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,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 D2EDCC282D7 for ; Wed, 30 Jan 2019 19:46:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9CA7E21473 for ; Wed, 30 Jan 2019 19:46:50 +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="py3k+Gov" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387750AbfA3Tqt (ORCPT ); Wed, 30 Jan 2019 14:46:49 -0500 Received: from merlin.infradead.org ([205.233.59.134]:53558 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727890AbfA3Tqt (ORCPT ); Wed, 30 Jan 2019 14:46:49 -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=Uv2SC0YJQQTrRMnSUo4KBsvvFtdCsyHxX/IRQOxQH1I=; b=py3k+GovyvsVfSIiP3dJQq32U RgXTgaWdkec2q21E6hxG7+UssABn6sPfX5dFf002pXApjDX1dDOu28hRgoezvxLitXsAHHPpLdGSO scyOcoQV8CDRKDN8ZH8OqAViyHGeoR0FzjHJw9b+XOeE9CNQcqklxX3o+eWXRf6cr5NEkA2EeepEt 4xlaHRm6YEvpG7bHnDwjrEUnyW/VgdEsExNem7d6/kf++r1VXQudpSedIrShY23ZCiFmttHcHHYLV eV+R/X5zzBoooZGqVqPJfz1R4fDehhug8STOb6fnfflgU4DzZv8BqXb4PNsnj5T5NV61j/daweBFI /Jynst5Cg==; 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 1govom-00073I-I3; Wed, 30 Jan 2019 19:46:40 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 55E9A20423036; Wed, 30 Jan 2019 20:46:39 +0100 (CET) Date: Wed, 30 Jan 2019 20:46:39 +0100 From: Peter Zijlstra To: Alexei Starovoitov Cc: Alexei Starovoitov , 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 3/4] bpf: fix lockdep false positive in bpf_prog_register Message-ID: <20190130194639.GB3085@hirez.programming.kicks-ass.net> References: <20190130040458.2544340-1-ast@kernel.org> <20190130040458.2544340-4-ast@kernel.org> <20190130101058.GD2278@hirez.programming.kicks-ass.net> <20190130193241.4gkbc7zuo3m7r3ll@ast-mbp.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190130193241.4gkbc7zuo3m7r3ll@ast-mbp.dhcp.thefacebook.com> 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 Wed, Jan 30, 2019 at 11:32:43AM -0800, Alexei Starovoitov wrote: > On Wed, Jan 30, 2019 at 11:10:58AM +0100, Peter Zijlstra wrote: > > > > Why do you say this is not possible? All you need is 3 CPUs, one doing a > > CPU online, one doing a perf ioctl() and one doing that > > bpf_probe_register(). > > yeah. indeed. I'm impressed that lockdep figured it out > while I missed it manually looking through the code and stack traces. That's what it does :-)