From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 815C85661; Fri, 16 May 2025 15:48:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747410524; cv=none; b=SCTV6vIiiDPXYODW+EWvqRcO6JmTNRpq2TJCHvckI/5PR3UJ8B4ERDt1O8Yev73XCfRR3zGziuLqb8UbGUbNbR2M7c/avrAP1zlzf+uEB399B6h6iko+HWfZb5FtMkseySQcPbAaage3CKj1RbxD3knLNhm1yDSATkW+I/56qvU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747410524; c=relaxed/simple; bh=YwkrdAsWoKSTg4VyvIMwADPTVOl64Ko9498w1w+F5+o=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=QhY8Yjg7UGtQTcX2wxQzCT10+jjdZH8E8NIt/A7vWMopgKrx94+e7CJ335Sz6ANQJyj6HQZjHTY8BpS+Vq6EPkAV3c9HjhuJ7LL8NR3lvQaI7Smf6hfdMMKwL1oJQ+QNPcbXCcKjWO/BIUe8gpq7oOtzYQzh3WqCHfhTDgK6W+k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KY1DIJmd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KY1DIJmd" 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> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?oC7thKeshSt8CSsSDO4dPBzhmkLQfhM28Akcu7BwdGqwjvSlw9Reb2zA5iz4?= =?us-ascii?Q?DRYBQiETg5DKRLkQbnUGBCPSs5BlIC608ZeduYdWAkpivZDJkSF1h6u5bZqI?= =?us-ascii?Q?oQfuaWilfXUYhWrf2GFaiNru9LtkGXIZK3y4NXtW1CBjDB+g0pq1EqEBrb06?= =?us-ascii?Q?8wX1r5bVTSV9W3NmZkui/6UgrjsbJK/MWzwIA2cPYEQi+9EE4Ri/Yaf0QsbA?= =?us-ascii?Q?CLNQavJKypuMsAahNSbLWOVertIryZNDj3sYfY4ERArkCvxbV7TYjB85r3Td?= =?us-ascii?Q?rdYpf4uom4LHVSYAMsMIvmVU7Q1lHcEqwRg7hF6sFNV2PIZxWgwNOUf5xeox?= =?us-ascii?Q?bEcYYo5/Niw+G0iFgtlW93D2Jc9V/d6tsQwD2Me1JHJ+/d/b/93HCpUlxEjp?= =?us-ascii?Q?c4wNp53OiGqxn3XB/jF4SWJAX8tu9Ik2Ocwqf0KU9rUrmOLXwldSgIKVmcPG?= =?us-ascii?Q?QivBPZUTR3Ul2UpbIloUEnh7jJ0OcUnCeu/kur/3MgvOBbCLpgUAR+OoeFxR?= =?us-ascii?Q?bgibzbMs3pnbIyfN8JsCVwXi5VfYp5/TXgBMv5DR/DPBgNkYzEca3jkZrWwT?= =?us-ascii?Q?j6EExsQ9oTFB6us/fulMaFY/yE5vPn6QHQc+ZubNfP5SzxsSuItwSUMFxeGv?= =?us-ascii?Q?pRLAd0Xnh7HnWKF7CPhfq+Les2PY7SwRnjYf9nVkrNJqOrA3HHLghAQ3ORjF?= =?us-ascii?Q?CEzsd1glsGDQaIHdsLVDMEvtg/Z9jl2KTjPLzh9/6d0m/h38J0Jzkg5i9YR5?= =?us-ascii?Q?5OxKsrxWqtqqLB+FRRUAH6Ew/pmdZrAEjmmfU3Jjq2X+WrffTt+POCU9fNpL?= =?us-ascii?Q?igxxBb+w2zwCJ9o7kGMWKbwxPeQY2qTGkQ5sZBIfRR16UE6hyO5pM06Gc35X?= =?us-ascii?Q?thJztXwyz+Ajs4T2AOUlKT/5IwL0OiyKOliM4/Y3dkPCCYrGCshJqDqRtYfc?= =?us-ascii?Q?PKuM+7EB74aMXT+w1Oa33F837h/3B9iex4qpuKKzgKojEUNsWTDD4GLADbVa?= =?us-ascii?Q?gtCLd+P3mTZE1+Tz0sMnj6b29TtUK9Q+9OBsvuizUxIHlwmKUReqyKM8g596?= =?us-ascii?Q?UrlzoENGR7c8tqmTV3/5sx15N93HvW7UkP5hM6SZfaUL4r7u9aUtwAwBgsDV?= =?us-ascii?Q?JCmMdv3dBr454a83GPqmPPZqX+qWvZ1cc1nmTriXHDiF73+RkEi8fHoh7QEK?= =?us-ascii?Q?316p4XDAUGl0h/esp9T1K4jKriSK3kXsU3xViE35uiLXpBPaKvy8dpR5VuJ2?= =?us-ascii?Q?HC/5XT0vumBaHKPrLqKj5Ce7WnnF8WHPDnd3sc5LxdCEgz7n2zh29q9z29I5?= =?us-ascii?Q?lPJMnpfEhfuSFUZpSQeZfMXS0A2WSfsEEC3cY9CrIEZBzCTSzmEkNNyBoBL0?= =?us-ascii?Q?GqB0552w+nlzDTlPwWqqDx+BlmpGi0YmlQ+4yRpQ/S/5+J4kuWlH/0AEGfCu?= =?us-ascii?Q?rC050VoXGdzUAdkVYBlDrCO33Od3NlOQk7n5JuUnbzaddAzqdd85rcdBh8wJ?= =?us-ascii?Q?wTh99kUs+ruo03cdo614iO/P+tHPBfSxi7r9f/tiRhxEQVULoKM7biMqIklN?= =?us-ascii?Q?SiPeFDc99UG48GhBJrhxtGBXWaZ+CJajt5AyTy6kN85pDbj3NCVcpEzSa0WY?= =?us-ascii?Q?JA=3D=3D?= X-OriginatorOrg: fibocom.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7714b799-1fe7-4e2c-1d6f-08dd976cbd5f X-MS-Exchange-CrossTenant-AuthSource: TY0PR02MB5766.apcprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 May 2025 07:05:44.9644 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 889bfe61-8c21-436b-bc07-3908050c8236 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 79LZqJvmDLORSHM6ugnYlq7gDsBxCG+8L3cUfQYf7m9J/sHTdvgafJTalAOytSOPe/d3h9RbUatOFAxRm5huKVkL31ul+Q7TOZLL9/Lw1qI= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2PR02MB5673 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.