The patch below does not apply to the 5.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 997135017716c33f3405e86cca5da9567b40a08e Mon Sep 17 00:00:00 2001

From: Olivier Langlois olivier@trillion01.com Date: Wed, 23 Jun 2021 11:50:11 -0700 Subject: [PATCH] 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.

Cc: stable@vger.kernel.org Signed-off-by: Olivier Langlois olivier@trillion01.com Reviewed-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/d1419dc32ec6a97b453bee34dc03fa6a02797142.162447320... Signed-off-by: Jens Axboe axboe@kernel.dk

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);