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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id DEE5FC004D4 for ; Wed, 18 Jan 2023 07:38:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=7fAxybDGipH02vputEuYiufbK7FziGeQOCUU7EzR338=; b=HPFoiTNaqKEWwLN9JgaMfKcOf6 tI7Qxsp7E/bWjFsxA6Jeexhs6BskFkA35uuAMKy1QjiJZ6IVo9waHnlsud/m4QBPP4N4NrUglAbrh KhrYwYGRZDywgzdSzHWTiO19MBOYgIjZEuwuHH8GzLILcs6tebalXYugrgyYNs4v2vSAyf9glG4YZ yPH014W41Jk5h/rLVKz78Ph5vo/ner5VJB6ib0nIK6pzYcsYEvJCaoYGG01v7mXxxT2Abkm/fuNnj n2rsx8k2n+O24+hgXXaQjaHkS0a1NXYKcRFml5pfhXxfzX03C9U3YJt8ELuRUXRjOc4lqrPFzRUaI jlyMoFIA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pI325-00HH9z-CX; Wed, 18 Jan 2023 07:38:53 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pI2x2-00HEwG-Mq for linux-nvme@lists.infradead.org; Wed, 18 Jan 2023 07:33:42 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 2DE2067373; Wed, 18 Jan 2023 08:33:31 +0100 (CET) Date: Wed, 18 Jan 2023 08:33:30 +0100 From: Christoph Hellwig To: Keith Busch Cc: Christoph Hellwig , Keith Busch , linux-nvme@lists.infradead.org, sagi@grimberg.me, Jens Axboe Subject: Re: [PATCHv2] nvme-pci: fix timeout request state check Message-ID: <20230118073330.GA27048@lst.de> References: <20230118052244.741505-1-kbusch@meta.com> <20230118053306.GA24817@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230117_233340_924401_DFBBD78B X-CRM114-Status: GOOD ( 15.62 ) 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: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Jan 17, 2023 at 10:52:39PM -0700, Keith Busch wrote: > We're actually not batching here (no IOB in the timeout context), so we > are either: > > a. calling nvme_pci_complete_rq() inline with the cqe > b. racing with smp ipi or softirq > > If case (a), we will always see IDLE. If (b), we are racing and may see > either COMPLETED or IDLE, so we have to check that it's not either of > those. Since there's only one other state (STARTED) that was guaranteed > prior to entering the timeout handler, we can just make sure it's not > that one after the poll to know if abort escalation is needed. The point is still that "started" is the wrong check here and relies on an implementation detail. I think we're better off with an explicit IDLE check and a big fat comment.