From 49ae66eb8c27375075ffa308cfd4bf25af335d41 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 11 May 2026 10:58:50 -0600 Subject: [PATCH] io_uring: defer linked-timeout chain splice out of hrtimer context io_link_timeout_fn() is the hrtimer callback that fires when a linked timeout expires. It currently calls io_remove_next_linked(prev) under ctx->timeout_lock to splice the timeout request out of the link chain. This is the only chain-mutation site that runs without ctx->uring_lock, because hrtimer callbacks cannot take a mutex. Defer the splicing until the task_work callback. Signed-off-by: Jens Axboe --- io_uring/timeout.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/io_uring/timeout.c b/io_uring/timeout.c index e2595cae2b07..6353a4d979dc 100644 --- a/io_uring/timeout.c +++ b/io_uring/timeout.c @@ -284,6 +284,10 @@ static struct io_kiocb *__io_disarm_linked_timeout(struct io_kiocb *req, struct io_timeout *timeout = io_kiocb_to_cmd(link, struct io_timeout); io_remove_next_linked(req); + + /* If this is NULL, then timer already claimed it and will complete it */ + if (!timeout->head) + return NULL; timeout->head = NULL; if (hrtimer_try_to_cancel(&io->timer) != -1) { list_del(&timeout->list); @@ -367,6 +371,14 @@ static void io_req_task_link_timeout(struct io_tw_req tw_req, io_tw_token_t tw) int ret; if (prev) { + /* + * splice the linked timeout out of prev's chain if the regular + * completion path didn't already do it. + */ + if (prev->link == req) + prev->link = req->link; + req->link = NULL; + if (!tw.cancel) { struct io_cancel_data cd = { .ctx = req->ctx, @@ -401,10 +413,10 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer) /* * We don't expect the list to be empty, that will only happen if we - * race with the completion of the linked work. + * race with the completion of the linked work. Splice of prev is + * done in io_req_task_link_timeout(), if needed. */ if (prev) { - io_remove_next_linked(prev); if (!req_ref_inc_not_zero(prev)) prev = NULL; }