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

[Jens Axboe <axboe@kernel.dk>]

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?

-- 
Jens Axboe