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 8247CC43387 for ; Mon, 17 Dec 2018 22:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DD96217D9 for ; Mon, 17 Dec 2018 22:35:44 +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="YYjqK69n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731629AbeLQWfn (ORCPT ); Mon, 17 Dec 2018 17:35:43 -0500 Received: from merlin.infradead.org ([205.233.59.134]:59062 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727597AbeLQWfm (ORCPT ); Mon, 17 Dec 2018 17:35:42 -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=HJfsx6MFuQ3SfKsmFk+Dsj/k9mm//Ws87sbYqWOQO0s=; b=YYjqK69nkK2VzgMYFZfnRK/TL bKbLEH3LqEba+PjhTU8Hvj/UexE0NpmXfp5KvCPd1bsgC08QTJyC5jYUpd4Sdd5ATb3bkUmZYtg3E NR0NwkNrZK7wZGcnYUezkfJnEyzQoXm0LIRvSYYJLj7y+nLgzQqx6lNpwQwIoNkOdorXBtc8wkptA tq9MHznfF7wGUWwSYVPeVoo8ocRwZ/sgZHLvcL1Sb9iVbnUQqkJo8WYQNJe/XI0Dp6t4ZOS5Px9OU ogueJ6wlgDpgWbv+VHIQFkEn5Pq6PHXYRq3qn+NlpePfPa0SqZAIkokKnpIPzZ6v2meoc+AazGrxB xPWkYH66A==; 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 1gZ1Tz-0004Ir-6S; Mon, 17 Dec 2018 22:35:27 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8B0F320276ABC; Mon, 17 Dec 2018 23:35:24 +0100 (CET) Date: Mon, 17 Dec 2018 23:35:24 +0100 From: Peter Zijlstra To: Andi Kleen Cc: Josh Poimboeuf , Arnd Bergmann , Linux Kernel Mailing List , the arch/x86 maintainers , Steven Rostedt , Miroslav Benes Subject: Re: objtool warnings for kernel/trace/trace_selftest_dynamic.o Message-ID: <20181217223524.GH2218@hirez.programming.kicks-ass.net> References: <20181217173900.ygifx7khwmzn2gv2@treble> <20181217180434.GS25620@tassilo.jf.intel.com> <20181217181638.dfexg6mkmbfyzfli@treble> <20181217192938.GF2218@hirez.programming.kicks-ass.net> <20181217205535.GT25620@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181217205535.GT25620@tassilo.jf.intel.com> 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 Mon, Dec 17, 2018 at 12:55:35PM -0800, Andi Kleen wrote: > On Mon, Dec 17, 2018 at 08:29:38PM +0100, Peter Zijlstra wrote: > > When/if we get the LTO trainwreck sorted -- which very much includes > > getting that memory-order-consume fixed -- we can revisit all that. > > What do you mean? I'm not aware of any LTO problems with memory-order-consume? The compiler is basically allowed to break RCU (and anything else that depends on read-read dependencies). LTO makes it _far_ more likely this happens. We need guarantees (and possible switches) from the compiler folks that this will not happen before I'll retract my NAK from any LTO enabling.