Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752643AbaJFNBx (ORCPT ); Mon, 6 Oct 2014 09:01:53 -0400 Received: from www.linutronix.de ([62.245.132.108]:54225 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752462AbaJFNBw (ORCPT ); Mon, 6 Oct 2014 09:01:52 -0400 Date: Mon, 6 Oct 2014 15:01:48 +0200 (CEST) From: Thomas Gleixner To: Christoph Lameter cc: Richard Cochran , linux-kernel@vger.kernel.org Subject: Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days In-Reply-To: Message-ID: References: <20141003120345.GA6652@localhost.localdomain> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 6 Oct 2014, Christoph Lameter wrote: > For example the timer interrupt occurs 1000 times per second, so > it is predictable that the timer interrupt will overflow in Now the bad news is, that the timer interrupt if it is serviced via the local timer interrupt is still using a 32bit counter because the local timer interrupt does not go through the core interrupt code. So if you want to fix that as well, you really need to think about the 32 bit case because there is no serialization for the interrupts which are delivered directly from their own vector. And no, we should not diverge 32 and 64 bit artificially here simply because the same 50 days wrap applies to both. I really start to wonder whether all this is worth the trouble. It has been this way forever and 1k timer interrupts per second is not really a new thing either. So we did not change anything which suddenly makes tools confused. Thanks, tglx -- 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/