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 8E121C43612 for ; Mon, 17 Dec 2018 22:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BFF221473 for ; Mon, 17 Dec 2018 22:50:32 +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="0w7whLyp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732211AbeLQWub (ORCPT ); Mon, 17 Dec 2018 17:50:31 -0500 Received: from merlin.infradead.org ([205.233.59.134]:59112 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727342AbeLQWua (ORCPT ); Mon, 17 Dec 2018 17:50:30 -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=ewyNVfIQur5dYaPnBPCaCuzQ2dHgrMZzNkkb6MCSIxQ=; b=0w7whLyppnyCzu1paF1B2/tuq sA9+Sqikd5vWwFnDWR6iTSlLQwO3xClbfLeViWsViFel2HtWeFUbdkX+OdTSFBheWaGf6Wcg55qEI sq0Zr/ofhEJFTzkK+YpAv+fBZeYpXomyffG+Q6exz9k4Ywysh7gCYvzt5og9mtSjaULwsWmO7BOFZ ZIKvC7KwbHy8SmI2maS7J3M/YopkkNB5wbJ00NUzc64FV3FMTb6yB8DKCsfx74T9cRxKvXy8AvzEB 0LF/RBXArU814VKuP6Vdy07oQkmeQccHkrTRBKoh18/2DEJQ0BDsQgTgjOIJUiNZr1e0KTFbfCYLZ CTCKHm87Q==; 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 1gZ1iP-0004LK-8x; Mon, 17 Dec 2018 22:50:21 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 16A9F20276AAC; Mon, 17 Dec 2018 23:50:20 +0100 (CET) Date: Mon, 17 Dec 2018 23:50:20 +0100 From: Peter Zijlstra To: Arnd Bergmann Cc: Nicolas Pitre , Andi Kleen , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Paul McKenney , Will Deacon , Ingo Molnar , Thomas Gleixner Subject: Re: [PATCH 0/7] ARM: hacks for link-time optimization Message-ID: <20181217225020.GA16520@hirez.programming.kicks-ass.net> References: <20180220215954.4092811-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180220215954.4092811-1-arnd@arndb.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 20, 2018 at 10:59:47PM +0100, Arnd Bergmann wrote: > Hi Nico, all, > > I was playing with ARM link-time optimization handling earlier this > month, and eventually got it to build cleanly with randconfig kernels, > but ended up with a lot of ugly hacks to actually pull it off. How are we dealing with the fact that LTO can break RCU in very subtle and scary ways? Do we have a compiler guy on board that has given us a compiler switch that kills that optimization (and thereby guarantees that behaviour for future compilers etc..) ? Also see the thread here: https://lkml.kernel.org/r/20171116115810.GH9361@arm.com (and yes, this is a fine example of how lore sucks for reading email)