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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id w88sm71587926pfk.11.2019.01.28.10.28.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 28 Jan 2019 10:28:00 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1goBdX-0007vz-RM; Mon, 28 Jan 2019 11:27:59 -0700 Date: Mon, 28 Jan 2019 11:27:59 -0700 From: Jason Gunthorpe 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 Subject: Re: [PATCH V2 rdma-next 2/3] RDMA/hns: Fix the chip hanging caused by sending mailbox&CMQ during reset Message-ID: <20190128182759.GA25106@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> <20190125215018.GF23001@ziepe.ca> <5C4BBC3E.2000004@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5C4BBC3E.2000004@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Jason