From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB20D4CA779 for ; Thu, 15 Oct 2026 08:17:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792052260; cv=none; b=d4qK2OuK4wZWDr8v4QbTDCsvaAzvgv5z5Qt5q7G083bOf61oxywtCMKhZ6NPxq5LInbD0I6JC92FffT8lX8XBd6dmHeHB874EbV14P5vxSgRy40SbvqqDJM7IApFt/P5ar/4Nclx3+xGPXbPOYe0eJXGM7Mx+N4kq0TdaYKgNOs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792052260; c=relaxed/simple; bh=/HnoRr6jTN7lhWQJjX7agqNJaK5Mj2EZ7UCIBTgv/SA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=aNb1XBcPIrVZkc0fNmmeyhRlhlHwxUOMNPiIijr4joBDZVct3mjCN7dqSNThNdPjPE528FyKX+FCxRlDXjN+W9kEiK+98+wC7dlUo16uLHHN+zrz2jHBebKZs43Od4wUpj26qNW62KGSeBrh3l0OlABGmDKxC+T6HuUUB1XR5Os= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=e++FoW80; arc=none smtp.client-ip=209.85.128.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="e++FoW80" Received: by mail-wm1-f41.google.com with SMTP id 5b1f17b1804b1-49ff680331aso19303345e9.3 for ; Thu, 15 Oct 2026 01:17:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1792052253; x=1792657053; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=1wKZanZE44fFdmkSv3uEQgs6bQ7hBbf+Whca0W3g7zo=; b=e++FoW80yrrKTpIUOVXRJksmP/Rz4CMOF+4us3VnOgQbFzr8aYizm9GIn5FnI7oEgr ELFqMrzysgT6TCRbOSYrSX5WYIaaqX8AhuakaMqnrzYePxceQO7S4RFn+jau0epVrwRz q510/y8ZeV8EBUO3d9ZbrCh6tuXOnlRWWGx3KjuNyflrxuM9KpEt758up6TauiET+NvF SXogO2LLRQQCrStH0nq/I4Em2az0J9mqHYU/5ukJsy2NDW07rAQOiEMCIMltvpN4PRIq k9ZGJqRUdgO4xxusBBvViw4oxgKtNzrn9tij6lSIkl7l9yE8R1iYN4uf1/tHSNzdel64 YZAA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792052253; x=1792657053; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=1wKZanZE44fFdmkSv3uEQgs6bQ7hBbf+Whca0W3g7zo=; b=ZoQqfd4XAEXyl2pLVFBT0qwEDZMwFKAzHQARRdSbd3dO5ZiKDvCScTHj+ZLRoC6DrQ lyg2H42WdZKEZa/avYPUUTAfTzOI1DJC7DFJSbMe1qZFYIXqbt209hatD3ju2P4yesHV rt0v+A3tPcGBTFbc6MMiNVS1oRPebtuGAP5XZkFgyODJF8nYJP/+QRDz8gDKR1l0EQxw 3WccRfSI0CTA7cPKhgLA1KZpgI3spvZO6nMbM5e4C/ArSzWnI0dn7fLRURPD5FJLdu0D uLTnK/drLyTb1eAPIFm+tQRl9x5IIFSCV4wYI7tZpFGOn6XAgXxR7LGjOVMxRKq2MQuZ AtkQ== X-Forwarded-Encrypted: i=1; AKwUvBx9rdjiqwhvLLMjkflj4hj4Y2epZwFDaQvWiC3AW11E5JInwcm7qia0U5WAbLdlE+o1NR+xcjc=@vger.kernel.org X-Gm-Message-State: AFq9FYJakjsD6i84AyYMEW3c3m0rvmvJPdW8OwljCrjTw2BYilmurGL0 I3mDOoeHTa3lZ7dbBjsVujxKTXnPOAT94RgWMX4YLtD/iunhm+F4tQvB X-Gm-Gg: AYBFou2hoVc8YxYdcpUF+J1w2PhsuxYcAPka05GIN+AxOoPto2e8Hg7qyYMWkSzvPZg GlSz+2Xg3uIkLeA27xC/aY6tihH/EN7xUUSKkaea3sWUXQiNb0YgQbWihMh0GB9q9RsBYEAfcnO iffNI4nSePMzbhUz0oWsEhP808de5G6Re9cQqy/Vev0rxYzM2Dyrse124Py3UpKgvCjJul8XwuS qaCIRhSXk+YPA1yPGrE4ybb5HBhcZR1pWnXm4nE9wVszjzrMnBUrKVTC1QokT3gxtt4cU7NPw0o 177uoF6JsFNadRMeRrc3sWk1X2hhHaR1VYR7iUR29KYTUbCMHyB55pRwZGmthj7408yJSVBlPTW