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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 053E6C31E40 for ; Fri, 9 Aug 2019 17:30:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8A98214C6 for ; Fri, 9 Aug 2019 17:30:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726219AbfHIRa6 (ORCPT ); Fri, 9 Aug 2019 13:30:58 -0400 Received: from mga05.intel.com ([192.55.52.43]:64925 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726157AbfHIRa5 (ORCPT ); Fri, 9 Aug 2019 13:30:57 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Aug 2019 10:30:56 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,366,1559545200"; d="scan'208";a="186726085" Received: from linux.intel.com ([10.54.29.200]) by orsmga002.jf.intel.com with ESMTP; 09 Aug 2019 10:30:56 -0700 Received: from [10.54.74.33] (skuppusw-desk.jf.intel.com [10.54.74.33]) by linux.intel.com (Postfix) with ESMTP id 65B2D580417; Fri, 9 Aug 2019 10:30:56 -0700 (PDT) Reply-To: sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH] PCI: pciehp: Avoid returning prematurely from sysfs requests To: Lukas Wunner , Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Xiongfeng Wang References: <4174210466e27eb7e2243dd1d801d5f75baaffd8.1565345211.git.lukas@wunner.de> From: sathyanarayanan kuppuswamy Organization: Intel Message-ID: Date: Fri, 9 Aug 2019 10:28:15 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <4174210466e27eb7e2243dd1d801d5f75baaffd8.1565345211.git.lukas@wunner.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hi, On 8/9/19 3:28 AM, Lukas Wunner wrote: > A sysfs request to enable or disable a PCIe hotplug slot should not > return before it has been carried out. That is sought to be achieved > by waiting until the controller's "pending_events" have been cleared. > > However the IRQ thread pciehp_ist() clears the "pending_events" before > it acts on them. If pciehp_sysfs_enable_slot() / _disable_slot() happen > to check the "pending_events" after they have been cleared but while > pciehp_ist() is still running, the functions may return prematurely > with an incorrect return value. Can this be fixed by changing the sequence of clearing the pending_events in pciehp_ist() ? > > Fix by introducing an "ist_running" flag which must be false before a > sysfs request is allowed to return. > > Fixes: 32a8cef274fe ("PCI: pciehp: Enable/disable exclusively from IRQ thread") > Link: https://lore.kernel.org/linux-pci/1562226638-54134-1-git-send-email-wangxiongfeng2@huawei.com > Reported-and-tested-by: Xiongfeng Wang > Signed-off-by: Lukas Wunner > Cc: stable@vger.kernel.org # v4.19+ > --- > drivers/pci/hotplug/pciehp.h | 2 ++ > drivers/pci/hotplug/pciehp_ctrl.c | 6 ++++-- > drivers/pci/hotplug/pciehp_hpc.c | 2 ++ > 3 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h > index 8c51a04b8083..e316bde45c7b 100644 > --- a/drivers/pci/hotplug/pciehp.h > +++ b/drivers/pci/hotplug/pciehp.h > @@ -72,6 +72,7 @@ extern int pciehp_poll_time; > * @reset_lock: prevents access to the Data Link Layer Link Active bit in the > * Link Status register and to the Presence Detect State bit in the Slot > * Status register during a slot reset which may cause them to flap > + * @ist_running: flag to keep user request waiting while IRQ thread is running > * @request_result: result of last user request submitted to the IRQ thread > * @requester: wait queue to wake up on completion of user request, > * used for synchronous slot enable/disable request via sysfs > @@ -101,6 +102,7 @@ struct controller { > > struct hotplug_slot hotplug_slot; /* hotplug core interface */ > struct rw_semaphore reset_lock; > + unsigned int ist_running; > int request_result; > wait_queue_head_t requester; > }; > diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c > index 631ced0ab28a..1ce9ce335291 100644 > --- a/drivers/pci/hotplug/pciehp_ctrl.c > +++ b/drivers/pci/hotplug/pciehp_ctrl.c > @@ -368,7 +368,8 @@ int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot) > ctrl->request_result = -ENODEV; > pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC); > wait_event(ctrl->requester, > - !atomic_read(&ctrl->pending_events)); > + !atomic_read(&ctrl->pending_events) && > + !ctrl->ist_running); > return ctrl->request_result; > case POWERON_STATE: > ctrl_info(ctrl, "Slot(%s): Already in powering on state\n", > @@ -401,7 +402,8 @@ int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot) > mutex_unlock(&ctrl->state_lock); > pciehp_request(ctrl, DISABLE_SLOT); > wait_event(ctrl->requester, > - !atomic_read(&ctrl->pending_events)); > + !atomic_read(&ctrl->pending_events) && > + !ctrl->ist_running); > return ctrl->request_result; > case POWEROFF_STATE: > ctrl_info(ctrl, "Slot(%s): Already in powering off state\n", > diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c > index bd990e3371e3..9e2d7688e8cc 100644 > --- a/drivers/pci/hotplug/pciehp_hpc.c > +++ b/drivers/pci/hotplug/pciehp_hpc.c > @@ -608,6 +608,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id) > irqreturn_t ret; > u32 events; > > + ctrl->ist_running = true; > pci_config_pm_runtime_get(pdev); > > /* rerun pciehp_isr() if the port was inaccessible on interrupt */ > @@ -654,6 +655,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id) > up_read(&ctrl->reset_lock); > > pci_config_pm_runtime_put(pdev); > + ctrl->ist_running = false; > wake_up(&ctrl->requester); > return IRQ_HANDLED; > } -- Sathyanarayanan Kuppuswamy Linux kernel developer