From da579f05ef0faada3559e7faddf761c75cdf85e1 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 14 Jan 2026 16:54:05 +0800 Subject: [PATCH] io_uring: move local task_work in exit cancel loop With IORING_SETUP_DEFER_TASKRUN, task work is queued to ctx->work_llist (local work) rather than the fallback list. During io_ring_exit_work(), io_move_task_work_from_local() was called once before the cancel loop, moving work from work_llist to fallback_llist. However, task work can be added to work_llist during the cancel loop itself. There are two cases: 1) io_kill_timeouts() is called from io_uring_try_cancel_requests() to cancel pending timeouts, and it adds task work via io_req_queue_tw_complete() for each cancelled timeout: 2) URING_CMD requests like ublk can be completed via io_uring_cmd_complete_in_task() from ublk_queue_rq() during canceling, given ublk request queue is only quiesced when canceling the 1st uring_cmd. Since io_allowed_defer_tw_run() returns false in io_ring_exit_work() (kworker != submitter_task), io_run_local_work() is never invoked, and the work_llist entries are never processed. This causes io_uring_try_cancel_requests() to loop indefinitely, resulting in 100% CPU usage in kworker threads. Fix this by moving io_move_task_work_from_local() inside the cancel loop, ensuring any work on work_llist is moved to fallback before each cancel attempt. Cc: stable@vger.kernel.org Fixes: c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN") Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- io_uring/io_uring.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 87a87396e940..b7a077c11c21 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3003,12 +3003,12 @@ static __cold void io_ring_exit_work(struct work_struct *work) mutex_unlock(&ctx->uring_lock); } - if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) - io_move_task_work_from_local(ctx); - /* The SQPOLL thread never reaches this path */ - while (io_uring_try_cancel_requests(ctx, NULL, true, false)) + do { + if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) + io_move_task_work_from_local(ctx); cond_resched(); + } while (io_uring_try_cancel_requests(ctx, NULL, true, false)); if (ctx->sq_data) { struct io_sq_data *sqd = ctx->sq_data; -- 2.47.3