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([2001:67c:2fbc:1:83ac:73b4:720f:dc99]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-acaa1bb312bsm1056251366b.15.2025.04.15.00.42.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Apr 2025 00:42:20 -0700 (PDT) Message-ID: <6ec928b7-6980-4e9a-bab5-654c91db4a95@mandelbit.com> Date: Tue, 15 Apr 2025 09:42:18 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tracing: fprobe: Fix RCU warning message in list traversal To: Breno Leitao , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com References: <20250410-fprobe-v1-1-068ef5f41436@debian.org> Content-Language: en-US From: Antonio Quartulli Autocrypt: addr=antonio@mandelbit.com; keydata= xsFNBFN3k+ABEADEvXdJZVUfqxGOKByfkExNpKzFzAwHYjhOb3MTlzSLlVKLRIHxe/Etj13I X6tcViNYiIiJxmeHAH7FUj/yAISW56lynAEt7OdkGpZf3HGXRQz1Xi0PWuUINa4QW+ipaKmv voR4b1wZQ9cZ787KLmu10VF1duHW/IewDx9GUQIzChqQVI3lSHRCo90Z/NQ75ZL/rbR3UHB+ EWLIh8Lz1cdE47VaVyX6f0yr3Itx0ZuyIWPrctlHwV5bUdA4JnyY3QvJh4yJPYh9I69HZWsj qplU2WxEfM6+OlaM9iKOUhVxjpkFXheD57EGdVkuG0YhizVF4p9MKGB42D70pfS3EiYdTaKf WzbiFUunOHLJ4hyAi75d4ugxU02DsUjw/0t0kfHtj2V0x1169Hp/NTW1jkqgPWtIsjn+dkde dG9mXk5QrvbpihgpcmNbtloSdkRZ02lsxkUzpG8U64X8WK6LuRz7BZ7p5t/WzaR/hCdOiQCG RNup2UTNDrZpWxpwadXMnJsyJcVX4BAKaWGsm5IQyXXBUdguHVa7To/JIBlhjlKackKWoBnI Ojl8VQhVLcD551iJ61w4aQH6bHxdTjz65MT2OrW/mFZbtIwWSeif6axrYpVCyERIDEKrX5AV rOmGEaUGsCd16FueoaM2Hf96BH3SI3/q2w+g058RedLOZVZtyQARAQABzSlBbnRvbmlvIFF1 YXJ0dWxsaSA8YW50b25pb0BtYW5kZWxiaXQuY29tPsLBrQQTAQgAVwIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUJFZDZMhYhBMq9oSggF8JnIZiFx0jwzLaPWdFMBQJhFSq4GBhoa3Bz Oi8va2V5cy5vcGVucGdwLm9yZwAKCRBI8My2j1nRTC6+EACi9cdzbzfIaLxGfn/anoQyiK8r FMgjYmWMSMukJMe0OA+v2+/VTX1Zy8fRwhjniFfiypMjtm08spZpLGZpzTQJ2i07jsAZ+0Kv ybRYBVovJQJeUmlkusY3H4dgodrK8RJ5XK0ukabQlRCe2gbMja3ec/p1sk26z25O/UclB2ti YAKnd/KtD9hoJZsq+sZFvPAhPEeMAxLdhRZRNGib82lU0iiQO+Bbox2+Xnh1+zQypxF6/q7n y5KH/Oa3ruCxo57sc+NDkFC2Q+N4IuMbvtJSpL1j6jRc66K9nwZPO4coffgacjwaD4jX2kAp saRdxTTr8npc1MkZ4N1Z+vJu6SQWVqKqQ6as03pB/FwLZIiU5Mut5RlDAcqXxFHsium+PKl3 UDL1CowLL1/2Sl4NVDJAXSVv7BY51j5HiMuSLnI/+99OeLwoD5j4dnxyUXcTu0h3D8VRlYvz iqg+XY2sFugOouX5UaM00eR3Iw0xzi8SiWYXl2pfeNOwCsl4fy6RmZsoAc/SoU6/mvk82OgN ABHQRWuMOeJabpNyEzA6JISgeIrYWXnn1/KByd+QUIpLJOehSd0o2SSLTHyW4TOq0pJJrz03 oRIe7kuJi8K2igJrfgWxN45ctdxTaNW1S6X1P5AKTs9DlP81ZiUYV9QkZkSS7gxpwvP7CCKF n11s24uF1c7ATQRmaEkXAQgA4BaIiPURiRuKTFdJI/cBrOQj5j8gLN0UOaJdetid/+ZgTM5E HQq+o1FA50vKNsso9DBKNgS3W6rApoPUtEtsDsWmS0BKEMrjIiWOTGG8Mjyx6Z9DlYT/UmP8 