari<alok.a.tiwari@oracle.com>
>> ---
>>   io_uring/waitid.c | 2 +-


Thanks,
Alok