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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5678C77B70 for ; Fri, 14 Apr 2023 03:41:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229612AbjDNDlU (ORCPT ); Thu, 13 Apr 2023 23:41:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229540AbjDNDkr (ORCPT ); Thu, 13 Apr 2023 23:40:47 -0400 Received: from out-18.mta0.migadu.com (out-18.mta0.migadu.com [IPv6:2001:41d0:1004:224b::12]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9185449F5 for ; Thu, 13 Apr 2023 20:40:43 -0700 (PDT) Message-ID: <230b310a-26ef-34f1-4c3b-c2360088ce04@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1681443640; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W9bW0zXOdOvJDmsTubWdBZzJB+s+MAqkuEXByAddXCg=; b=vPCE9SWC22zDhK6VkGzGIi5qxo+uPsqcBEGiAiYRs2UNHolmGGYdT03CwSYPDj6WaMAQUR 1mK2wZKgFSKJzW3M8HCIvqm5HE/7m+aGlsUrt8o6Ev0WV8mpzzFJiQzYlVEQHVlAF/xEoj 0ZeC1D+4JccfckKUuckT1a8tgMAYksE= Date: Fri, 14 Apr 2023 11:40:35 +0800 MIME-Version: 1.0 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Guoqing Jiang Subject: Re: [PATCH for-next 2/3] RDMA/rtrs: Fix rxe_dealloc_pd warning To: "Zhijian Li (Fujitsu)" , Leon Romanovsky Cc: "haris.iqbal@ionos.com" , "jinpu.wang@ionos.com" , "jgg@ziepe.ca" , "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <1681108984-2-1-git-send-email-lizhijian@fujitsu.com> <1681108984-2-3-git-send-email-lizhijian@fujitsu.com> <20230410120809.GN182481@unreal> <0d9c57db-bca3-adb4-71fd-7362e4842917@linux.dev> <85323eb2-cfc7-d1b8-3a75-3fa63dde29db@fujitsu.com> <20230411122651.GV182481@unreal> <8fe62e38-e43d-3d6c-624f-1c8ce5859788@linux.dev> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/13/23 16:12, Zhijian Li (Fujitsu) wrote: > On 13/04/2023 15:35, Guoqing Jiang wrote: >> Hi, >> >> I take a closer look today. >> >> On 4/12/23 09:15, Zhijian Li (Fujitsu) wrote: >>> On 11/04/2023 20:26, Leon Romanovsky wrote: >>>> On Tue, Apr 11, 2023 at 02:43:46AM +0000, Zhijian Li (Fujitsu) wrote: >>>>> On 10/04/2023 21:10, Guoqing Jiang wrote: >>>>>> On 4/10/23 20:08, Leon Romanovsky wrote: >>>>>>> On Mon, Apr 10, 2023 at 06:43:03AM +0000, Li Zhijian wrote: >>>>>>>> The warning occurs when destroying PD whose reference count is not zero. >>>>>>>> >>>>>>>> Precodition: clt_path->s.con_num is 2. >>>>>>>> So 2 cm connection will be created as below: >>>>>>>> CPU0                                              CPU1 >>>>>>>> init_conns {                              | >>>>>>>>      create_cm() // a. con[0] created        | >>>>>>>>                                              |  a'. rtrs_clt_rdma_cm_handler() { >>>>>>>>                                              |    rtrs_rdma_addr_resolved() >>>>>>>>                                              |      create_con_cq_qp(con); << con[0] >>>>>>>>                                              |  } >>>>>>>>                                              | in this moment, refcnt of PD was increased to 2+ >> What do you mean "refcnt of PD"? usecnt in struct ib_pd or dev_ref. > I mean usecnt in struct ib_pd > > > >>>>>>>>                                              | >>>>>>>>      create_cm() // b. cid = 1, failed       | >>>>>>>>        destroy_con_cq_qp()                   | >>>>>>>>          rtrs_ib_dev_put()                   | >>>>>>>>            dev_free()                        | >>>>>>>>              ib_dealloc_pd(dev->ib_pd) << PD | >>>>>>>>               is destroyed, but refcnt is    | >>>>>>>>               still greater than 0           | >> Assuming you mean "pd->usecnt". We only allocate pd in con[0] by rtrs_ib_dev_find_or_add, >> if con[1] failed to create cm, then alloc_path_reqs -> ib_alloc_mr -> atomic_inc(&pd->usecnt) The above can't be invoked, right? >> can't be triggered. Is there other places could increase the refcnt? > Yes, when create a qp, it will also associate to this PD, that also mean refcnt of PD will be increased. > > When con[0](create_con_cq_qp) succeeded, refcnt of PD will be 2. and then when con[1] failed, since > QP didn't create, refcnt of PD is still 2. con[1]'s cleanup will destroy the PD(ib_dealloc_pd) since dev_ref = 1, after that its > refcnt is still 1. I can see the path increase usecnt to 1. rtrs_cq_qp_create -> create_qp                     -> rdma_create_qp                         -> ib_create_qp                             -> create_qp                             -> ib_qp_usecnt_inc which increases pd->usecnt Where is another place to increase usecnt to 2? >> Then what is the appropriate time to call destroy_con_cq_qp for this scenario? >> Otherwise there could be memory leak. > we must ensure QP in con[0] is closed before destroying the PD. > Currently destroy_con_cq_qp() subroutine will close the opened QP first. Let me try another way, with below change, rtrs_ib_dev_put can't be called from destroy_con_cq_qp, right? + if (!con->has_dev) + return; if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) { rtrs_ib_dev_put(clt_path->s.dev); clt_path->s.dev = NULL; Then when will you dealloc pd and free rtrs_ib_dev? Thanks, Guoqing