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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 4F05DC433FE for ; Fri, 11 Dec 2020 06:52:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0447723F2C for ; Fri, 11 Dec 2020 06:52:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436524AbgLKGva (ORCPT ); Fri, 11 Dec 2020 01:51:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2395567AbgLKGvG (ORCPT ); Fri, 11 Dec 2020 01:51:06 -0500 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 327EBC0613D6 for ; Thu, 10 Dec 2020 22:50:26 -0800 (PST) Received: by mail-ej1-x642.google.com with SMTP id f23so10895758ejk.2 for ; Thu, 10 Dec 2020 22:50:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloud.ionos.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=qOyH91HYE+ecPMqr9RDNeOMk/juwGLFp3UZjYGKos0Y=; b=Ceqw4olq/sAJC8ut4FwudzBPTgTLzdSg1R0elmKcY4TQTJVvz6ATPUvSrpGIxs+n47 ggA+/7oKp1P+G2/j2gnknwjocNnCaVCvzSuanlGhMgCVTFbeCXqHvii0J+WV623XuVGh lmLG/66N7kjOyw60lXpGkU7aiPvx/JIM0yeC17Q5jjX+roK/8h/fyRXvM22ZuritV+af ju8IlBrgn6V6q85USRimr7F8ITP9nQWn+aoTR30wc55BSIVebTcv0pJbUbzLnOIa/iX7 aSm0uIzT+Dg0VYA8PtlUW4b2T7+//HvmxGEO9oDOpB0Ek0pvRbvtLCXxPKy5TrC4cvJW oi0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=qOyH91HYE+ecPMqr9RDNeOMk/juwGLFp3UZjYGKos0Y=; b=C7X6XlagccmVVkGohwmrJ2EyA1uKUsbm5VGflfdZgO/MR8ZSg5yotU7DRc0+SdBjo3 uapdy1jrRVoeDF92M5hNRSmUtVCr84eOMKJ8ODlipx9wgnHp712p/Y92E0mlcxTEvK5k XhO7MsHXSFuJx/WNDUlPOm/p/Xccn2V9WPhAUI6Q/I9xu4Yt780gbR+4QIHGxOs4ak73 WN5zSB8wbbzO2SNIQzhjSwS7IIo283i/+EagGsPCK86gJsQIgedfdqPykTLizpr5ELxB O0bxyts2jF4myGyYr8GzVke0+mUUvQ34Gykhau3/lm0kGuUWh3y4t+JOGkp+tXzlMk24 1FgA== X-Gm-Message-State: AOAM531tN/ja/zfr5Nkj/7tAm/wQajfr58X6SFKPb7mXQXCTItnXHGho XmUJx7+2qHvNzeikGNKdIQ4bocM5Re/6zicNLZm27w== X-Google-Smtp-Source: ABdhPJzwzI3I0JFYELFCEqzjr7jszBkX0BG0k3qz6ObZMpxeSdLACYTmE5uEb/7LTxPC3oUmZsuCDllSJ9bCrWgNtaE= X-Received: by 2002:a17:906:16da:: with SMTP id t26mr9404230ejd.478.1607669424958; Thu, 10 Dec 2020 22:50:24 -0800 (PST) MIME-Version: 1.0 References: <20201209164542.61387-1-jinpu.wang@cloud.ionos.com> <20201209164542.61387-3-jinpu.wang@cloud.ionos.com> In-Reply-To: From: Jinpu Wang Date: Fri, 11 Dec 2020 07:50:13 +0100 Message-ID: Subject: Re: [PATCH for-next 02/18] RMDA/rtrs-srv: Occasionally flush ongoing session closing To: Guoqing Jiang Cc: linux-rdma@vger.kernel.org, Bart Van Assche , Leon Romanovsky , Doug Ledford , Jason Gunthorpe , Danil Kipnis Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Fri, Dec 11, 2020 at 3:35 AM Guoqing Jiang wrote: > > > > On 12/10/20 15:56, Jinpu Wang wrote: > > On Wed, Dec 9, 2020 at 5:45 PM Jack Wang wrote: > >> > >> If there are many establishments/teardowns, we need to make sure > >> we do not consume too much system memory. Thus let on going > >> session closing to finish before accepting new connection. > >> > >> Inspired by commit 777dc82395de ("nvmet-rdma: occasionally flush ongoing controller teardown") > >> Signed-off-by: Jack Wang > >> Reviewed-by: Guoqing Jiang > > Please ignore this one, it could lead to deadlock, due to the fact > > cma_ib_req_handler is holding > > mutex_lock(&listen_id->handler_mutex) when calling into > > rtrs_rdma_connect, we call close_work which will call rdma_destroy_id, > > which > > could try to hold the same handler_mutex, so deadlock. > > > > I am wondering if nvmet-rdma has the similar issue or not, if so, maybe > introduce a locked version of rdma_destroy_id. > > Thanks, > Guoqing No, I was wrong. I rechecked the code, it's not a valid deadlock, in cma_ib_req_handler, the conn_id is newly created in https://elixir.bootlin.com/linux/latest/source/drivers/infiniband/core/cma.c#L2185. Flush_workqueue will only flush close_work for any other cm_id, but not the newly created one conn_id, it has not associated with anything yet. The same applies to nvme-rdma. so it's a false alarm by lockdep. Regards! Jack