AcO5KY56RY/ZQmLfvhl50fcmsYXFUOJfTuQUq7g/09L9/X9dBjytumAVmAjBBDnlxVSl9KQI5kf q0l2NvjsIgcm/1Bg8yFi9yEsNPGvs9L1q0oD/3MRi879axXs75sDDLoQgaLUIfcR0NebrwYkrSJ /l2disPbX1Wxuz8tyRQPtJqrG6kVkktKzPF5b7Vaj7png== X-Received: by 2002:a05:600c:524a:b0:4a1:8824:c9ba with SMTP id 5b1f17b1804b1-4a18e49234fmr374111135e9.18.1792052253328; Thu, 15 Oct 2026 01:17:33 -0700 (PDT) Received: from andreayoga.wind3.hub ([31.189.109.133]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de0967a0dsm16930322f8f.3.2026.10.15.01.17.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 01:17:32 -0700 (PDT) From: Andrea Parri To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: Andrea Parri , Kuniyuki Iwashima , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next v2] rtnetlink: comment the RCU waits in unregister paths Date: Thu, 15 Oct 2026 10:17:16 +0200 Message-ID: <20261015081723.404990-1-parri.andrea@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rtnl_unregister_all() and rtnl_af_unregister() wait for RCU readers before tearing down what those readers use, but do not say which readers they are waiting for. A missing wait is then easy to overlook: rtnl_link_unregister() lacked its synchronize_rcu() until commit 3b70edea393d ("rtnetlink: wait for RCU readers in rtnl_link_unregister()"). Add a comment to both waits, naming the readers each one waits for. Suggested-by: Eric Dumazet Link: https://lore.kernel.org/CAL4WiioFMQN4troVjQjCmE6Z9kwwb95SnoEupjD=PPSK6Q5f6w@mail.gmail.com Assisted-by: LLM Signed-off-by: Andrea Parri --- v2: - Drop the comments on synchronize_srcu(), its argument already names the readers (Kuniyuki) - Name rtnetlink_rcv_msg() and try_module_get() in the rtnl_unregister_all() comment (Kuniyuki) - Mention the rtnl_af_ops walkers that do not take ops->srcu in the rtnl_af_unregister() comment v1: https://lore.kernel.org/20261008124423.11543-1-parri.andrea@gmail.com net/core/rtnetlink.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 15bffafbf0a9c..d73dbc2c8ba0d 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -526,6 +526,9 @@ void rtnl_unregister_all(int protocol) } rtnl_unlock(); + /* Wait for rtnl_get_link() calls that rtnetlink_rcv_msg() makes + * under RCU, before try_module_get(). + */ synchronize_net(); kfree(tab); @@ -843,6 +846,9 @@ void rtnl_af_unregister(struct rtnl_af_ops *ops) list_del_rcu(&ops->list); spin_unlock(&rtnl_af_ops_lock); + /* Wait for rtnl_af_ops walkers that invoke callbacks without + * ops->srcu, and for rtnl_af_lookup() readers not yet holding it. + */ synchronize_rcu(); synchronize_srcu(&ops->srcu); cleanup_srcu_struct(&ops->srcu); -- 2.53.0