From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH V2 rdma-next 2/3] RDMA/hns: Fix the chip hanging caused by sending mailbox&CMQ during reset Date: Fri, 25 Jan 2019 14:50:18 -0700 Message-ID: <20190125215018.GF23001@ziepe.ca> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <5C4A714C.2070109@huawei.com> Sender: linux-kernel-owner@vger.kernel.org To: "Wei Hu (Xavier)" Cc: dledford@redhat.com, linux-rdma@vger.kernel.org, lijun_nudt@163.com, oulijun@huawei.com, liudongdong3@huawei.com, linuxarm@huawei.com, linux-kernel@vger.kernel.org, xavier_huwei@163.com List-Id: linux-rdma@vger.kernel.org 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. Jason