Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 4 Apr 2002 15:30:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 4 Apr 2002 15:30:21 -0500 Received: from d12lmsgate-3.de.ibm.com ([195.212.91.201]:59037 "EHLO d12lmsgate-3.de.ibm.com") by vger.kernel.org with ESMTP id ; Thu, 4 Apr 2002 15:30:09 -0500 Importance: Normal Sensitivity: Subject: Re: Changes in s390x uaccess.h in 2.4.17+ To: zaitcev@redhat.com Cc: linux-kernel@vger.kernel.org, "Martin Schwidefsky" X-Mailer: Lotus Notes Release 5.0.3 (Intl) 21 March 2000 Message-ID: From: "Ulrich Weigand" Date: Thu, 4 Apr 2002 22:29:58 +0200 X-MIMETrack: Serialize by Router on D12ML028/12/M/IBM(Release 5.0.9a |January 7, 2002) at 04/04/2002 22:30:01 MIME-Version: 1.0 Content-type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pete Zaitcev wrote: >The 2.4.17 patch comes with a change to uaccess.h, which >contains the following: > >- * These functions have a non-standard call interface >+ * These functions have standard call interface > >Does it look familiar to anyone? The change is in Marcelo's >tree now, but I am curious what it actually does. This is just a minor optimization. The old code used to have the core of __copy_to_user_asm etc. inline, and only the exception fixup code in lib (__copy_to_user_fixup). The point of this was to save the cost of a function call for the default case. However, because of various reasons (tedious argument reloading, register pressure, code size) this 'optimization' turned out to be actually worse than just a plain function call, so we threw it out. The new code simply implements __copy_to_user_asm completely in lib. >The 2.4.17 patch readme says "This patch contains the current >recommended kernel 2.4.7 code base (up to 2002-01-21), >adapted to kernel 2.4.17.", but I cannot find this change >in any published 2.4.7 patches. I am pretty sure there must >be a good reason for the change, and it's interesting to >know what it is. The 2.4.17 patch also contains a number of minor cleanups that should not cause any noticeable difference in behaviour, like this one. We did not find it worthwhile to backport this to 2.4.7; we usually do that only for bugfixes. Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand Linux for S/390 Design & Development IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen Phone: +49-7031/16-3727 --- Email: Ulrich.Weigand@de.ibm.com - 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/