Re: [PATCH 1/1] io_uring: replace inflight_wait with tctx->wait

[Jens Axboe <axboe@kernel.dk>]

On 11/16/20 9:48 AM, Pavel Begunkov wrote:
> On 16/11/2020 16:33, Jens Axboe wrote:
>> On 11/15/20 5:56 AM, Pavel Begunkov wrote:
>>> As tasks now cancel only theirs requests, and inflight_wait is awaited
>>> only in io_uring_cancel_files(), which should be called with ->in_idle
>>> set, instead of keeping a separate inflight_wait use tctx->wait.
>>>
>>> That will add some spurious wakeups but actually is safer from point of
>>> not hanging the task.
>>>
>>> e.g.
>>> task1                   | IRQ
>>>                         | *start* io_complete_rw_common(link)
>>>                         |        link: req1 -> req2 -> req3(with files)
>>> *cancel_files()         |
>>> io_wq_cancel(), etc.    |
>>>                         | put_req(link), adds to io-wq req2
>>> schedule()              |
>>>
>>> So, task1 will never try to cancel req2 or req3. If req2 is
>>> long-standing (e.g. read(empty_pipe)), this may hang.
>>
>> This looks like it's against 5.11, but also looks like we should add
>> it for 5.10?
> 
> Yeah, 5.10 completely slipped my mind, I'll resend

I applied it to 5.10, and fixed up the 5.11 side of things. So all good,
just wanted to confirm.

-- 
Jens Axboe