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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 D8238C433DF for ; Tue, 30 Jun 2020 20:22:33 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9E6AB20768 for ; Tue, 30 Jun 2020 20:22:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="jpa2yFjG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E6AB20768 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MHRB++by3uAE2VNI/WsgH4eulOJ50T7fGSTkPFxpYto=; b=jpa2yFjGFWXf0THIp0Uzb+FVc 8fi+bpaxQFcV7TALCquGKOPJzW0F3C2geSXkDUEMeTTGbbaQ8wgyUxMC9TTE9EhXVUiri/FjNpJ1g whXqi1TwpbkpoxIqZmxJ0kIhXM26nQffKCwVu4W047i/TXThtq3gxwS19NSIDeC5Xeb9VtEWEOJ/d XlNJjnWuUukFHjJgPjtBD+8nWYIdbTdQapUCpZqVqmBQNpQdPjskuQRxkCkfP8IJfni2CgHN+dR3h Dkxo2xKCzdCaQOHGiPt3ZHZpdZht6H+zE1ycVRiEU014OgUEN2MfK7UFwWrqeklY0L5rhS2uzZ9Aj KFsUIcWEA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqMkj-0000sn-PW; Tue, 30 Jun 2020 20:21:13 +0000 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 1jqMkd-0000sY-D6; Tue, 30 Jun 2020 20:21:07 +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 A75C130015A; Tue, 30 Jun 2020 22:20:59 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 850D8203A69CB; Tue, 30 Jun 2020 22:20:59 +0200 (CEST) Date: Tue, 30 Jun 2020 22:20:59 +0200 From: Peter Zijlstra To: Marco Elver Subject: Re: [PATCH 18/18] arm64: lto: Strengthen READ_ONCE() to acquire when CLANG_LTO=y Message-ID: <20200630202059.GE4817@hirez.programming.kicks-ass.net> References: <20200630173734.14057-1-will@kernel.org> <20200630173734.14057-19-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Android Kernel Team , Kees Cook , "Paul E. McKenney" , "Michael S. Tsirkin" , Catalin Marinas , Jason Wang , Nick Desaulniers , LKML , Josh Triplett , Ivan Kokshaysky , linux-arm-kernel@lists.infradead.org, Sami Tolvanen , linux-alpha@vger.kernel.org, Alan Stern , Matt Turner , virtualization@lists.linux-foundation.org, Will Deacon , Boqun Feng , Arnd Bergmann , Richard Henderson Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jun 30, 2020 at 09:47:30PM +0200, Marco Elver wrote: > I do wonder, though, if there is some way to make the compiler do > something better for us. Clearly, implementing real > memory_order_consume hasn't worked out until today. But maybe the > compiler could promote dependent loads to acquires if it recognizes it > lost dependencies during optimizations. Just thinking out loud, it > probably still has some weird corner case that will break. ;-) I'd be very hesitant to let the compiler upgrade the ordering for us, specifically because we're not using C11 crud and are using a lot of inline asm. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel