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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 21A94C433E0 for ; Fri, 22 May 2020 09:44:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7FB22085B for ; Fri, 22 May 2020 09:44:46 +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="2Mxc8VJz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729366AbgEVJoq (ORCPT ); Fri, 22 May 2020 05:44:46 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40512 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728212AbgEVJop (ORCPT ); Fri, 22 May 2020 05:44:45 -0400 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; bh=GOPKud88OPaH4A20/+O8fxq1AaAngE7PqgDEZCOAn3I=; b=2Mxc8VJzybe5xRTMJ8Rxntxzng KlPBX7vn55ZvUFsiPEORsC2YKopZVg/ZPKl6PRF7/vcFjTqg8jW2z91stWvSncS3qE8I6ZGQJivSs FSdCwyRo3nUmEvUKBk46BTTGNYFNC3QgvTgMwoWWPFXobrzkeEOBtpjYC2TafAwcY0Z8XdHVPUjVx vaSafW2HHgLwqSDrv6ZRc3dYXl0gpdkI3/0BXoghNyxuNmnKRj476RqNZQKCY+jJ3fcM+r2Jr6ffZ WU4qJxwdAf/U4T+fjYggEPlGcGuNphhv/hX6VCLSYs74cZsgPdj2TVws/wokke/agGYZpuPpi8ZmM y8RKxa2g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jc4Dp-0005Dq-RF; Fri, 22 May 2020 09:44:10 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 07A1C306089; Fri, 22 May 2020 11:44:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E2B9A2B7348E8; Fri, 22 May 2020 11:44:07 +0200 (CEST) Date: Fri, 22 May 2020 11:44:07 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com, will@kernel.org, boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com, dlustig@nvidia.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, andriin@fb.com Subject: Re: Some -serious- BPF-related litmus tests Message-ID: <20200522094407.GK325280@hirez.programming.kicks-ass.net> References: <20200522003850.GA32698@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200522003850.GA32698@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2020 at 05:38:50PM -0700, Paul E. McKenney wrote: > Hello! > > Just wanted to call your attention to some pretty cool and pretty serious > litmus tests that Andrii did as part of his BPF ring-buffer work: > > https://lore.kernel.org/bpf/20200517195727.279322-3-andriin@fb.com/ > > Thoughts? I find: smp_wmb() smp_store_release() a _very_ weird construct. What is that supposed to even do?