From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754698AbXLBLfg (ORCPT ); Sun, 2 Dec 2007 06:35:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752225AbXLBLf1 (ORCPT ); Sun, 2 Dec 2007 06:35:27 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:34397 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752045AbXLBLf0 (ORCPT ); Sun, 2 Dec 2007 06:35:26 -0500 Date: Sun, 2 Dec 2007 12:36:09 +0100 From: Pavel Machek To: David Brownell Cc: rtc-linux@googlegroups.com, kernel list , Alessandro Zummo Subject: Re: RTC wakealarm write-only, still has 644 permissions Message-ID: <20071202113609.GA1796@elf.ucw.cz> References: <20070920103225.GA4410@elf.ucw.cz> <200711291010.12707.david-b@pacbell.net> <20071130203544.GB1677@elf.ucw.cz> <200711301310.40360.david-b@pacbell.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200711301310.40360.david-b@pacbell.net> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > It's not an issue of accidental writes, it's an issue of there being > > > no other synchronization for setting those alarms. Remember that both > > > RTC_WKALM_SET and RTC_ALM_SET ioctls can set that same alarm, and so > > > could a different userspace activity ... > > > > We have 3 interfaces to one hardware resource. I do not think kernel > > should try to arbitrate it here. There's just one alarm clock with > > three interfaces. > > Having three interfaces is bad enough ... ensuring that none of > them can ever be used safely would be stupid. They can be used safely. You just have to pick one and stay with it. (And no, no-clobber hack does not help here. Or do you have specific application where no-clobber hack helps?) Anyway, with wildcarded dates, no-clobber is a problem -- because you need to kill the alarm after you waken up, or it will repeat. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html