On 6/30/21 11:11 PM, Jens Axboe wrote: > On 6/30/21 4:10 PM, Pavel Begunkov wrote: >> 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? > > I double checked, and seems fine with those two alone. Ran the test > twice, saw massive amounts of leaks with patches 1-3, and none with > patches 1-2 only. I think there is a problem with the failing path of io_req_task_work_add(), the removing back part. Will send a patch tomorrow, but not able to test. -- Pavel Begunkov
