Re: [PATCH 1/1] io_uring/io-wq: close io-wq full-stop gap

[Jens Axboe <axboe@kernel.dk>]

On 5/23/21 8:48 AM, Pavel Begunkov wrote:
> There is an old problem with io-wq cancellation where requests should be
> killed and are in io-wq but are not discoverable, e.g. in @next_hashed
> or @linked vars of io_worker_handle_work(). It adds some unreliability
> to individual request canellation, but also may potentially get
> __io_uring_cancel() stuck. For instance:
> 
> 1) An __io_uring_cancel()'s cancellation round have not found any
>    request but there are some as desribed.
> 2) __io_uring_cancel() goes to sleep
> 3) Then workers wake up and try to execute those hidden requests
>    that happen to be unbound.
> 
> As we already cancel all requests of io-wq there, set IO_WQ_BIT_EXIT
> in advance, so preventing 3) from executing unbound requests. The
> workers will initially break looping because of getting a signal as they
> are threads of the dying/exec()'ing user task.

Applied, thanks.

-- 
Jens Axboe