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 E6F37C27C65 for ; Tue, 11 Jun 2024 16:40:08 +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=wC5OZnq3v1yIVM8bLFl+GWjkjb1gTIbLriEcW2SBytQ=; b=VftSmTAdm50dHGuLBCbZhfMyi1 vxVIR+Zz6VkoSXAEsK2mEUTP9aEaH7pGO1HgKgJmNWsAjRUPVE5xrdc6J8Af+770fclN1IS0pZ17Q 736Kkz8hSOP+GdR2zFZX82HVKAGuDx+7wlitgqxTA/7klkmQmPtr1t3NnA1YIqQvJlA9p5lhrFiG+ RAGszzjC3XPe/vx77voQePn7TICG/4uJhf+NKM5rUR74LJrDSkiSOmrS7/W/zzzVoGtBHlMLN7Ev1 wcIJgq1wI3obP5R8pGCugHXGkA2QE7Rf9791BPNaRQ2pdfXhppJR7yl1BMrHZmj0budHU38NdZ1Ug DgV2V3rg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sH4XU-00000009Xcl-0EZG; Tue, 11 Jun 2024 16:40:04 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sH4XR-00000009XbN-0BHZ for linux-nvme@lists.infradead.org; Tue, 11 Jun 2024 16:40:02 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id A473868BEB; Tue, 11 Jun 2024 18:39:55 +0200 (CEST) Date: Tue, 11 Jun 2024 18:39:55 +0200 From: Christoph Hellwig To: Keith Busch Cc: linux-nvme@lists.infradead.org, hch@lst.de, sagi@grimberg.me, Keith Busch , Venkat Rao Bagalkote , "Paul E. McKenney" , rcu@vger.kernel.org Subject: Re: [PATCH] nvme: fix namespace removal list Message-ID: <20240611163955.GA12787@lst.de> References: <20240611152055.2317197-1-kbusch@meta.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240611152055.2317197-1-kbusch@meta.com> 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-20240611_094001_274526_B26746D4 X-CRM114-Status: GOOD ( 12.83 ) 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, Jun 11, 2024 at 08:20:55AM -0700, Keith Busch wrote: > mutex_lock(&ctrl->namespaces_lock); > list_for_each_entry_safe(ns, next, &ctrl->namespaces, list) { > - if (ns->head->ns_id > nsid) > - list_splice_init_rcu(&ns->list, &rm_list, > - synchronize_rcu); > + if (ns->head->ns_id > nsid) { > + list_del_rcu(&ns->list); > + list_add_tail_rcu(&ns->list, &rm_list); > + } Is this actually valid for a (S)RCU protected list? If the entry gets added to the new list before the grace period has completed, we could trick a concurrent traversal into following the new list unless I'm mistaken (although chances I'm mistaken on RCU corner cases aren't that low..).