From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C01AD28EE for ; Mon, 2 Jan 2023 11:25:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48B87C433EF; Mon, 2 Jan 2023 11:25:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672658729; bh=leZMwv4UwnGNirV/iXK0BUw2HY8AoV6hCzKZ6ViRgPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rQ9Ut1yt7TLOpmdvSZDbzjGPEjZhSV8I6z2Kqj3UD7QRvz0SeUtsymiUZW/yEbFjo umIo4l5Ts9S6c+dMXXa419mzehcBCaNMyXWiVMwf82hSpVuw8EYiexb5eeKUDAH+mj JarQIXD9jN8bwbpC5KoPqYxgf7KDj6RKNvPwb9FE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jens Axboe , Sasha Levin Subject: [PATCH 6.1 03/71] io_uring: pass in EPOLL_URING_WAKE for eventfd signaling and wakeups Date: Mon, 2 Jan 2023 12:21:28 +0100 Message-Id: <20230102110551.650271448@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230102110551.509937186@linuxfoundation.org> References: <20230102110551.509937186@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Jens Axboe [ Upstream commit 4464853277d0ccdb9914608dd1332f0fa2f9846f ] 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 Signed-off-by: Sasha Levin --- io_uring/io_uring.c | 4 ++-- io_uring/io_uring.h | 15 +++++++++++---- io_uring/poll.c | 8 ++++++++ 3 files changed, 21 insertions(+), 6 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 17771cb3c333..71f1cabb9f3d 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 50bc3af44953..4334cd30c423 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" @@ -207,12 +208,18 @@ 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 d9bf1767867e..fded1445a803 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -429,6 +429,14 @@ 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); -- 2.35.1