Re: [PATCH v2 1/2] io_uring: Fix race condition when sqp thread goes to sleep

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/23/21 7:50 PM, Olivier Langlois wrote:
> 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, the bug should be pretty old.

Cc: stable@vger.kernel.org
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

> Signed-off-by: Olivier Langlois <olivier@trillion01.com>
> ---
>  fs/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index fc8637f591a6..7c545fa66f31 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6902,7 +6902,7 @@ static int io_sq_thread(void *data)
>  		}
>  
>  		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
> -		if (!io_sqd_events_pending(sqd)) {
> +		if (!io_sqd_events_pending(sqd) && !io_run_task_work()) {
>  			needs_sched = true;
>  			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
>  				io_ring_set_wakeup_flag(ctx);
> 

-- 
Pavel Begunkov