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 30060C433EF for ; Fri, 1 Apr 2022 03:23:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244495AbiDADY7 (ORCPT ); Thu, 31 Mar 2022 23:24:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244491AbiDADY4 (ORCPT ); Thu, 31 Mar 2022 23:24:56 -0400 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8B8425E32B for ; Thu, 31 Mar 2022 20:23:07 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=yaohongbo@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0V8mkkFC_1648783383; Received: from 30.225.24.82(mailfrom:yaohongbo@linux.alibaba.com fp:SMTPD_---0V8mkkFC_1648783383) by smtp.aliyun-inc.com(127.0.0.1); Fri, 01 Apr 2022 11:23:04 +0800 Message-ID: Date: Fri, 1 Apr 2022 11:23:01 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH RESEND] uio/uio_pci_generic: Introduce refcnt on open/release To: "Michael S. Tsirkin" Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, alikernel-developer@linux.alibaba.com, gang.cao@intel.com, shouqu.ssq@alibaba-inc.com, yangxiu.yx@alibaba-inc.com References: <1648693432-129409-1-git-send-email-yaohongbo@linux.alibaba.com> <20220331162952-mutt-send-email-mst@kernel.org> From: Yao Hongbo In-Reply-To: <20220331162952-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org + cc. 在 2022/4/1 上午4:30, Michael S. Tsirkin 写道: > On Thu, Mar 31, 2022 at 10:23:52AM +0800, Yao Hongbo wrote: >> If two userspace programs both open the PCI UIO fd, when one >> of the program exits uncleanly, the other will cause IO hang >> due to bus-mastering disabled. > > With two programs poking at the same device, how is this ever > supposed to work even while both are alive? > >> It's a common usage for spdk/dpdk to use UIO. So, introduce refcnt >> to avoid such problems. >> >> Fixes: 865a11f("uio/uio_pci_generic: Disable bus-mastering on release") >> Reported-by: Xiu Yang >> Signed-off-by: Yao Hongbo >> --- >> drivers/uio/uio_pci_generic.c | 16 +++++++++++++++- >> 1 file changed, 15 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c >> index e03f9b5..8add2cf 100644 >> --- a/drivers/uio/uio_pci_generic.c >> +++ b/drivers/uio/uio_pci_generic.c >> @@ -31,6 +31,7 @@ >> struct uio_pci_generic_dev { >> struct uio_info info; >> struct pci_dev *pdev; >> + atomic_t refcnt; >> }; >> >> static inline struct uio_pci_generic_dev * >> @@ -39,6 +40,14 @@ struct uio_pci_generic_dev { >> return container_of(info, struct uio_pci_generic_dev, info); >> } >> >> +static int open(struct uio_info *info, struct inode *inode) >> +{ >> + struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info); >> + >> + atomic_inc(&gdev->refcnt); >> + return 0; >> +} >> + >> static int release(struct uio_info *info, struct inode *inode) >> { >> struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info); >> @@ -51,7 +60,9 @@ static int release(struct uio_info *info, struct inode *inode) >>  * Note that there's a non-zero chance doing this will wedge the device >>  * at least until reset. >> */ >> - pci_clear_master(gdev->pdev); >> + if (atomic_dec_and_test(&gdev->refcnt)) >> + pci_clear_master(gdev->pdev); >> + >> return 0; >> } >> >> @@ -92,8 +103,11 @@ static int probe(struct pci_dev *pdev, >> >> gdev->info.name = "uio_pci_generic"; >> gdev->info.version = DRIVER_VERSION; >> + gdev->info.open = open; >> gdev->info.release = release; >> gdev->pdev = pdev; >> + atomic_set(&gdev->refcnt, 0); >> + >> if (pdev->irq && (pdev->irq != IRQ_NOTCONNECTED)) { >> gdev->info.irq = pdev->irq; >> gdev->info.irq_flags = IRQF_SHARED; >> -- >> 1.8.3.1