Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754205AbbEMHib (ORCPT ); Wed, 13 May 2015 03:38:31 -0400 Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:48326 "EHLO e06smtp10.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753339AbbEMHi0 (ORCPT ); Wed, 13 May 2015 03:38:26 -0400 Date: Wed, 13 May 2015 09:38:12 +0200 From: David Hildenbrand To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, yang.shi@windriver.com, benh@kernel.crashing.org, paulus@samba.org, akpm@linux-foundation.org, heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, borntraeger@de.ibm.com, mst@redhat.com, tglx@linutronix.de, David.Laight@ACULAB.COM, hughd@google.com, hocko@suse.cz, ralf@linux-mips.org, herbert@gondor.apana.org.au, linux@arm.linux.org.uk, airlied@linux.ie, daniel.vetter@intel.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, peterz@infradead.org Subject: Re: [PATCH v1 11/15] arm/futex: UP futex_atomic_op_inuser() relies on disabled preemption Message-ID: <20150513093812.65fdac96@thinkpad-w530> In-Reply-To: <20150512190014.GD25464@linutronix.de> References: <1431359540-32227-1-git-send-email-dahi@linux.vnet.ibm.com> <1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com> <20150512190014.GD25464@linutronix.de> Organization: IBM Deutschland GmbH X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.27; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051307-0041-0000-0000-000004388B4C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 936 Lines: 30 > * David Hildenbrand | 2015-05-11 17:52:16 [+0200]: > > >The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely > >on disabled preemption to guarantee mutual exclusion. > > Yes, this is what the code looks like. It is more the requirement for > ldrex/strex opcodes which are ARMv6+ and so is SMP support (here). > Documentation wise you could replace CONFIG_SMP by > __LINUX_ARM_ARCH__ >= 6 > in a later patch if you like. This would be more in-sync with > arch/arm/include/asm/cmpxchg.h :) > > Sebastian Thanks, I'll include it in the next version. So I assume the cleanest thing to do would be: #if __LINUX_ARM_ARCH__ < 6 preempt_disable(); #endif David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/