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=-5.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 E5D73C433E9 for ; Thu, 18 Mar 2021 19:16:34 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6CCCC64F01 for ; Thu, 18 Mar 2021 19:16:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CCCC64F01 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=bva5eJE74oQlpsdNGitg/gOMQcAH73HHfrIJzWxsN2s=; b=qRORNIbkgWvvgkmbBO0SmFu0S syrVZCfTm2VyaN7uSJ3qlaoaCEv7PbDqKndPGLf5DByTmlxcVwEDmPseAn/2TiYPq7rLt7tNPqk32 eNa329m3IQ3fYYUuFAhrdC/vVwk20YCVGDOLx03IxdfEuIocwqscaSODC11MEo23EsfNzWsEOcl7b HkbixAIuTtB44r0vTfEGdG0vX7xGL01AqVjaYs3FIlbEJMriPCLhqdlOYnHZedg6Gs4EmKbI3ROMj k4gfQsAfNerzksBxvqj/7MS2kMHbZ8TQ+rtWBjd7e2fAP8Ni87/vFjuYBlrnAIVWVhn1x0+PF8/GS 5gRBTo9Uw==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lMy89-005v7j-2N; Thu, 18 Mar 2021 19:16:25 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lMy84-005v72-Te for linux-nvme@lists.infradead.org; Thu, 18 Mar 2021 19:16:22 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id A759664F01; Thu, 18 Mar 2021 19:16:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616094979; bh=RSgnT3FiumcLKGFMP9P0n/DXtn+x8TbcsrdPfxWACvk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=n6Ns1yaQkO5VhdToxM50Cy4X75sdHdF51/cZ3FqHMRyC6eIYpWkvux5oBNdoR8MsL 6X3nUkDL1/l4oXH9TPKdK+PP6PoZdUNn0Jsh8ILX41T2uv0JOPXgiURUMCfZGp8Lfg j2MaLyE/zPKE9GvrjlSaVmCn1+ncUu/KClSppZx9pXIy+0CUytfx8j53yBduDXt3kv hyqnAZkYcXEaAliSN0u255LJoPCvQdOuR5dFAFH17Zl/fCimNGCz01FLTW6yZndmdK X92G5rZHIJB4pFBXoqPyiQbzLvHH9pEqikxb7iyN/fOs2Y+FxreGrfyHnYMYrpmdKU lUtltC2yfXtiw== Date: Fri, 19 Mar 2021 04:16:13 +0900 From: Keith Busch To: Sagi Grimberg Cc: Chao Leng , Christoph Hellwig , linux-nvme@lists.infradead.org, Chaitanya Kulkarni Subject: Re: [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs Message-ID: <20210318191613.GB31675@redsun51.ssa.fujisawa.hgst.com> References: <20210315222714.378417-1-sagi@grimberg.me> <1b2ccda9-5789-e73a-f0c9-2dd40f320203@grimberg.me> <20210316204204.GA23332@redsun51.ssa.fujisawa.hgst.com> <59f7a030-ea33-5c31-3c18-197c5a12e982@grimberg.me> <17b15849-f0f3-af61-113f-0eb717e96f0f@huawei.com> <20210317065910.GC14498@lst.de> <2e391aae-58c7-b8f7-1a9e-d7ad5bb3f8f3@huawei.com> <6c085430-cc10-a2fd-56ee-a360109c940a@grimberg.me> <55142c25-9a70-08a0-d46a-cad21da59d19@huawei.com> <7b7d5223-ddaf-eb88-f112-02834f8c8f93@grimberg.me> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7b7d5223-ddaf-eb88-f112-02834f8c8f93@grimberg.me> User-Agent: Mutt/1.12.1 (2019-06-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210318_191621_177589_B3F7EEAE X-CRM114-Status: GOOD ( 12.49 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Thu, Mar 18, 2021 at 11:46:08AM -0700, Sagi Grimberg wrote: > > Placing the request on the requeue_list is fine, but the question is > when to kick the requeue_work, nothing guarantees that an alternate path > exist or will in a sane period. So constantly requeue+kick sounds like > a really bad practice to me. nvme_mpath_set_live(), where you reported the deadlock, kicks the requeue_list. The difference that NOWAIT provides is that nvme_mpath_set_live's schronize_srcu() is no longer blocked forever because the .submit_bio() isn't waiting for entery on a frozen queue, so now it's free to schedule the dispatch. There's probably an optimization to kick it sooner if there's a viable alternate path, but that could be a follow on. If there's no immediate viable path, then the requests would remain on the requeue list. That currently happens as long as there's a potential controller in a reset or connecting state. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme