From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:54564 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932436AbeGIOLP (ORCPT ); Mon, 9 Jul 2018 10:11:15 -0400 Date: Mon, 9 Jul 2018 16:10:56 +0200 From: Peter Zijlstra Subject: Re: [PATCH v3] devres: Explicitly align datai[] to 64-bit Message-ID: <20180709141056.GR2512@hirez.programming.kicks-ass.net> References: <20180709134550.29541-1-abrodkin@synopsys.com> <20180709140717.GR2476@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180709140717.GR2476@hirez.programming.kicks-ass.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Alexey Brodkin Cc: linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org, Greg Kroah-Hartman , Geert Uytterhoeven , David Laight , Thomas Gleixner , Will Deacon , Greg KH , stable@vger.kernel.org Message-ID: <20180709141056.f6RoRcybLtYI0w0yxbUBjppOGy8D09wBk4dt9d7fPJg@z> On Mon, Jul 09, 2018 at 04:07:17PM +0200, Peter Zijlstra wrote: > On Mon, Jul 09, 2018 at 04:45:50PM +0300, Alexey Brodkin wrote: > > --- a/drivers/base/devres.c > > +++ b/drivers/base/devres.c > > @@ -24,8 +24,12 @@ struct devres_node { > > > > struct devres { > > struct devres_node node; > > - /* -- 3 pointers */ > > - unsigned long long data[]; /* guarantee ull alignment */ > > + /* > > + * data[] must be 64 bit aligned even on 32 bit architectures > > + * because it might be accessed by instructions that require > > + * aligned memory arguments such as atomic64_t. > > + */ > > + u8 __aligned(8) data[]; > > }; > > Seeing that this ends up in a semi generic allocation thing, I don't > feel this should be different from ARCH_KMALLOC_MINALIGN. In fact, since alloc_dr() uses kmalloc() to allocate the entire thing, it is impossible to guarantee a larger alignment than kmalloc does.