io_uring: add reschedule point to handle_tw_list()

Commit f586800854 upstream.

If CONFIG_PREEMPT_NONE is set and the task_work chains are long, we
could be running into issues blocking others for too long. Add a
reschedule check in handle_tw_list(), and flush the ctx if we need to
reschedule.

Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

io_uring/io_uring.c

@@ -2214,9 +2214,12 @@ static void tctx_task_work(struct callback_head *cb)
 			}
 			req->io_task_work.func(req, &locked);
 			node = next;
+			if (unlikely(need_resched())) {
+				ctx_flush_and_put(ctx, &locked);
+				ctx = NULL;
+				cond_resched();
+			}
 		} while (node);
-
-		cond_resched();
 	}
 
 	ctx_flush_and_put(ctx, &locked);