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=-2.5 required=3.0 tests=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 7E32BC43331 for ; Thu, 2 Apr 2020 16:00:17 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 4F6CA20787 for ; Thu, 2 Apr 2020 16:00:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="l5GpgxeD"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="WKXaO27f" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F6CA20787 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=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=au5cV4Xy49abVnBcVmO1oBGTnordZjDr74YQqYGt4Gc=; b=l5GpgxeDE6Z70s uzldFyZX2zYEgJr6ISAKD6JrzhKMsmlP8l7VhqPJ7L3VNWFPRqr8XAd+460O6w7No4DZKle+T5Bmo VEllJvRrdaUYPeljR5RLGG9nXRM4rZ1qzatxcrRQUjX5wkZ9O3nqXuPO61hawwjpG9qayUbrkL9Hd 4LOQs875GCdssD6Hbb5fqGouBTVMLlsYW7QgEkdo7PjlRNoS5GiDDZqvs3LL4iGSe0wm/KcGyaStJ ddmPnVCByyaw3ocTwK6PAuRyjVJpsPmsQwV2W5xcC7K8fCJMpb5qYJEo/vt/4tZsWRgYQrcNpow95 ijZGVis1pNpS5kjpaQFA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jK2GM-0000AN-3L; Thu, 02 Apr 2020 16:00:14 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jK2GI-0007l5-Rj for linux-nvme@lists.infradead.org; Thu, 02 Apr 2020 16:00:12 +0000 Received: from redsun51.ssa.fujisawa.hgst.com (unknown [199.255.47.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8D55420757; Thu, 2 Apr 2020 16:00:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585843210; bh=u13NspfbPn6HGrv8/23zR/4+TjO9HEvQIFhO7dlEeRk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WKXaO27f8N2YUH06hK1Q8jeduOVUW3mmgTSVA0VeIhDEY5XkQb3wr6ONaW7cWf4vx vvn6LyhXj0nFmrq8naJRGXOTcQ719wAwnIe2wJiOpzJTFgwDhh7xTWlmltvtrYt/8f uPMDU6YEOimXtzRawTA6eDlF3UlYs6vvfdrxIYRI= Date: Fri, 3 Apr 2020 01:00:03 +0900 From: Keith Busch To: Sagi Grimberg Subject: Re: nvme deadlock with ANA Message-ID: <20200402160003.GA3901@redsun51.ssa.fujisawa.hgst.com> References: <5e38c566-3f26-288d-1004-161d1084b468@grimberg.me> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5e38c566-3f26-288d-1004-161d1084b468@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-20200402_090010_939886_22559BB4 X-CRM114-Status: GOOD ( 14.72 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anton Eidelman , Christoph Hellwig , linux-nvme , Hannes Reinecke 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 Wed, Mar 25, 2020 at 11:23:50PM -0700, Sagi Grimberg wrote: > Hey, > > I want to consult with you guys on a deadlock condition I'm able to > hit with a test that incorporate controller reconnect, ana updates > and live I/O with timeouts. > > This is true for NVMe/TCP, but can also happen in rdma or pci drivers as > well. > > The deadlock combines 4 flows in parallel: > - ns scanning (triggered from reconnect) > - request timeout > - ANA update (triggered from reconnect) > - FS I/O coming into the mpath device > > (1) ns scanning triggers disk revalidation -> update disk info -> > freeze queue -> but blocked, why? > > (2) timeout handler reference the g_usage_counter - > but blocks in > the timeout handler, why? > > (3) the timeout handler (indirectly) calls nvme_stop_queue() -> which > takes the namespaces_rwsem - > but blocks, why? > > (4) ANA update takes the namespaces_rwsem -> calls nvme_mpath_set_live() > -> which synchronize the ns_head srcu (see commit 504db087aacc) -> > but it blocks, why? Why is ana updating occuring under a write lock? AFAIK, that should be necessary only if it's manipulating the ctrl->namespaces list, but this is just iterating it. What's the harm in using the read lock here? > (5) FS I/O came into nvme_mpath_make_request -> took srcu_read_lock -> > direct_make_request > blk_queue_enter -> but blocked, why? > > ==> because of (1), the request queue is under freeze -> deadlock. _______________________________________________ linux-nvme mailing list linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme