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 A800AC27C76 for ; Sun, 22 Jan 2023 15:16:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230512AbjAVPQU (ORCPT ); Sun, 22 Jan 2023 10:16:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230511AbjAVPQT (ORCPT ); Sun, 22 Jan 2023 10:16:19 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53FF622038 for ; Sun, 22 Jan 2023 07:16:18 -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 dfw.source.kernel.org (Postfix) with ESMTPS id E3AD660C48 for ; Sun, 22 Jan 2023 15:16:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01DDBC433EF; Sun, 22 Jan 2023 15:16:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1674400577; bh=AeCHHQjwEnJ406A9haBiXqp0zCwTpMkEvbCGhoH5fu0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D3kan2a1OqwfQ/r23R2ZKVJsZhn7VsDb+aefhBXydWH7lGJci4F5bRxJks7wK+8O8 cP7J9qitWclGkp0PlAPp2b9X7qKE+5GdSFQhe8+PuL3gig2mjKT+SCsru47x1cgeR3 FV1dL+UHcdgHZtD0mBqnQLHMW4zMnFkrEMyWqp9U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jens Axboe , Sasha Levin Subject: [PATCH 5.15 028/117] eventpoll: add EPOLL_URING_WAKE poll wakeup flag Date: Sun, 22 Jan 2023 16:03:38 +0100 Message-Id: <20230122150233.875098720@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230122150232.736358800@linuxfoundation.org> References: <20230122150232.736358800@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jens Axboe [ Upstream commit caf1aeaffc3b09649a56769e559333ae2c4f1802 ] We can have dependencies between epoll and io_uring. Consider an epoll context, identified by the epfd file descriptor, and an io_uring file descriptor identified by iofd. If we add iofd to the epfd context, and arm a multishot poll request for epfd with iofd, then the multishot poll request will repeatedly trigger and generate events until terminated by CQ ring overflow. This isn't a desired behavior. Add EPOLL_URING so that io_uring can pass it in as part of the poll wakeup key, and io_uring can check for that to detect a potential recursive invocation. Cc: stable@vger.kernel.org # 6.0 Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/eventpoll.c | 18 ++++++++++-------- include/uapi/linux/eventpoll.h | 6 ++++++ 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index cf326c53db0f..1ec197825544 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -484,7 +484,8 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) */ #ifdef CONFIG_DEBUG_LOCK_ALLOC -static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi) +static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi, + unsigned pollflags) { struct eventpoll *ep_src; unsigned long flags; @@ -515,16 +516,17 @@ static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi) } spin_lock_irqsave_nested(&ep->poll_wait.lock, flags, nests); ep->nests = nests + 1; - wake_up_locked_poll(&ep->poll_wait, EPOLLIN); + wake_up_locked_poll(&ep->poll_wait, EPOLLIN | pollflags); ep->nests = 0; spin_unlock_irqrestore(&ep->poll_wait.lock, flags); } #else -static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi) +static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi, + unsigned pollflags) { - wake_up_poll(&ep->poll_wait, EPOLLIN); + wake_up_poll(&ep->poll_wait, EPOLLIN | pollflags); } #endif @@ -735,7 +737,7 @@ static void ep_free(struct eventpoll *ep) /* We need to release all tasks waiting for these file */ if (waitqueue_active(&ep->poll_wait)) - ep_poll_safewake(ep, NULL); + ep_poll_safewake(ep, NULL, 0); /* * We need to lock this because we could be hit by @@ -1201,7 +1203,7 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v /* We have to call this outside the lock */ if (pwake) - ep_poll_safewake(ep, epi); + ep_poll_safewake(ep, epi, pollflags & EPOLL_URING_WAKE); if (!(epi->event.events & EPOLLEXCLUSIVE)) ewake = 1; @@ -1546,7 +1548,7 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, /* We have to call this outside the lock */ if (pwake) - ep_poll_safewake(ep, NULL); + ep_poll_safewake(ep, NULL, 0); return 0; } @@ -1622,7 +1624,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, /* We have to call this outside the lock */ if (pwake) - ep_poll_safewake(ep, NULL); + ep_poll_safewake(ep, NULL, 0); return 0; } diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h index 8a3432d0f0dc..e687658843b1 100644 --- a/include/uapi/linux/eventpoll.h +++ b/include/uapi/linux/eventpoll.h @@ -41,6 +41,12 @@ #define EPOLLMSG (__force __poll_t)0x00000400 #define EPOLLRDHUP (__force __poll_t)0x00002000 +/* + * Internal flag - wakeup generated by io_uring, used to detect recursion back + * into the io_uring poll handler. + */ +#define EPOLL_URING_WAKE ((__force __poll_t)(1U << 27)) + /* Set exclusive wakeup mode for the target file descriptor */ #define EPOLLEXCLUSIVE ((__force __poll_t)(1U << 28)) -- 2.39.0