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 458FFFCE08A for ; Thu, 26 Feb 2026 14:04:48 +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:Content-Type:In-Reply-To: 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=nGVLntgS7y17jrtUPVq3eOV3I3Dp+Pz66Cj+hxDGxis=; b=REtft215npzZgKM2b50oHqhchN eMGDNeHPqOdo/KzY7vRpl/sAjwTmOkNDzpKhm+yv0gzAbPWBtL0N5lUO8nNOblG2GAyQDrCfm7mMc m757HQ9x2k4gQ8SKYT2uFZFcQ21d+ks+HzK6auZsltk++CFypBlJexN2/NHxHbhZVPl8ysRimxlLX Fj5jEAhU+yTQlGuKwt7p9eRLaWweM5T0bListqgEWiCV6p9qWzrN0X58pp7l73rXmOC/kcelYTYVw Q8E49VDMUXP9QjADJnvNqnpauaIIbP4+xzkhldtWrANgsPvNxO+KyBapKnNu9QcD57akEmxDUJX8D G0z3aSxg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vvbyv-00000006HO9-02yT; Thu, 26 Feb 2026 14:04:45 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vvbyr-00000006HN8-3fGC for linux-nvme@lists.infradead.org; Thu, 26 Feb 2026 14:04:43 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772114679; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=nGVLntgS7y17jrtUPVq3eOV3I3Dp+Pz66Cj+hxDGxis=; b=h+OCF7diVnx4f/p57mBWrIoYK8cLcBhSsXB8U6eO7AeppRzhC+NqNucEeV7pJXx87idIxE np+PgawXiBeNM3rqelVvVlCcAHwP+sFhM1Dt5skphyh9HDu8AAKNfWSYQaAhpTt/qeQWQm 40W7/zWNl5jGdsEL76J8DdKLHTMSSPQ= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-441-cd0trrkZNFKZDEH-N7NXbA-1; Thu, 26 Feb 2026 09:04:37 -0500 X-MC-Unique: cd0trrkZNFKZDEH-N7NXbA-1 X-Mimecast-MFC-AGG-ID: cd0trrkZNFKZDEH-N7NXbA_1772114675 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ED52D1956079; Thu, 26 Feb 2026 14:04:34 +0000 (UTC) Received: from fedora (unknown [10.72.116.93]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0EE591956053; Thu, 26 Feb 2026 14:04:25 +0000 (UTC) Date: Thu, 26 Feb 2026 22:04:18 +0800 From: Ming Lei To: Daniel Wagner Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Guangwu Zhang , Chengming Zhou , Thomas Gleixner , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 3/3] Revert "lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly" Message-ID: References: <20260226-revert-cpu-read-lock-v1-0-eb005072566e@kernel.org> <20260226-revert-cpu-read-lock-v1-3-eb005072566e@kernel.org> MIME-Version: 1.0 In-Reply-To: <20260226-revert-cpu-read-lock-v1-3-eb005072566e@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: 63-EnvEnetIMDSxzCse1NPSFGClapaCznPxMVrq9xvg_1772114675 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260226_060442_048482_61AB1995 X-CRM114-Status: GOOD ( 15.25 ) 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 Thu, Feb 26, 2026 at 02:40:37PM +0100, Daniel Wagner wrote: > This reverts commit 0263f92fadbb9d294d5971ac57743f882c93b2b3. > > The reason the lock was removed was that the nvme-pci driver reset > handler attempted to acquire the CPU read lock during CPU hotplug > offlining (holds the CPU write lock). Consequently, the block layer > offline notifier callback could not progress because in-flight requests > were detected. > > Since then, in-flight detection has been improved, and the nvme-pci > driver now explicitly updates the hctx state when it is safe to ignore > detected in-flight requests. As a result, it's possible to reintroduce > the CPU read lock in group_cpus_evenly. Can you explain your motivation a bit? Especially adding back the lock causes the API hard to use. Any benefit? Thanks, Ming