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

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

[Olivier Langlois]

[ 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 <olivier@trillion01.com>
---
 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

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

[Jens Axboe]

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

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

[Greg KH]

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