Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 24 Mar 2003 06:55:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 24 Mar 2003 06:55:03 -0500 Received: from lucifer.fast.no ([217.144.236.33]:55700 "HELO lucifer.fast.no") by vger.kernel.org with SMTP id ; Mon, 24 Mar 2003 06:55:02 -0500 Date: Mon, 24 Mar 2003 13:06:04 +0100 From: Finn Arne Gangstad To: Tim Schmielau Cc: Andrew Morton , Vitezslav Samel , Matthew Wilcox , Eric Piel , davidm@hpl.hp.com, linux-ia64@linuxia64.org, lkml Subject: Re: [PATCH] fix nanosleep() granularity bumps Message-ID: <20030324120604.GA3004@fast.no> References:

Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.3i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2356 Lines: 54 On Tue, Mar 18, 2003 at 10:05:56AM +0100, Tim Schmielau wrote: > On Mon, 17 Mar 2003, Tim Schmielau wrote: > > > I've re-checked that the problem does not occur with the original "initial > > jiffies" patch for 2.4. > > Stupid me - 2.4 with the patch has the same problem, it just takes 10x as > long to show up, a range that was not covered by the testcase. > > > The actual problem is that I didn't fully understand the, well, > 'elaborated' way of counting jiffies in the timer cascade: > > When starting out with timer_jiffies=0, the timer cascade is > (unneccessarily) triggered on the first timer interrupt, incrementing all > the higher indices. > When starting with any other initial jiffies value, we miss that and end > up with all higher indices being off by one. Suggest the attached patch as a fix instead - easier to understand I think and works for every possible start value. This is what I made for Andrea Arcangeli many years ago... diff -ur linux-2.5.65/kernel/timer.c linux-2.5.65-new/kernel/timer.c --- linux-2.5.65/kernel/timer.c 2003-03-17 22:44:41.000000000 +0100 +++ linux-2.5.65-new/kernel/timer.c 2003-03-24 12:57:31.000000000 +0100 @@ -1182,11 +1182,14 @@ INIT_LIST_HEAD(base->tv1.vec + j); base->timer_jiffies = INITIAL_JIFFIES; - base->tv1.index = INITIAL_JIFFIES & TVR_MASK; - base->tv2.index = (INITIAL_JIFFIES >> TVR_BITS) & TVN_MASK; - base->tv3.index = (INITIAL_JIFFIES >> (TVR_BITS+TVN_BITS)) & TVN_MASK; - base->tv4.index = (INITIAL_JIFFIES >> (TVR_BITS+2*TVN_BITS)) & TVN_MASK; - base->tv5.index = (INITIAL_JIFFIES >> (TVR_BITS+3*TVN_BITS)) & TVN_MASK; + base->tv1.index = (1 + (INITIAL_JIFFIES - 1)) & TVR_MASK; + base->tv2.index = (1 + ((INITIAL_JIFFIES - 1) >> TVR_BITS)) & TVN_MASK; + base->tv3.index = (1 + ((INITIAL_JIFFIES - 1) + >> (TVR_BITS + TVN_BITS))) & TVN_MASK; + base->tv4.index = (1 + ((INITIAL_JIFFIES - 1) + >> (TVR_BITS + 2 * TVN_BITS))) & TVN_MASK; + base->tv5.index = (1 + ((INITIAL_JIFFIES - 1) + >> (TVR_BITS + 3 * TVN_BITS))) & TVN_MASK; } static int __devinit timer_cpu_notify(struct notifier_block *self, - Finn Arne - 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/