Re: [PATCH 1/1] io_uring: fix exiting io_req_task_work_add leaks

[Jens Axboe <axboe@kernel.dk>]

On 7/1/21 6:26 AM, Pavel Begunkov wrote:
> If one entered io_req_task_work_add() not seeing PF_EXITING, it will set
> a ->task_state bit and try task_work_add(), which may fail by that
> moment. If that happens the function would try to cancel the request.
> 
> However, in a meanwhile there might come other io_req_task_work_add()
> callers, which will see the bit set and leave their requests in the
> list, which will never be executed.
> 
> Don't propagate an error, but clear the bit first and then fallback
> all requests that we can splice from the list. The callback functions
> have to be able to deal with PF_EXITING, so poll and apoll was modified
> via changing io_poll_rewait().
> 
> Reported-by: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
> 
> Jens, can you try if it helps with the leak you meantioned? I can't
> see it. As with previous, would need to remove the PF_EXITING check,
> and should be in theory safe to do.

Probably misunderstanding you here, but you already killed the one that
patch 3 remove. In any case, I tested this on top of 1+2, and I don't
see any leaks at that point.


-- 
Jens Axboe