Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933900Ab1CaKRD (ORCPT ); Thu, 31 Mar 2011 06:17:03 -0400 Received: from mprc.pku.edu.cn ([162.105.203.9]:44388 "EHLO mprc.pku.edu.cn" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933887Ab1CaKRA (ORCPT ); Thu, 31 Mar 2011 06:17:00 -0400 From: "Guan Xuetao" To: "'Arnd Bergmann'" , "'Thomas Gleixner'" Cc: "'Paul Mundt'" , , References: <01eb01cbeeb7$30390460$90ab0d20$@mprc.pku.edu.cn> <201103301417.20027.arnd@arndb.de> <201103301440.03479.arnd@arndb.de> In-Reply-To: <201103301440.03479.arnd@arndb.de> Subject: RE: [PATCH] unicore32 fix: remove arch-specific futex support Date: Thu, 31 Mar 2011 18:16:20 +0800 Message-ID: <004301cbef8c$b0bf0640$123d12c0$@mprc.pku.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQKI+b6m1CyJqXYj5hUyo+RnqBvTZgGkwykXAp/ha8wBh0wlqpKexHwg Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1289 Lines: 39 > -----Original Message----- > From: Arnd Bergmann [mailto:arnd@arndb.de] > Sent: Wednesday, March 30, 2011 8:40 PM > To: Thomas Gleixner > Cc: Guan Xuetao; Paul Mundt; linux-kernel@vger.kernel.org; linux-arch@vger.kernel.org > Subject: Re: [PATCH] unicore32 fix: remove arch-specific futex support > > On Wednesday 30 March 2011, Thomas Gleixner wrote: > > The problem is that you need cmpxchg in user space as well. > > > > ARM does this with some syscall magic for machines which do not have > > cmpxchg. > > Ah, right. I wonder how sh does it. > > I also remember that the original unicore32 ABI had support for a cmpxchg > system call, but that was removed with the move to the generic syscall > table. > > It is of course possible to add it back using the __NR_arch_specific_syscall > entry point. > > Arnd For cmpxchg, we have both system call and kuser_cmpxchg supports in old abi which are similar to arm. The performance of system call version is too poor, so it could be only used for test. Thanks & Regards Guan Xuetao -- 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/