Re: [PATCH 3/3] io_uring: tweak io_req_task_work_add

[Jens Axboe <axboe@kernel.dk>]

On 6/30/21 3:19 PM, Pavel Begunkov wrote:
> On 6/30/21 10:17 PM, Jens Axboe wrote:
>> On 6/30/21 2:54 PM, Pavel Begunkov wrote:
>>> Whenever possible we don't want to fallback a request. task_work_add()
>>> will be fine if the task is exiting, so don't check for PF_EXITING,
>>> there is anyway only a relatively small gap between setting the flag
>>> and doing the final task_work_run().
>>>
>>> Also add likely for the hot path.
>>
>> I'm not a huge fan of likely/unlikely, and in particular constructs like:
>>
>>> -	if (test_bit(0, &tctx->task_state) ||
>>> +	if (likely(test_bit(0, &tctx->task_state)) ||
>>>  	    test_and_set_bit(0, &tctx->task_state))
>>>  		return 0;
>>
>> where the state is combined. In any case, it should be a separate
>> change. If there's an "Also" paragraph in a patch, then that's also
>> usually a good clue that that particular change should've been
>> separate :-)
> 
> Not sure what's wrong with likely above, but how about drop
> this one then?

Yep I did - we can do the exiting change separately, the commit message
just needs to be clarified a bit on why it's ok to do now. And that
last sentence dropped, of course.

-- 
Jens Axboe