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From: Jan Hendrik Farr <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Pavel Begunkov <[email protected]>,
	io-uring <[email protected]>
Subject: Re: [PATCH] io_uring: run normal task_work AFTER local work
Date: Thu, 19 Sep 2024 20:31:55 +0200	[thread overview]
Message-ID: <ZuxuGwU172K2-Pik@archlinux> (raw)
In-Reply-To: <[email protected]>

On 19 12:06:20, Jens Axboe wrote:
> On 9/19/24 10:47 AM, Jan Hendrik Farr wrote:
> >> [...]
> >>
> >> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> >> index 75f0087183e5..56097627eafc 100644
> >> --- a/io_uring/io_uring.c
> >> +++ b/io_uring/io_uring.c
> >> @@ -2472,7 +2472,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
> >>  		return 1;
> >>  	if (unlikely(!llist_empty(&ctx->work_llist)))
> >>  		return 1;
> >> -	if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL)))
> >> +	if (unlikely(task_work_pending(current)))
> >>  		return 1;
> >>  	if (unlikely(task_sigpending(current)))
> >>  		return -EINTR;
> >> diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
> >> index 9d70b2cf7b1e..2fbf0ea9c171 100644
> >> --- a/io_uring/io_uring.h
> >> +++ b/io_uring/io_uring.h
> >> @@ -308,15 +308,17 @@ static inline int io_run_task_work(void)
> >>  	 */
> >>  	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
> >>  		clear_notify_signal();
> >> +
> >> +	if (test_thread_flag(TIF_NOTIFY_RESUME)) {
> >> +		__set_current_state(TASK_RUNNING);
> >> +		resume_user_mode_work(NULL);
> >> +	}
> >> +
> >>  	/*
> >>  	 * PF_IO_WORKER never returns to userspace, so check here if we have
> >>  	 * notify work that needs processing.
> >>  	 */
> >>  	if (current->flags & PF_IO_WORKER) {
> >> -		if (test_thread_flag(TIF_NOTIFY_RESUME)) {
> >> -			__set_current_state(TASK_RUNNING);
> >> -			resume_user_mode_work(NULL);
> >> -		}
> >>  		if (current->io_uring) {
> >>  			unsigned int count = 0;
> >>  
> >>
> > 
> > Can confirm that also this patch fixes the issue on my end (both with the
> > reordering of the task_work and without it).
> 
> Great, thanks for testing! Sent out a v2. No need to test it unless you
> absolutely want to ;-)
> 
> > Also found a different way to trigger the issue that does not misuse
> > IOSQE_IO_LINK. Do three sends with IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_LINK
> > followed by a close with IOSQE_CQE_SKIP_SUCCESS on a ring with
> > IORING_SETUP_DEFER_TASKRUN.
> > 
> > I confirmed that that test case also first brakes on
> > 846072f16eed3b3fb4e59b677f3ed8afb8509b89 and is fixed by either of the
> > two patches you sent.
> > 
> > Not sure if that's a preferable test case compared to the weirder ealier one.
> > You can find it below as a patch to the existing test case in the liburing
> > repo:
> 
> I think that's an improvement, just because it doesn't rely on a weird
> usage of IOSQE_IO_LINK. And it looks good to me - do you want me to
> commit this directly, or do you want to send a "proper" patch (or github
> PR) to retain the proper attribution to you?
> 

Sent the PR with one minor change (adjusted the user data for the third
send).


  reply	other threads:[~2024-09-19 18:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-18 18:03 [PATCH] io_uring: run normal task_work AFTER local work Jens Axboe
2024-09-19 10:22 ` Pavel Begunkov
2024-09-19 16:00   ` Jens Axboe
2024-09-19 16:47     ` Jan Hendrik Farr
2024-09-19 18:06       ` Jens Axboe
2024-09-19 18:31         ` Jan Hendrik Farr [this message]
2024-09-19 18:32           ` Jens Axboe

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