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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 85CD3C433DF for ; Fri, 26 Jun 2020 15:10:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 655AD206E9 for ; Fri, 26 Jun 2020 15:10:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernelim-com.20150623.gappssmtp.com header.i=@kernelim-com.20150623.gappssmtp.com header.b="fpxsguBU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728285AbgFZPK6 (ORCPT ); Fri, 26 Jun 2020 11:10:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728283AbgFZPK6 (ORCPT ); Fri, 26 Jun 2020 11:10:58 -0400 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC77CC03E97A for ; Fri, 26 Jun 2020 08:10:57 -0700 (PDT) Received: by mail-ej1-x641.google.com with SMTP id i14so9713034ejr.9 for ; Fri, 26 Jun 2020 08:10:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernelim-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=JtRyGt6tiuqtwS1yKOlAkCyE7jiftgXfal15sd+NZdk=; b=fpxsguBU3JER73RU9qOPNpFE2E2jEx1fk2c9+73s4rDH2TAlUCBSI3cTmdvV9GnNe9 IlQAHwtLYEN9UJE4ukGlACk7K+CSBKOVBq6taeWa2FKfHlMBRaNttWyz/HHeMreB7J3+ OdR1QGL7LYABeAivxYYb+8dj8bApe1g2IgTYySdh7SQZIwZ6G+1eHJGaeKDv3Q7z9kHK 8xUNgZtoQ8GTEQcEoqida/heTNf2Iku4SUSSDBWUjgZ9CnVpTDidL7R3GZShau5UHQFt V5B/IJQvFZjP3PVeDThT0ZLLXCDRQq3/kVcZcONjJ2EzHgl38QrdqSGWztmMcqR6RfAc NhMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=JtRyGt6tiuqtwS1yKOlAkCyE7jiftgXfal15sd+NZdk=; b=qKl0whZEQadxPmiT8cw7FA9E/bXTXMbVGguGGQwQFmtjo1wEbEhl0BP9ip+KMOb9ml uXXMXnSpCPTkK7F1v3HqvEQWkrPWfpdoGFOOzk+phB+BHvoYkTjZ4eEP1niuYdLr6Id5 ftG1rby6Px04vMQhtPXz3fKcdQiV/2eu73w4cMIz/vvnxtVSYdWHO+V25JFvy398uFmd fR5qxoq4viIIr0YjLAow/JLos7FTG6oHBIx0o3wiw5FeTZ+Usv/Z3+eP2IWODL9VUipF 1s60Ao9QpgXkkMS7rIyFuCiDJI/WvlsAZEqSHkiXGm9qxhzNAHSlCAoD2con50v8aIPO vbKQ== X-Gm-Message-State: AOAM533JntHoxmtTQvMQgE6s0WYTPspTKibYSYxW8Blwb1f49IpLKhrR sJd9WyvMp2UzuDmhGSH/9d2g7A== X-Google-Smtp-Source: ABdhPJzMuNuTrIAqicq/H7KVkcSv7BRHCGUNaCzEKApDBeNuY7YWlK/xalMxHcPVhN9SOma6pEM/QA== X-Received: by 2002:a17:906:4a87:: with SMTP id x7mr2530833eju.44.1593184256489; Fri, 26 Jun 2020 08:10:56 -0700 (PDT) Received: from gmail.com ([141.226.169.176]) by smtp.gmail.com with ESMTPSA id m23sm2760801ejc.38.2020.06.26.08.10.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2020 08:10:55 -0700 (PDT) Date: Fri, 26 Jun 2020 18:10:52 +0300 From: Dan Aloni To: Chuck Lever Cc: linux-rdma@vger.kernel.org, Linux NFS Mailing List Subject: Re: [PATCH] xprtrdma: fix EP destruction logic Message-ID: <20200626151052.6cckaquyu7k3nd6b@gmail.com> References: <0E2AA9D9-2503-462C-952D-FC0DD5111BD1@oracle.com> <20200626071034.34805-1-dan@kernelim.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Fri, Jun 26, 2020 at 08:56:41AM -0400, Chuck Lever wrote: > > On Jun 26, 2020, at 3:10 AM, Dan Aloni wrote: [..] > > - Add a mutex in `rpcrdma_ep_destroy` to guard against concurrent calls > > to `rpcrdma_xprt_disconnect` coming from either `rpcrdma_xprt_connect` > > or `xprt_rdma_close`. > > NAK. The RPC client provides appropriate exclusion, please let's not > add more serialization that can introduce further deadlocks. It appeared to me that this exclusion does not works well. As for my considerations, if I am not mistaken from analyzing crashes I've seen: -> xprt_autoclose (running on xprtiod) -> xprt->ops->close -> xprt_rdma_close -> rpcrdma_xprt_disconnect and: -> xprt_rdma_connect_worker (running on xprtiod) -> rpcrdma_xprt_connect -> rpcrdma_xprt_disconnect I understand the rationale or at least the aim that `close` and `connect` ops should not be concurrent on the same `xprt`, however: * `xprt_force_disconnect`, is called from various places, queues a call to `xprt_autoclose` to the background on `xprtiod` workqueue item, conditioned that `!XPRT_LOCKED` which is the case for connect that went to the background. * `xprt_rdma_connect` also sends `xprt_rdma_connect_worker` as an `xprtiod` workqueue item, unconditionally. So we have two work items that can run in parallel, and I don't see clear gating on this from the code. Maybe there's a simpler fix for this. Perhaps a `cancel_delayed_work_sync(&r_xprt->rx_connect_worker);` is appropriate in `xprt_rdma_close`? -- Dan Aloni