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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 DE832C169C4 for ; Sun, 3 Feb 2019 12:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A72A32082C for ; Sun, 3 Feb 2019 12:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727868AbfBCMqv (ORCPT ); Sun, 3 Feb 2019 07:46:51 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:3173 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726584AbfBCMqu (ORCPT ); Sun, 3 Feb 2019 07:46:50 -0500 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 91FBB686B6BAC015B0E0; Sun, 3 Feb 2019 20:46:48 +0800 (CST) Received: from [127.0.0.1] (10.57.115.182) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.408.0; Sun, 3 Feb 2019 20:46:40 +0800 Subject: Re: [PATCH V2 rdma-next 2/3] RDMA/hns: Fix the chip hanging caused by sending mailbox&CMQ during reset To: Jason Gunthorpe References: <1547868967-115951-1-git-send-email-xavier.huwei@huawei.com> <1547868967-115951-3-git-send-email-xavier.huwei@huawei.com> <20190123224041.GA11605@ziepe.ca> <5C492D59.8030707@huawei.com> <20190124183120.GD17167@ziepe.ca> <5C4A714C.2070109@huawei.com> <20190125215018.GF23001@ziepe.ca> <5C4BBC3E.2000004@huawei.com> <20190128182759.GA25106@ziepe.ca> <5C4FB800.3060506@huawei.com> <20190129034505.GK25106@ziepe.ca> CC: , , , , , , , From: "Wei Hu (Xavier)" Message-ID: <5C56E2B0.9060303@huawei.com> Date: Sun, 3 Feb 2019 20:46:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20190129034505.GK25106@ziepe.ca> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.57.115.182] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/1/29 11:45, Jason Gunthorpe wrote: > On Tue, Jan 29, 2019 at 10:18:40AM +0800, Wei Hu (Xavier) wrote: >> >> On 2019/1/29 2:27, Jason Gunthorpe wrote: >>> On Sat, Jan 26, 2019 at 09:47:42AM +0800, Wei Hu (Xavier) wrote: >>>> On 2019/1/26 5:50, Jason Gunthorpe wrote: >>>>> On Fri, Jan 25, 2019 at 10:15:40AM +0800, Wei Hu (Xavier) wrote: >>>>>> On 2019/1/25 2:31, Jason Gunthorpe wrote: >>>>>>> On Thu, Jan 24, 2019 at 11:13:29AM +0800, Wei Hu (Xavier) wrote: >>>>>>>> On 2019/1/24 6:40, Jason Gunthorpe wrote: >>>>>>>>> On Sat, Jan 19, 2019 at 11:36:06AM +0800, Wei Hu (Xavier) wrote: >>>>>>>>> >>>>>>>>>> +static int hns_roce_v2_cmd_hw_resetting(struct hns_roce_dev *hr_dev, >>>>>>>>>> + unsigned long instance_stage, >>>>>>>>>> + unsigned long reset_stage) >>>>>>>>>> +{ >>>>>>>>>> + struct hns_roce_v2_priv *priv = (struct hns_roce_v2_priv *)hr_dev->priv; >>>>>>>>>> + struct hnae3_handle *handle = priv->handle; >>>>>>>>>> + const struct hnae3_ae_ops *ops = handle->ae_algo->ops; >>>>>>>>>> + unsigned long end; >>>>>>>>>> + >>>>>>>>>> + /* When hardware reset is detected, we should stop sending mailbox&cmq >>>>>>>>>> + * to hardware, and wait until hardware reset finished. If now >>>>>>>>>> + * in .init_instance() function, we should exit with error. If now at >>>>>>>>>> + * HNAE3_INIT_CLIENT stage of soft reset process, we should exit with >>>>>>>>>> + * error, and then HNAE3_INIT_CLIENT related process can rollback the >>>>>>>>>> + * operation like notifing hardware to free resources, HNAE3_INIT_CLIENT >>>>>>>>>> + * related process will exit with error to notify NIC driver to >>>>>>>>>> + * reschedule soft reset process once again. >>>>>>>>>> + */ >>>>>>>>>> + end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies; >>>>>>>>>> + while (ops->get_hw_reset_stat(handle) && time_before(jiffies, end)) >>>>>>>>>> + udelay(1); >>>>>>>>> I thought you were getting rid of these loops? >>>>>>>> Hi, Jason >>>>>>>> >>>>>>>> Upper applications maybe notify driver to issue mailbox or CMD >>>>>>>> commands to hardware, some commands used to cancel resources, >>>>>>>> destory bt/destory cq/unreg mr/destory qp etc. when such >>>>>>>> commands are executed successfully, the hardware engine will >>>>>>>> no longer access some memory registered by the driver. >>>>>>>> >>>>>>>> When reset occurs, it is possible for upper applications notify driver >>>>>>>> to issue mailbox or CMD commands, we need to wait until hardware >>>>>>>> reset finished to ensure that hardware no longer accesses related >>>>>>>> memory. >>>>>>> You should not wait for things using loops like the above. >>>>>> Hi, Jason >>>>>> >>>>>> Are your comments foucsing on udelay? If not, thanks for your detail >>>>>> information. >>>>>> In hns3 RoCE driver, some CMQ/mailbox operation are called inside >>>>>> the lock, >>>>>> we can't use msleep in the lock, otherwise it will cause deadlock. >>>>>> When reset occurs, RDMA service cannot be provided normally, I think >>>>>> in this >>>>>> case using udelay will not have a great impact. >>>>> You should not use any kind of sleep call in a loop like this. >>>> Hi, Jason >>>> >>>> OK, I got your opinion and will modify it in v3 patch as below: >>>> >>>> end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies; >>>> while (time_before(jiffies, end)) >>>> if (!ops->get_hw_reset_stat(handle)) >>>> break; >>> You shouldn't be looping like this at all, a busy loop is worse, don't >>> try and open code spinlocks. >> Hi, Jason >> >> OK, we will modify some places calling CMQ/mailbox operation, >> replace spinlock with mutex, and add msleep here: >> >> end = msecs_to_jiffies(HNS_ROCE_V2_HW_RST_TIMEOUT) + jiffies; >> while (time_before(jiffies, end)) { >> if (!ops->get_hw_reset_stat(handle)) >> break; >> msleep(20); >> } > How many more times do I have to say not to code spin loops like > this???? Use proper locking! Hi, Jason Ok, Thanks for your comments. And we removed the loop operation here and sent patch v4. Thanks Regards Xavier > Jason > > . >