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 A5B54C54754 for ; Fri, 16 May 2025 16:15:05 +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-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To: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=K0ZiU/DcoSa/seEPcSuNMjaWR2VHG04R0HPlpttYXqM=; b=VRIWQHsdO0pj+KAacagP/s4+EF cJmyeRhJ8cMm/un25NuG9/88M0lEXbIyLL8Ikpoe9A3eS5mJWgvk/ZKCCFbetqmb/lTqU+wrafpNv +DPrKxNLCRaVPrBm859BIkGmI+QLCufZokjLobxhjrdmiSv6VPUMutD/ebRFo7g93szxAOMMbnn0c ZcMlWra8iR18fPHla1Ug4S7fCJbi6/t6JNdEA5wy6OTZgLsAX6KjD7Y9jltImGx7R39WHdDxclqbC cLP/OtRWqpbvMIgds7ZipwTWrry58tvLTAk2Al4ecfDWptCxdPimZ2Af5B+3oMTs6JUZddutFgOv2 NTmAw8DA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uFxi6-00000003z9k-27JR; Fri, 16 May 2025 16:14:58 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uFxIi-00000003uNI-29Xj; Fri, 16 May 2025 15:48:45 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 202CC4A8B1; Fri, 16 May 2025 15:48:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 513B8C4CEE4; Fri, 16 May 2025 15:48:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747410524; bh=YwkrdAsWoKSTg4VyvIMwADPTVOl64Ko9498w1w+F5+o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=KY1DIJmdEOjykVGmXpktVEaoBzevy5wMtkqjEZljk71vzm2nLkxE+xKQCVABROLH3 J2yWPNtA5bC96cIUKUflcR25hDaxENp8fqasS975RreMjoyKl7fTbF4g2RIn5uXoQF u21mcgYMDYn8WsTnp3KPbPxtZn9ik0hO7nmrS799zCrAwv7ZjLEUCOjQR+fJKyND4Q 6obyKZdRJPLXfVgUWFu1RCrGNuHzLwAZrgd87/gqvsd+44OiDcuJqvIPutFW1cBXdY 8/+d9sgXWCav4LUg8sbB6JUD8vwBV+OAoee1dzzFEjehxNl3MPObiLZYk740MIsuQj 3OiGxhe/DTc/g== Date: Fri, 16 May 2025 08:48:42 -0700 From: Jakub Kicinski To: Jinjian Song Cc: andrew+netdev@lunn.ch, angelogioacchino.delregno@collabora.com, chandrashekar.devegowda@intel.com, chiranjeevi.rapolu@linux.intel.com, corbet@lwn.net, danielwinkler@google.com, davem@davemloft.net, edumazet@google.com, haijun.liu@mediatek.com, helgaas@kernel.org, horms@kernel.org, johannes@sipsolutions.net, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, loic.poulain@linaro.org, m.chetan.kumar@linux.intel.com, matthias.bgg@gmail.com, netdev@vger.kernel.org, pabeni@redhat.com, ricardo.martinez@linux.intel.com, ryazanov.s.a@gmail.com Subject: Re: [net v1] net: wwan: t7xx: Fix napi rx poll issue Message-ID: <20250516084842.26c80cb5@kernel.org> In-Reply-To: <20250515175251.58b5123f@kernel.org> References: <20250515031743.246178-1-jinjian.song@fibocom.com> <20250515175251.58b5123f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250516_084844_572611_3F2DC34A X-CRM114-Status: UNSURE ( 7.39 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@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-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 16 May 2025 15:30:38 +0800 Jinjian Song wrote: > It seems that a judgment is made every time ccmni_inst[x] is used in the driver, > and the synchronization on the 2 way might have been done when NAPI triggers > polling by napi_schedule and when WWAN trigger dellink. Synchronization is about ensuring that the condition validating by the if() remains true for as long as necessary. You need to wrap the read with READ_ONCE() and write with WRITE_ONCE(). The rest if fine because netdev unregister sync against NAPIs in flight. 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Received: from TY0PR02MB5766.apcprd02.prod.outlook.com (2603:1096:400:1b5::6) by SG2PR02MB5673.apcprd02.prod.outlook.com (2603:1096:4:1cc::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8746.30; Tue, 20 May 2025 07:05:45 +0000 Received: from TY0PR02MB5766.apcprd02.prod.outlook.com ([fe80::f53d:47b:3b04:9a8b]) by TY0PR02MB5766.apcprd02.prod.outlook.com ([fe80::f53d:47b:3b04:9a8b%5]) with mapi id 15.20.8746.030; Tue, 20 May 2025 07:05:45 +0000 From: Jinjian Song To: kuba@kernel.org Cc: andrew+netdev@lunn.ch, angelogioacchino.delregno@collabora.com, chandrashekar.devegowda@intel.com, chiranjeevi.rapolu@linux.intel.com, corbet@lwn.net, danielwinkler@google.com, davem@davemloft.net, edumazet@google.com, haijun.liu@mediatek.com, helgaas@kernel.org, horms@kernel.org, jinjian.song@fibocom.com, johannes@sipsolutions.net, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, loic.poulain@linaro.org, m.chetan.kumar@linux.intel.com, matthias.bgg@gmail.com, netdev@vger.kernel.org, pabeni@redhat.com, ricardo.martinez@linux.intel.com, ryazanov.s.a@gmail.com, liuqf@fibocom.com Subject: Re: [net v1] net: wwan: t7xx: Fix napi rx poll issue Date: Tue, 20 May 2025 15:05:34 +0800 Message-ID: <20250516084842.26c80cb5@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250516084842.26c80cb5@kernel.org> References: <20250515031743.246178-1-jinjian.song@fibocom.com> <20250515175251.58b5123f@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org Content-Type: text/plain; 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X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Message-ID: <20250520070534.1oUA0bV-tYQJcBqo26IFITRR0AUqa3Ri2TNPBChlzVE@z> >On Fri, 16 May 2025 15:30:38 +0800 Jinjian Song wrote: >> It seems that a judgment is made every time ccmni_inst[x] is used in the driver, >> and the synchronization on the 2 way might have been done when NAPI triggers >> polling by napi_schedule and when WWAN trigger dellink. > >Synchronization is about ensuring that the condition validating >by the if() remains true for as long as necessary. >You need to wrap the read with READ_ONCE() and write with WRITE_ONCE(). >The rest if fine because netdev unregister sync against NAPIs in flight. > Hi Jakub, I think I got your point. I can use the atomic_t usage in struct t7xx_ccmni to synchronization. static void t7xx_ccmni_wwan_dellink(...) { [...] if (WARN_ON(ctlb->ccmni_inst[if_id] != ccmni)) return; unregister_netdevice(dev); //Add here use this variable(ccmnii->usage) to synchronization if (atomic_read(&ccmni->usage) == 0) ccmni == NULL; } How about this modify? Thanks. Jinjian, Best Regards.