j9BT7hVeGR3pS++nJC38uJa/IB+8TE8S+GIyeyDbORBsFD8zg2ztyTTNDgFMBXNb8aqhPbPT eaCnUWHGR/Mcwo9DoiYSm5jlxlNDCsFSBaJ/ofMK1AkvsilrZ8WcNogdB6IkbRFeX+D3HdiX BYazE4WulZayHoYjQyjZbaeSKcQi2zjz7A0MEIxwyU5oxinIAjt9PnOIO4bYIEDTrRlPuqp2 XptpdQARAQABwsF8BBgBCAAmFiEEyr2hKCAXwmchmIXHSPDMto9Z0UwFAmZoSRcCGwwFCQHh M4AACgkQSPDMto9Z0UxtFQ//S3kWuMXwpjq4JThPHTb01goM33MmvQJXBIaw18LxZaicqzrp ATWl3rEFWgHO7kicVFZrZ53p3q8HDYFokcLRoyDeLDAFsSA+fgnHz1B9zMUwm8Wb4w1zYMsO uo3NpBKoHNDlK9SPGHyVD6KoCGLQw+/h7ZhtcPRE7I74hNGBBVkFVeg+bggkZhaCZWbE/fih RCEEzuKl8JVtw4VTk4+F33+OfUEIfOKv7+LR9jZn9p7ExgfBdQyFr+K2+wEcZwgRgqTs8v0U R+zCVur69agK1RNRzQCMOAHvoBxRXHEm3HGnK8RL1oXFYPtBz52cYmd/FUkjTNs3Zvft9fXf wF/bs24qmiS/SwGc0S2wPtNjiAHPhCG9E1IGWLQTlsZRuQzfWuHgjPbVCTRwLBH0P+/BBWyA +8aKhGqG8Va0uwS3/EqiU6ZRYD+M/SnzCdD7eNjpr8Mn6jkudUXMWpsrd9KiMpt+vdtjfeJl NKMNf0DgFyiFHKqGek1jIcvfqBo6c2c5z65cUJ2hCQjnfWFePMixWzY6V9G5+4OtbAC/56ba 45MGdFf2cXH2Q9I7jZOQUrnkOvkQN4E7e/fet5yxy4HxVU3nG+HQZXntCt772wmsSrsSz1br T1r4zTJElYkSMWcxr+OwZn5DIsPlBMvpIa5n2AojdbVJ8Vk7NXuEezE9Nno= Organization: Mandelbit SRL In-Reply-To: <20250410-fprobe-v1-1-068ef5f41436@debian.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/04/2025 14:22, Breno Leitao wrote: > When CONFIG_PROVE_RCU_LIST is enabled, fprobe triggers the following > warning: > > WARNING: suspicious RCU usage > kernel/trace/fprobe.c:457 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > #1: ffffffff863c4e08 (fprobe_mutex){+.+.}-{4:4}, at: fprobe_module_callback+0x7b/0x8c0 > > Call Trace: > fprobe_module_callback > notifier_call_chain > blocking_notifier_call_chain > > This warning occurs because fprobe_remove_node_in_module() traverses an > RCU list using RCU primitives without holding an RCU read lock. However, > the function is only called from fprobe_module_callback(), which holds > the fprobe_mutex lock that provides sufficient protection for safely > traversing the list. > > Fix the warning by specifying the locking design to the > CONFIG_PROVE_RCU_LIST mechanism. Add the lockdep_is_held() argument to > hlist_for_each_entry_rcu() to inform the RCU checker that fprobe_mutex > provides the required protection. > > Fixes: a3dc2983ca7b90 ("tracing: fprobe: Cleanup fprobe hash when module unloading") > Signed-off-by: Breno Leitao I just hit this issue and I verified that the patch actually solves it without causing side effects. FWIW Tested-by: Antonio Quartulli -- Antonio Quartulli CEO and Co-Founder Mandelbit Srl https://www.mandelbit.com