From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACCA5C33CAF for ; Thu, 23 Jan 2020 17:10:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 829AB206D4 for ; Thu, 23 Jan 2020 17:10:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Q+0rToUt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728984AbgAWRKg (ORCPT ); Thu, 23 Jan 2020 12:10:36 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:38688 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726792AbgAWRKf (ORCPT ); Thu, 23 Jan 2020 12:10:35 -0500 Received: by mail-pf1-f196.google.com with SMTP id x185so1827376pfc.5; Thu, 23 Jan 2020 09:10:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=dwJyEOh0uaEFN8hvYa0cHHjOAWxYFsxMT7IvzzrReQI=; b=Q+0rToUtIGpg7FyoIxscNn0/RvwL4rrUkiWJ2n9IN6HO9n6C92QHkv3PBUv041aJYu mhN6B7xMAbD4MEjZ1KErr52A1355A4yLo/jrh+8OMVJFVMi9N0uLTD/xzth/Z5XXNuiH pj+n1GxZR1N3JjT3luH+GnzF2OUyJBJmFx5VrQKzi9Ku6ijV1k5R+Y/ABzn0msWOLa+S AQacTj99pd98x2EEzNLKNNTDAMGCRkI+Gv35q69dZGeHCyFII22FwqTtXv7huPFQjZyg jdx/c+WMlH/0fkCS9kzBPsMPYl9tBQWnKxG6GkXVV0lrMwCKApfi2RA6gkvJfIEXwxRF Q0wQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=dwJyEOh0uaEFN8hvYa0cHHjOAWxYFsxMT7IvzzrReQI=; b=IfVfTarMOEKIxuHAZY9w7aVD0yPfbQRXh7wbNXIWR4UCgHDCLG+nsSwovf1gkNNQpE qelNpfBlzJNHSHVW4ktpWtlmJiuiotJk9Za783xvE5QGFPNOQB8OXa9D0UQEIjoRN/Z+ wrcKvDbjYA8AfCU0vheiJPtsLom+8OLGzdUT7Ebyd20EUoVtnCfTvh8DuUJ3Bm6B7584 Ge1LYWB8//bvmEGbV11hlU0A1qVoU+XD1KMoFZjljzoJpQUCZ+44nTLYr/p+gsajvFZG RWkRVKmQ3zfcehcqvd1ZgaeqBMm2LGpA8wrovtJLyaW5dQSjZrx4lTaeYoJ+m+JXBHE5 fR/A== X-Gm-Message-State: APjAAAUHe+WnyxfkUhrSUOCybaVW5m2+WcxWTOSu6NHc4/lng2h7cwQV VfwX4E/km9YO4nT+nS0V7sE= X-Google-Smtp-Source: APXvYqzsPgVtLCqC7XrdMEUUv9WDoR31GK4BL6XC9b4+BRA3q1+quhAdIpoKGpQQi5I2/2vFliqsPg== X-Received: by 2002:a63:780d:: with SMTP id t13mr4718336pgc.82.1579799434594; Thu, 23 Jan 2020 09:10:34 -0800 (PST) Received: from workstation-portable ([103.211.17.138]) by smtp.gmail.com with ESMTPSA id bo19sm3405156pjb.25.2020.01.23.09.10.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jan 2020 09:10:34 -0800 (PST) Date: Thu, 23 Jan 2020 22:40:25 +0530 From: Amol Grover To: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= Cc: Jesper Dangaard Brouer , Alexei Starovoitov , Daniel Borkmann , "David S . Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Joel Fernandes , Madhuparna Bhowmik , "Paul E . McKenney" Subject: Re: [PATCH] bpf: devmap: Pass lockdep expression to RCU lists Message-ID: <20200123171025.GB4484@workstation-portable> References: <20200123120437.26506-1-frextrite@gmail.com> <20200123143725.036140e7@carbon> <87a76e9tn8.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87a76e9tn8.fsf@toke.dk> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jan 23, 2020 at 02:42:03PM +0100, Toke Høiland-Jørgensen wrote: > Jesper Dangaard Brouer writes: > > > On Thu, 23 Jan 2020 17:34:38 +0530 > > Amol Grover wrote: > > > >> head is traversed using hlist_for_each_entry_rcu outside an > >> RCU read-side critical section but under the protection > >> of dtab->index_lock. > > > > We do hold the lock in update and delete cases, but not in the lookup > > cases. Is it then still okay to add the lockdep_is_held() annotation? > > I concluded 'yes' from the comment on hlist_for_each_entry_rcu(): > > The lockdep condition gets passed to this: > > #define __list_check_rcu(dummy, cond, extra...) \ > ({ \ > check_arg_count_one(extra); \ > RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(), \ > "RCU-list traversed in non-reader section!"); \ > }) > > > so that seems fine :) > Yes, adding a lockdep expression will be okay. This is because an implicit check is done to check if list_for_each_entry_rcu() is traversed under RCU read-side critical section. In case the traversal is outside RCU read-side critical section, the lockdep expression makes sure the traversal is done under the mentioned lock. Thanks Amol > -Toke >