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

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/30/21 10:56 PM, Jens Axboe wrote:
> On 6/30/21 3:45 PM, Jens Axboe wrote:
>> On 6/30/21 3:38 PM, Pavel Begunkov wrote:
>>> On 6/30/21 10:22 PM, Jens Axboe wrote:
>>>> 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
>>>
>>> I think 1-2 is good enough for 5.14, I'll just send it for-next
>>>
>>>> just needs to be clarified a bit on why it's ok to do now. And that
>>>
>>> It should have been ok to do before those 2 patches, but
>>> haven't tracked where it lost actuality.
>>
>> Right, I was thinking it was related to the swapping of the signal
>> exit and task work run ordering. But didn't look that far yet...
> 
> BTW, in usual testing, even just the one hunk removing the exit check
> seems to result in quite a lot of memory leaks running
> test/poll-mshot-update. So something is funky with the patch.

I guess you're positive that patches 1-2 have nothing to do
with that. Right?

-- 
Pavel Begunkov