Re: [PATCH 12/12] io_uring: improve in tctx_task_work() resubmission

[Jens Axboe <axboe@kernel.dk>]

On 6/17/21 11:14 AM, Pavel Begunkov wrote:
> If task_state is cleared, io_req_task_work_add() will go the slow path
> adding a task_work, setting the task_state, waking up the task and so
> on. Not to mention it's expensive. tctx_task_work() first clears the
> state and then executes all the work items queued, so if any of them
> resubmits or adds new task_work items, it would unnecessarily go through
> the slow path of io_req_task_work_add().
> 
> Let's clear the ->task_state at the end. We still have to check
> ->task_list for emptiness afterward to synchronise with
> io_req_task_work_add(), do that, and set the state back if we're going
> to retry, because clearing not-ours task_state on the next iteration
> would be buggy.

Are we not re-introducing the problem fixed by 1d5f360dd1a3c by swapping
these around?

-- 
Jens Axboe