From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754932AbbDTQOH (ORCPT ); Mon, 20 Apr 2015 12:14:07 -0400 Received: from foss.arm.com ([217.140.101.70]:44862 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753321AbbDTQOB (ORCPT ); Mon, 20 Apr 2015 12:14:01 -0400 Date: Mon, 20 Apr 2015 17:13:57 +0100 From: Will Deacon To: Linus Torvalds Cc: Andrey Ryabinin , Catalin Marinas , "Paul E. McKenney" , Peter Zijlstra , "linux-arm-kernel@lists.infradead.org" , Linux Kernel Mailing List Subject: Re: [PATCH] arm64: Implement 1-,2- byte smp_load_acquire and smp_store_release Message-ID: <20150420161357.GE1504@arm.com> References: <1429544753-4120-1-git-send-email-a.ryabinin@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 20, 2015 at 05:08:37PM +0100, Linus Torvalds wrote: > On Mon, Apr 20, 2015 at 8:45 AM, Andrey Ryabinin wrote: > > > > Commit 8053871d0f7f ("smp: Fix smp_call_function_single_async() locking") > > started to use smp_load_acquire() to load 2-bytes csd->flags. > > That crashes arm64 kernel during the boot. > > Ahh. I don't disagree with your patch, but we should just make > csd->flags be an "int" regardless of this issue. > > There is absolutely no reason to try to use 16-bit words. It doesn't > save us any space (alignment), and it's just a *bad* idea to depend on > any kind of atomicity of 16-bit entities. Bytes, yes. Words, yes. But > 16-bit half-words? There's no point. > > So I'll make it "unsigned int" instead of "u16". > > But as said, the ARM64 patch definitely is a good idea regardless. Sounds good to me and means I can leave the pull for a day or two to see if any other arm64 fixes queue up. Will