Received: by 2002:a05:6a10:a852:0:0:0:0 with SMTP id d18csp636482pxy; Wed, 5 May 2021 10:02:05 -0700 (PDT) X-Google-Smtp-Source: ABdhPJws45Qlh6iBzqehNq7bATvvwU3q2wBjSkb0bzsEfeKBbgv/r3Sjz7CF39vK7GySLrBzylll X-Received: by 2002:a17:90a:520f:: with SMTP id v15mr12545520pjh.205.1620234125545; Wed, 05 May 2021 10:02:05 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1620234125; cv=none; d=google.com; s=arc-20160816; b=nS/X47qOFFufQHokZJnvSdpx/tO7441UDWpTcNe94JASt+/StdY4w75VXnyZkaLCWQ NXW2uszWSNCPJ7I3Oi1WCiYhLaFHtGZ1cxnFpU+/khNKsXEdXf6EuuQgSOT3u7+z6Jee VnGtI1EJlxnRQkYlViLK5Uh1cMaSy6/2aUCC+FdnEZ/bh04rGVMmUFySqrN2UK8+B2Gb RmNDGo88fquOR4jsPc1jpYEJ5Mx1qOz8ewZeGA8cTUqnbb7Ma4IS7v3U0bcf93TjYNiO XV9sk2bFTQ/xKtAk1DmcRa6LZMH88tlGSCJchUAt0QRQ+Pl2KQ4Mb/UBM4a/MFqfncQt 0mOg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-language:content-transfer-encoding :in-reply-to:mime-version:user-agent:date:message-id:from:references :cc:to:subject:ironport-sdr:ironport-sdr; bh=kzkRIgUptzJqwNUslDPBxZ4VNpczYBBaf3LvXGHsXxo=; b=lFZaCtNqUa26ugFPhfiW7J5WzNGtVysmnyByR7s57me+zTB2nmP7xWvPa8+uK4pBUP axZQ7GkG6iLEGBeJbtBnntoaYRkUhvw884fWGMOfJzguNMi5Ps0TmMz8Fjjh4X/LxFrK 980FIxfSKga1ON17KDvXdIyYZnLWBuhliq5OUMprrEMUvu+QfjF6EHWQOA8SXEGGH0dW D/ZcTJN3GWevmnDovkhyf4zmGZXpfGAnFrv4dTj3hrDG41hR6YkneBwdPyEXRLNTD+LJ 7lFZnS300bF27cnyC0CN7P7FumfLk8VdgNJps7NDh/5SBY1zCBzw1uHEduo0v/kSM0BF +2cQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id t17si7124184pgm.289.2021.05.05.10.01.52; Wed, 05 May 2021 10:02:05 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237322AbhEEQ7u (ORCPT + 99 others); Wed, 5 May 2021 12:59:50 -0400 Received: from mga06.intel.com ([134.134.136.31]:17204 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236788AbhEEQuk (ORCPT ); Wed, 5 May 2021 12:50:40 -0400 IronPort-SDR: gi1n5t0nY4g1qzPaixI/H3i4gMiaKfLX+O2MPkwpuIDi7XDniZcRgsMqywulBDr4wWgYdVkGhb +VaLOOAy0VgQ== X-IronPort-AV: E=McAfee;i="6200,9189,9975"; a="259532499" X-IronPort-AV: E=Sophos;i="5.82,276,1613462400"; d="scan'208";a="259532499" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2021 09:48:59 -0700 IronPort-SDR: Yi0pqyiLHdZUJPiYaOEO9OzZCRUx5JnU+c6yPbfqsCoxO4w09k7+O5Tndp3LyQFURANRYVzkjF ZUTH/AGmpyXA== X-IronPort-AV: E=Sophos;i="5.82,276,1613462400"; d="scan'208";a="433911466" Received: from akleen-mobl1.amr.corp.intel.com (HELO [10.209.54.13]) ([10.209.54.13]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2021 09:48:59 -0700 Subject: Re: [PATCH] sched: Work around undefined behavior in sched class checking To: Nick Desaulniers Cc: Florian Weimer , Peter Zijlstra , LKML , Andi Kleen , linux-toolchains@vger.kernel.org References: <20210505033945.1282851-1-ak@linux.intel.com> <875yzxh8j8.fsf@oldenburg.str.redhat.com> <20210505143916.GS4032392@tassilo.jf.intel.com> From: Andi Kleen Message-ID: Date: Wed, 5 May 2021 09:48:58 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/5/2021 9:41 AM, Nick Desaulniers wrote: > On Wed, May 5, 2021 at 7:39 AM Andi Kleen wrote: >>> Would you please provide a >>> minimal test case? >> You can only reproduce it with a LTO build because it needs knowledge >> between different translation units for this specific case. >> >> But gcc will totally do the optimization even without LTO if it can >> prove the same inside a single TU. > It would be helpful to isolate a test case that doesn't rely on LTO, > if possible. Like I wrote earlier we used to see it all the time in __pa_symbol before it used RELOC_HIDE. I bet if you make RELOC_HIDE a nop you'll see multiple instances. But not sure why you want a test case? -Andi