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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham 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 0DCBFC282D7 for ; Wed, 30 Jan 2019 10:21:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D322120833 for ; Wed, 30 Jan 2019 10:21:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="t9n0OVzP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730470AbfA3KVd (ORCPT ); Wed, 30 Jan 2019 05:21:33 -0500 Received: from merlin.infradead.org ([205.233.59.134]:46914 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbfA3KVd (ORCPT ); Wed, 30 Jan 2019 05:21:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=USBjDrpG8KHMy+xU8WG34N+jcHTBB/pbiDFax8nn2GM=; b=t9n0OVzPh+bmb7Xc+ZRpiWFNo Ya9+HiPjWxqeXvu5D8bjDyK3i+aDTtCyRIbtFcWqW7k0mdujK2DEul/C7KN4fRtMETnFDqJCUwtGH zB8FsyYDaUxabUrHUIpSkQW8OD9XJmjgLBQalbm/w65N98CdL2yL+A0KvMgDuMOrwhTyBOB3PRjhO QtGmnajouP+vJ85xqQKVerZRri3TFBbe0vI3ddti4DQELZ87hIUmT+e5t49JI6ZDVdM4FyUMyEtoA uEzmWSno0fe575WvZ+fGsAyBxmv2gI5X7YKiknv8RY0xdGepF+qlY/JkxlfzZTAywbwmUgWQqugjG b2Q7vmZuw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gomzn-00081B-CQ; Wed, 30 Jan 2019 10:21:27 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2BA39202C6BEA; Wed, 30 Jan 2019 11:21:26 +0100 (CET) Date: Wed, 30 Jan 2019 11:21:26 +0100 From: Peter Zijlstra To: Alexei Starovoitov Cc: davem@davemloft.net, daniel@iogearbox.net, edumazet@google.com, jannh@google.com, netdev@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH bpf-next 1/4] bpf: fix lockdep false positive in percpu_freelist Message-ID: <20190130102126.GF2278@hirez.programming.kicks-ass.net> References: <20190130040458.2544340-1-ast@kernel.org> <20190130040458.2544340-2-ast@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190130040458.2544340-2-ast@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Jan 29, 2019 at 08:04:55PM -0800, Alexei Starovoitov wrote: > > It has been explained that is a false positive here: > https://lkml.org/lkml/2018/7/25/756 Please, no external references like that. The best option is to fully include the explanation here so that a future software archeology student (note, this might be yourself in a years time) can find all relevant information in the git history. Or, if you _really_ _really_ have to refer to external sources, use: https://lkml.kernel.org/r/${msg_id} which is a controlled URL and can be made to point to any archive (currently, and sadly, lore.kernel.org). Also, since it includes the whole msg_id, people can trivially find the email in their local archive. While I agree that lkml.org is a _MUCH_ saner interface than lore (which causes eye and brain cancer for just looking at it), it is a _really_ flaky website and the url contains no clues for finding it in the local archive. > Recap: > - stackmap uses pcpu_freelist > - The lock in pcpu_freelist is a percpu lock > - stackmap is only used by tracing bpf_prog > - A tracing bpf_prog cannot be run if another bpf_prog > has already been running (ensured by the percpu bpf_prog_active counter).