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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 B7E3CC4338F for ; Thu, 5 Aug 2021 15:10:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A3CB60EEA for ; Thu, 5 Aug 2021 15:10:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241896AbhHEPKl (ORCPT ); Thu, 5 Aug 2021 11:10:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233201AbhHEPKk (ORCPT ); Thu, 5 Aug 2021 11:10:40 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 196D0C061765; Thu, 5 Aug 2021 08:10:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=eSJtsF6Jeti9fhWnHbLl2fELMn0F+2fN4MBTm3vWTW0=; b=MlcIUmoXpg52Stjx4LMJuW97mw C2qZUotjUrwxXQShT5OTm1MEIacvPBuJxY78NRoO/UUbmvLYE8ntiPRjgn8VPaXlQTYTFQbNIQ7Pr 9xeBsNOuh1g8ha+eJgwu76QV/UpoeEAhDbFFBznTYi8u9PETyyAsLNc3amnANgMXarEBdpcZTJJw4 Q0lghQDit4CRVN9CThoiSDTLPv2z2xs4f/sKCTBp5Hhjom9WncXuYqJaaEQ1YMETq48ssLN/w+897 +NohM/qzPW7fnt5D3c9O1ABDUxbx45gq8QRChsNADCGukjTEnDXYxuolSgMosWTnsM61I1TiyJou4 Td/0XmYQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBf0d-0065gm-6d; Thu, 05 Aug 2021 15:10:11 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D7B4830027B; Thu, 5 Aug 2021 17:10:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BC1A4299CE2A6; Thu, 5 Aug 2021 17:10:08 +0200 (CEST) Date: Thu, 5 Aug 2021 17:10:08 +0200 From: Peter Zijlstra To: Davidlohr Bueso Cc: Arnd Bergmann , Lukas Bulwahn , Michel Lespinasse , Andrew Morton , Mete Polat , Jesper Nilsson , David Woodhouse , Ingo Molnar , Randy Dunlap , kernel-janitors@vger.kernel.org, Linux Kernel Mailing List , Geert Uytterhoeven Subject: Re: [PATCH] rbtree: remove unneeded explicit alignment in struct rb_node Message-ID: References: <20210805133213.700-1-lukas.bulwahn@gmail.com> <50ad4c8b848bd371b4b42959167ef03d@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50ad4c8b848bd371b4b42959167ef03d@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 05, 2021 at 08:02:28AM -0700, Davidlohr Bueso wrote: > On 2021-08-05 07:02, Arnd Bergmann wrote: > > The revert would appear to change the alignment to 16 bits instead > > of 32 bits on m68k as well (not 8 bits as on cris), but I don't know if > > that > > can cause problems there. > > Yeah I tried this a while back and it broke m68k, so it was a no go: > > https://lore.kernel.org/lkml/CAMuHMdXeZvJ0X6Ah2CpLRoQJm+YhxAWBt-rUpxoyfOLTcHp+0g@mail.gmail.com/ I'm still thinking that any architecture that doesn't respect natural alignment is playing with fire. For giggles we should put a runtime alignment check in READ_ONCE() and see what goes *bang*.