2021-07-25 17:49:44

by Olivier Langlois

Subject: [PATCH io_uring backport to 5.13.y] io_uring: Fix race condition when sqp thread goes to sleep

[ Upstream commit 997135017716 ("io_uring: Fix race condition when sqp thread goes to sleep") ]

If an asynchronous completion happens before the task is preparing
itself to wait and set its state to TASK_INTERRUPTIBLE, the completion
will not wake up the sqp thread.

Signed-off-by: Olivier Langlois <[email protected]>
---
fs/io_uring.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index eeea6b8c8bee..a7f1cbd7be9a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6876,7 +6876,8 @@ static int io_sq_thread(void *data)
}

prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
- if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {
+ if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) &&
+ !io_run_task_work()) {
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
io_ring_set_wakeup_flag(ctx);

--
2.32.0

2021-07-25 19:16:01

by Jens Axboe

Subject: Re: [PATCH io_uring backport to 5.13.y] io_uring: Fix race condition when sqp thread goes to sleep

On 7/24/21 11:07 PM, Olivier Langlois wrote:
> [ Upstream commit 997135017716 ("io_uring: Fix race condition when sqp thread goes to sleep") ]
>
> If an asynchronous completion happens before the task is preparing
> itself to wait and set its state to TASK_INTERRUPTIBLE, the completion
> will not wake up the sqp thread.

Looks good to me - Greg, would you mind queueing this one up?

--
Jens Axboe

2021-07-26 07:44:53

by Greg KH

Subject: Re: [PATCH io_uring backport to 5.13.y] io_uring: Fix race condition when sqp thread goes to sleep

On Sun, Jul 25, 2021 at 01:10:22PM -0600, Jens Axboe wrote:
> On 7/24/21 11:07 PM, Olivier Langlois wrote:
> > [ Upstream commit 997135017716 ("io_uring: Fix race condition when sqp thread goes to sleep") ]
> >
> > If an asynchronous completion happens before the task is preparing
> > itself to wait and set its state to TASK_INTERRUPTIBLE, the completion
> > will not wake up the sqp thread.
>
> Looks good to me - Greg, would you mind queueing this one up?
>

Now queued up, thanks!

greg k-h