From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EAF9C4167B for ; Wed, 28 Dec 2022 13:12:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232081AbiL1NMB (ORCPT ); Wed, 28 Dec 2022 08:12:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232653AbiL1NLt (ORCPT ); Wed, 28 Dec 2022 08:11:49 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8989911838 for ; Wed, 28 Dec 2022 05:11:47 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id BBCF8CE12E3 for ; Wed, 28 Dec 2022 13:11:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D238C433EF; Wed, 28 Dec 2022 13:11:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672233103; bh=8vuFPe8exqfGSL5Zn+2FOHbriws4cgM7qprtftQykXg=; h=Subject:To:Cc:From:Date:From; b=xa8aiA2FFX2efU1IZZ2ChYdaCiHSseL2KVF0QmH5EpeQug7J2pGNUgfzhbI3UDwvw P/LP77XxMLKH/YX9qwX9fJY3UaB35Kmcf0fnoQXVmYFTRFYT9Z8JMaSoxp+bCSGPaI uOZzkWJL/lzRMXdKT8yHhPcB9I0fIiqMzMBHqstE= Subject: FAILED: patch "[PATCH] io_uring: pass in EPOLL_URING_WAKE for eventfd signaling and" failed to apply to 6.0-stable tree To: axboe@kernel.dk Cc: From: Date: Wed, 28 Dec 2022 14:11:40 +0100 Message-ID: <16722331001489@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 6.0-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 . Possible dependencies: 4464853277d0 ("io_uring: pass in EPOLL_URING_WAKE for eventfd signaling and wakeups") fc86f9d3bb49 ("io_uring: remove redundant memory barrier in io_req_local_work_add") 21a091b970cd ("io_uring: signal registered eventfd to process deferred task work") d8e9214f119d ("io_uring: move io_eventfd_put") c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN") b4c98d59a787 ("io_uring: introduce io_has_work") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4464853277d0ccdb9914608dd1332f0fa2f9846f Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sun, 20 Nov 2022 10:18:45 -0700 Subject: [PATCH] io_uring: pass in EPOLL_URING_WAKE for eventfd signaling and wakeups Pass in EPOLL_URING_WAKE when signaling eventfd or doing poll related wakups, so that we can check for a circular event dependency between eventfd and epoll. If this flag is set when our wakeup handlers are called, then we know we have a dependency that needs to terminate multishot requests. eventfd and epoll are the only such possible dependencies. Cc: stable@vger.kernel.org # 6.0 Signed-off-by: Jens Axboe diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 1299f9c8567a..762ecab801f2 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -495,7 +495,7 @@ static void io_eventfd_ops(struct rcu_head *rcu) int ops = atomic_xchg(&ev_fd->ops, 0); if (ops & BIT(IO_EVENTFD_OP_SIGNAL_BIT)) - eventfd_signal(ev_fd->cq_ev_fd, 1); + eventfd_signal_mask(ev_fd->cq_ev_fd, 1, EPOLL_URING_WAKE); /* IO_EVENTFD_OP_FREE_BIT may not be set here depending on callback * ordering in a race but if references are 0 we know we have to free @@ -531,7 +531,7 @@ static void io_eventfd_signal(struct io_ring_ctx *ctx) goto out; if (likely(eventfd_signal_allowed())) { - eventfd_signal(ev_fd->cq_ev_fd, 1); + eventfd_signal_mask(ev_fd->cq_ev_fd, 1, EPOLL_URING_WAKE); } else { atomic_inc(&ev_fd->refs); if (!atomic_fetch_or(BIT(IO_EVENTFD_OP_SIGNAL_BIT), &ev_fd->ops)) diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index 69fbd27c7577..83013ee584d6 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -4,6 +4,7 @@ #include #include #include +#include #include "io-wq.h" #include "slist.h" #include "filetable.h" @@ -211,12 +212,18 @@ static inline void io_commit_cqring(struct io_ring_ctx *ctx) static inline void __io_cqring_wake(struct io_ring_ctx *ctx) { /* - * wake_up_all() may seem excessive, but io_wake_function() and - * io_should_wake() handle the termination of the loop and only - * wake as many waiters as we need to. + * Trigger waitqueue handler on all waiters on our waitqueue. This + * won't necessarily wake up all the tasks, io_should_wake() will make + * that decision. + * + * Pass in EPOLLIN|EPOLL_URING_WAKE as the poll wakeup key. The latter + * set in the mask so that if we recurse back into our own poll + * waitqueue handlers, we know we have a dependency between eventfd or + * epoll and should terminate multishot poll at that point. */ if (waitqueue_active(&ctx->cq_wait)) - wake_up_all(&ctx->cq_wait); + __wake_up(&ctx->cq_wait, TASK_NORMAL, 0, + poll_to_key(EPOLL_URING_WAKE | EPOLLIN)); } static inline void io_cqring_wake(struct io_ring_ctx *ctx) diff --git a/io_uring/poll.c b/io_uring/poll.c index 8fb8e781c02d..22c9b2e0944a 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -389,6 +389,14 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, return 0; if (io_poll_get_ownership(req)) { + /* + * If we trigger a multishot poll off our own wakeup path, + * disable multishot as there is a circular dependency between + * CQ posting and triggering the event. + */ + if (mask & EPOLL_URING_WAKE) + poll->events |= EPOLLONESHOT; + /* optional, saves extra locking for removal in tw handler */ if (mask && poll->events & EPOLLONESHOT) { list_del_init(&poll->wait.entry);