From patchwork Sat Oct 28 12:58:24 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 10030993 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8EC756032C for ; Sat, 28 Oct 2017 12:54:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 80C26283C5 for ; Sat, 28 Oct 2017 12:54:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 750FA2842B; Sat, 28 Oct 2017 12:54:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 14297283C5 for ; Sat, 28 Oct 2017 12:54:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751230AbdJ1MyT (ORCPT ); Sat, 28 Oct 2017 08:54:19 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:9467 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751179AbdJ1Mwa (ORCPT ); Sat, 28 Oct 2017 08:52:30 -0400 Received: from 172.30.72.59 (EHLO DGGEMS408-HUB.china.huawei.com) ([172.30.72.59]) by dggrg04-dlp.huawei.com (MOS 4.4.6-GA FastPath queued) with ESMTP id DJY13234; Sat, 28 Oct 2017 20:52:20 +0800 (CST) Received: from huawei.com (10.175.124.28) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.361.1; Sat, 28 Oct 2017 20:52:14 +0800 From: Hou Tao To: CC: , , , , , Subject: [RFC][PATCH 5/8] epoll: iterate epi in file->f_ep_links by using list_first_or_null_rcu Date: Sat, 28 Oct 2017 20:58:24 +0800 Message-ID: <1509195507-29037-6-git-send-email-houtao1@huawei.com> X-Mailer: git-send-email 2.7.5 In-Reply-To: <1509195507-29037-1-git-send-email-houtao1@huawei.com> References: <1509195507-29037-1-git-send-email-houtao1@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.124.28] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090204.59F47D84.008F, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: ccad9611fbed56f66f584ab7a27061a3 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When eventpoll_release_file() iterates epitem in file->f_ep_links, the epitem may be removed by ep_free(). To protect again the concurrent writer, iterate file->f_ep_links by using rcu_read_lock() and list_first_or_null_rcu() Signed-off-by: Hou Tao --- fs/eventpoll.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 18de596..e1e4796 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1033,12 +1033,22 @@ void eventpoll_release_file(struct file *file) * * Besides, ep_remove() acquires the lock, so we can't hold it here. */ - list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { + rcu_read_lock(); + while (true) { + epi = list_first_or_null_rcu(&file->f_ep_links, struct epitem, fllink); + if (!epi) + break; + ep = epi->ep; + rcu_read_unlock(); + mutex_lock_nested(&ep->mtx, 0); ep_remove(ep, epi); mutex_unlock(&ep->mtx); + + rcu_read_lock(); } + rcu_read_unlock(); /* * The file can not been added to tfile_check_list again, because