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15.21.0223.011; Fri, 17 Jul 2026 03:42:38 +0000 Message-ID: <70f854e7-b066-4f30-8ebf-71abdece45c2@windriver.com> Date: Fri, 17 Jul 2026 11:42:28 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tty: ldisc: fix deadlock between ldisc_sem and rtnl_mutex To: "Jagielski, Jedrzej" , "gregkh@linuxfoundation.org" , "jirislaby@kernel.org" , "socketcan@hartkopp.net" , sdf.kernel@gmail.com Cc: "linux-serial@vger.kernel.org" , "mkl@pengutronix.de" , "linux-can@vger.kernel.org" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" , "horms@kernel.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20260716064719.1401892-1-yun.zhou@windriver.com> Content-Language: en-US From: "Zhou, Yun" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SE2P216CA0005.KORP216.PROD.OUTLOOK.COM (2603:1096:101:117::16) To CH0PR11MB5332.namprd11.prod.outlook.com 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definitions=main-2607170032 Hi Jagielski, On 7/16/26 15:59, Jagielski, Jedrzej wrote: > CAUTION: This email comes from a non Wind River email account! > Do not click links or open attachments unless you recognize the sender and know the content is safe. > > From: Yun Zhou > Sent: Thursday, July 16, 2026 8:47 AM > >> syzbot reported a circular lock dependency involving tty ldisc_sem and >> the networking rtnl_mutex. The full chain is: >> >> rtnl_mutex --> nft_commit_mutex --> ... --> ep->mtx --> ldisc_sem --> rtnl_mutex > > still unclear where the first mutex may come from tty_set_ldisc() tty_ldisc_lock() <- hold ldisc_sem tty_ldisc_open() slcan_open() register_candev() register_netdev() rtnl_net_lock_killable() <- hold rtnl_mutex > >> >> + tty_ldisc_unlock(tty); >> >> + /* > > this blank line is redundant i believe > Isn't it common practice to leave the first line of a multi-line comment blank? Does it violate the coding style guidelines? BR, Yun