Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758378AbZFCO6W (ORCPT ); Wed, 3 Jun 2009 10:58:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753954AbZFCO6O (ORCPT ); Wed, 3 Jun 2009 10:58:14 -0400 Received: from fifo99.com ([67.223.236.141]:56958 "EHLO fifo99.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753587AbZFCO6N (ORCPT ); Wed, 3 Jun 2009 10:58:13 -0400 Subject: Re: [PATCH] sched: sched_clock() clocksource handling. From: Daniel Walker To: Paul Mundt Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Linus Walleij , Andrew Victor , Haavard Skinnemoen , Andrew Morton , John Stultz , linux-arm-kernel@lists.arm.linux.org.uk, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20090603033603.GA31488@linux-sh.org> References: <20090602071718.GA17710@linux-sh.org> <1243927502.23657.5619.camel@twins> <20090602073515.GB17710@linux-sh.org> <1243928495.23657.5642.camel@twins> <20090602075409.GA19294@linux-sh.org> <1243943366.6592.434.camel@desktop> <20090603033603.GA31488@linux-sh.org> Content-Type: text/plain Date: Wed, 03 Jun 2009 07:58:08 -0700 Message-Id: <1244041088.18985.9.camel@desktop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2169 Lines: 48 On Wed, 2009-06-03 at 12:36 +0900, Paul Mundt wrote: > On Tue, Jun 02, 2009 at 04:49:26AM -0700, Daniel Walker wrote: > > On Tue, 2009-06-02 at 16:54 +0900, Paul Mundt wrote: > > > unsigned long long __attribute__((weak)) sched_clock(void) > > > { > > > - return (unsigned long long)(jiffies - INITIAL_JIFFIES) > > > - * (NSEC_PER_SEC / HZ); > > > + unsigned long long time; > > > + struct clocksource *clock; > > > + > > > + rcu_read_lock(); > > > + clock = rcu_dereference(sched_clocksource); > > > + time = cyc2ns(clock, clocksource_read(clock)); > > > + rcu_read_unlock(); > > > + > > > + return time; > > > } > > > > My concerns with the locking here still stand. Nothing you've said or > > done bolsters the clocksource in modules argument. I think what your > > planning for sh clocksources seems very inelegant. I would imagine a > > better solution is out there. I'd prefer if you just leave sched_clock > > alone. > > > This is the first I've heard you mention locking concerns, and as usual > there is not enough technical content (or any, really) to go on to even > reply to this. Whether you consider my solution for sh clocksources > elegant or not is irrelevant, as I wasn't soliciting feedback, and it's a > problem that has to be dealt with regardless of whether it's a pretty one > or not. I think maybe your not reading my emails .. I said there is unnessesary locking in sched_clock, and that it's fixing a problem that doesn't exist (i.e. clocksources in modules) .. You claim you want clocksources in modules because you have a useful case in sh, which I consider not very useful .. And your refusing to remove the locking, or that's how it seems. So I'd prefer you don't submit this code any longer. I don't think you know what your doing in this case. This is not hand waving, and it is technical. Daniel -- 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/