Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762916AbXFED71 (ORCPT ); Mon, 4 Jun 2007 23:59:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760367AbXFED7T (ORCPT ); Mon, 4 Jun 2007 23:59:19 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:2723 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759902AbXFED7S (ORCPT ); Mon, 4 Jun 2007 23:59:18 -0400 Date: Tue, 5 Jun 2007 04:59:03 +0100 From: Russell King To: Martin Peschke Cc: Andrew Morton , Adrian Bunk , linux-kernel@vger.kernel.org Subject: Re: 2.6.22-rc3-mm1: __attribute__((weak)) considered harmful Message-ID: <20070605035903.GD9045@flint.arm.linux.org.uk> Mail-Followup-To: Martin Peschke , Andrew Morton , Adrian Bunk , linux-kernel@vger.kernel.org References: <20070530235823.793f00d9.akpm@linux-foundation.org> <20070602171425.GG5500@stusta.de> <20070604142212.c0b68d6a.akpm@linux-foundation.org> <4664A5C6.7020004@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4664A5C6.7020004@de.ibm.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1710 Lines: 39 On Tue, Jun 05, 2007 at 01:52:38AM +0200, Martin Peschke wrote: > Andrew Morton wrote: > >On Sat, 2 Jun 2007 19:14:25 +0200 > >Adrian Bunk wrote: > > > >>statistics-infrastructure-make-printk_clock-a-generic-kernel-wide-nsec-resolution.patch > >>shows why __attribute__((weak)) is harmful because you don't see if a > >>required non-weak implemtation is missing: > >> > >>In this case, the weak printk_clock() was renamed to timestamp_clock(), > >>but the ARM and i386 implementations weren't renamed... > >> > > > >printk_clock() is sched_clock() in disguise, and I'm not sure that making > >sched_clock() more widely available in this fashion is something that we > >want to do anyway. Note that sched_clock() can not be used early on ARM; it might want to access MMIO which is not accessible until later in setup_arch(). This is why ARM's printk_clock() divorces itself from sched_clock(). > As to timestamp_clock(): its useful for statistics, but still a minor > feature. It would be unfortuante if that was the stumbling block for my > patches. Am I right that the fix for the issue pointed at by Adrian is to > rename those two occurrences of printk_clock()? Do you want me to submit a > patch? If it's ends up being based upon sched_clock() instead of printk_clock() on ARM then it'll break stuff horribly (== non-bootable kernels.) -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - 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/