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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 52BA4C433DF for ; Mon, 6 Jul 2020 19:40:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D89520675 for ; Mon, 6 Jul 2020 19:40:26 +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="BeTQRyoG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726540AbgGFTkZ (ORCPT ); Mon, 6 Jul 2020 15:40:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725860AbgGFTkZ (ORCPT ); Mon, 6 Jul 2020 15:40:25 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E687C061755; Mon, 6 Jul 2020 12:40:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=Fga2epNTXBelXbYkbTxROQdchUloEASZKoCcJ/iKrWw=; b=BeTQRyoGVX7klkBfy71IhIii42 JLJVPvYdGVws5AyPO2wATPQh812LcOHjFg8RqbL8QgCaxHK+B103YXboryKFzbnforwfw09tNatE9 Ijvwo8PiAqBc+pqw5sDe87w5LOI2SYN6KwrLb1mF4UNVYiAxzyYRJj/nUVEy5N9Th6O/tYCF8VpZV yC2XlC+u2k195dE9l9ZVM2DO+equSQoon5zhP1iEjupkjTXqD4be/tJ9YsR2I1ClBCDJd+yYpIZXF Q6+cIuj+PAzHD6t30ZZbYPyuTxPG3nfJprRPcGf3KxUTK93dlpHy3vdg6mTpTVbfsaduXM8c65F50 6jIUEBlQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsWyN-0001u4-QE; Mon, 06 Jul 2020 19:40:16 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id D9A28980DD2; Mon, 6 Jul 2020 21:40:12 +0200 (CEST) Date: Mon, 6 Jul 2020 21:40:12 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Marco Elver , Nick Desaulniers , Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , linux-pci@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200706194012.GA5523@worktop.programming.kicks-ass.net> References: <20200701140654.GL9247@paulmck-ThinkPad-P72> <20200701150512.GH4817@hirez.programming.kicks-ass.net> <20200701160338.GN9247@paulmck-ThinkPad-P72> <20200702082040.GB4781@hirez.programming.kicks-ass.net> <20200702175948.GV9247@paulmck-ThinkPad-P72> <20200703131330.GX4800@hirez.programming.kicks-ass.net> <20200703144228.GF9247@paulmck-ThinkPad-P72> <20200706162633.GA13288@paulmck-ThinkPad-P72> <20200706182926.GH4800@hirez.programming.kicks-ass.net> <20200706183933.GE9247@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706183933.GE9247@paulmck-ThinkPad-P72> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Jul 06, 2020 at 11:39:33AM -0700, Paul E. McKenney wrote: > On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote: > > On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote: > > If they do not consider their Linux OS running correctly :-) > > Many of them really do not care at all. In fact, some would consider > Linux failing to run as an added bonus. This I think is why we have compiler people in the thread that care a lot more. > > > Nevertheless, yes, control dependencies also need attention. > > > > Today I added one more \o/ > > Just make sure you continually check to make sure that compilers > don't break it, along with the others you have added. ;-) There's: kernel/locking/mcs_spinlock.h: smp_cond_load_acquire(l, VAL); \ kernel/sched/core.c: smp_cond_load_acquire(&p->on_cpu, !VAL); kernel/smp.c: smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); arch/x86/kernel/alternative.c: atomic_cond_read_acquire(&desc.refs, !VAL); kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, VAL == _QW_WAITING); kernel/locking/qspinlock.c: atomic_cond_read_acquire(&lock->val, !(VAL & _Q_LOCKED_MASK)); kernel/locking/qspinlock.c: val = atomic_cond_read_acquire(&lock->val, !(VAL & _Q_LOCKED_PENDING_MASK)); include/linux/refcount.h: smp_acquire__after_ctrl_dep(); ipc/mqueue.c: smp_acquire__after_ctrl_dep(); ipc/msg.c: smp_acquire__after_ctrl_dep(); ipc/sem.c: smp_acquire__after_ctrl_dep(); kernel/locking/rwsem.c: smp_acquire__after_ctrl_dep(); kernel/sched/core.c: smp_acquire__after_ctrl_dep(); kernel/events/ring_buffer.c:__perf_output_begin() And I'm fairly sure I'm forgetting some... One could argue there's too many of them to check already. Both GCC and CLANG had better think about it.