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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 227A2C432C1 for ; Tue, 24 Sep 2019 03:54:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1FDA206C2 for ; Tue, 24 Sep 2019 03:54:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438439AbfIXDys (ORCPT ); Mon, 23 Sep 2019 23:54:48 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:38254 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389841AbfIXDys (ORCPT ); Mon, 23 Sep 2019 23:54:48 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 81C1FF67A270345BBA2F; Tue, 24 Sep 2019 11:54:46 +0800 (CST) Received: from [127.0.0.1] (10.74.223.196) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Tue, 24 Sep 2019 11:54:38 +0800 Subject: Re: [PATCH for-next] RDMA/hns: Bugfix for flush cqe in case softirq and multi-process To: Leon Romanovsky CC: , , , References: <1567686671-4331-1-git-send-email-liweihang@hisilicon.com> <20190908080303.GC26697@unreal> <20190910075216.GX6601@unreal> <94ad1f56-afc6-ec78-4aa2-85d03c644031@huawei.com> <0d4ce391-6619-783d-55a8-fa2524af7b9c@huawei.com> <20190923050125.GK14368@unreal> From: "Liuyixian (Eason)" Message-ID: <1224a3a0-50fb-dd6a-f22e-833e74ec77c3@huawei.com> Date: Tue, 24 Sep 2019 11:54:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20190923050125.GK14368@unreal> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.74.223.196] X-CFilter-Loop: Reflected Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 2019/9/23 13:01, Leon Romanovsky wrote: > On Fri, Sep 20, 2019 at 11:55:56AM +0800, Liuyixian (Eason) wrote: >> >> >> On 2019/9/11 21:17, Liuyixian (Eason) wrote: >>> >>> >>> On 2019/9/10 15:52, Leon Romanovsky wrote: >>>> On Tue, Sep 10, 2019 at 02:40:20PM +0800, Liuyixian (Eason) wrote: >>>>> >>>>> >>>>> On 2019/9/8 16:03, Leon Romanovsky wrote: >>>>>> On Thu, Sep 05, 2019 at 08:31:11PM +0800, Weihang Li wrote: >>>>>>> From: Yixian Liu >>>>>>> >>>>>>> Hip08 has the feature flush cqe, which help to flush wqe in workqueue >>>>>>> (sq and rq) when error happened by transmitting producer index with >>>>>>> mailbox to hardware. Flush cqe is emplemented in post send and recv >>>>>>> verbs. However, under NVMe cases, these verbs will be called under >>>>>>> softirq context, and it will lead to following calltrace with >>>>>>> current driver as mailbox used by flush cqe can go to sleep. >>>>>>> >>>>>>> This patch solves this problem by using workqueue to do flush cqe, >>>>>> >>>>>> Unbelievable, almost every bug in this driver is solved by introducing >>>>>> workqueue. You should fix "sleep in flush path" issue and not by adding >>>>>> new workqueue. >>>>>> >>>>> Hi Leon, >>>>> >>>>> Thanks for the comment. >>>>> Up to now, for hip08, only one place use workqueue in hns_roce_hw_v2.c >>>>> where for irq prints. >>>> >>>> Thanks to our lack of desire to add more workqueues and previous patches >>>> which removed extra workqueues from the driver. >>>> >>> Thanks, I see. >>> >>>>> >>>>> The solution for flush cqe in this patch is as follow: >>>>> While flush cqe should be implement, the driver should modify qp to error state >>>>> through mailbox with the newest product index of sq and rq, the hardware then >>>>> can flush all outstanding wqes in sq and rq. >>>>> >>>>> That's the whole mechanism of flush cqe, also is the flush path. We can't >>>>> change neither mailbox sleep attribute or flush cqe occurred in post send/recv. >>>>> To avoid the calltrace of flush cqe in post verbs under NVMe softirq, >>>>> use workqueue for flush cqe seems reasonable. >>>>> >>>>> As far as I know, there is no other alternative solution for this situation. >>>>> I will be very grateful if you reminder me more information. >>>> >>>> ib_drain_rq/ib_drain_sq/ib_drain_qp???? >>>> >>> Hi Leon, >>> >>> I think these interfaces are designed for application to check that all wqes >>> have been processed by hardware, so called drain or flush. However, it is not >>> the same as the flush in this patch. The solution in this patch is used >>> to help the hardware generate flush cqes for outstanding wqes while qp error. >>> >> Hi Leon, >> >> What's your opinion about above? Do you have any further comments? > > My opinion didn't change, you need to read discussions about ib_drain_*() > functions, how and why they were introduced. It is a way to go. > > Thanks Hi Leon, Thanks a lot! I will dig those functions for my problem. > >> >> Thanks. >> >>>>> >>>>> Thanks >>>>> >>>>>> _______________________________________________ >>>>>> Linuxarm mailing list >>>>>> Linuxarm@huawei.com >>>>>> http://hulk.huawei.com/mailman/listinfo/linuxarm >>>>>> >>>>>> >>>>> >>>> >>>> . >>>> >>> >>> _______________________________________________ >>> Linuxarm mailing list >>> Linuxarm@huawei.com >>> http://hulk.huawei.com/mailman/listinfo/linuxarm >>> >>> . >>> >> > > . >