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Received: from TY0PR02MB5766.apcprd02.prod.outlook.com (2603:1096:400:1b5::6) by SI2PR02MB5955.apcprd02.prod.outlook.com (2603:1096:4:1e6::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8251.20; Mon, 16 Dec 2024 13:53:56 +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 15.20.8251.015; Mon, 16 Dec 2024 13:53:55 +0000 From: Jinjian Song To: ryazanov.s.a@gmail.com, Jinjian Song , chandrashekar.devegowda@intel.com, chiranjeevi.rapolu@linux.intel.com, haijun.liu@mediatek.com, ricardo.martinez@linux.intel.com, loic.poulain@linaro.org, johannes@sipsolutions.net, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: andrew+netdev@lunn.ch, angelogioacchino.delregno@collabora.com, corbet@lwn.net, danielwinkler@google.com, helgaas@kernel.org, horms@kernel.org, korneld@google.com, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, matthias.bgg@gmail.com, netdev@vger.kernel.org Subject: Re: [net v2] net: wwan: t7xx: Fix FSM command timeout issue Date: Mon, 16 Dec 2024 21:53:22 +0800 Message-Id: <20241216135322.4533-1-jinjian.song@fibocom.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: <20241213064720.122615-1-jinjian.song@fibocom.com> Content-Language: en-US Content-Type: text/plain; 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X-BeenThere: linux-mediatek@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-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org From: Sergey Ryazanov >> Fixes: d785ed945de6 ("net: wwan: t7xx: PCIe reset rescan") > >The completion waiting was introduced in a different commit. I believe, >the fix tag should be 13e920d93e37 ("net: wwan: t7xx: Add core components") > Got it. [...] >> if (cmd->flag & FSM_CMD_FLAG_WAIT_FOR_COMPLETION) { >> *cmd->ret = result; > >The memory for the result storage is allocated on the stack as well. And >writing it unconditionally can cause unexpected consequences. > Got it. [...] >> wait_ret = wait_for_completion_timeout(&done, >> msecs_to_jiffies(FSM_CMD_TIMEOUT_MS)); >> - if (!wait_ret) >> + if (!wait_ret) { >> + cmd->done = NULL; > >We cannot access the command memory here, since fsm_finish_command() >could release it already. > Got it. [...] >Here we have an ownership transfer problem and a driver author has tried >to solve it, but as noticed, we are still experiencing issues in case of >timeout. > >The command completion routine should not release the command memory >unconditionally. Looks like the references counting approach should help >us here. E.g. >1. grab a reference before we put a command into the queue >1.1. grab an extra reference if we are going to wait the completion >2. release the reference as soon as we are done with the command execution >3. in case of completion waiting release the reference as soon as we are >done with waiting due to completion or timeout > >Could you try the following patch? Please note, besides the reference >counter introduction it also moves completion and result storage inside >the command structure as advised by the completion documentation. > Yes, please let me try the following patch. [...] Thanks. Jinjian, Best Regards.