From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Rompf Subject: Re: [PATCH] core: linkwatch should use jiffies64 Date: Mon, 8 May 2006 20:28:56 +0200 Message-ID: <200605082028.57328.stefan@loplof.de> References: <200605071213.56877.stefan@loplof.de> <20060507.230727.67882043.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org Return-path: Received: from nattrymon.rzone.de ([81.169.145.178]:20709 "EHLO nattrymon.rzone.de") by vger.kernel.org with ESMTP id S1751274AbWEHS2R (ORCPT ); Mon, 8 May 2006 14:28:17 -0400 To: "David S. Miller" In-Reply-To: <20060507.230727.67882043.davem@davemloft.net> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Am Montag 08 Mai 2006 08:07 schrieb David S. Miller: > What is so special about what linkwatch is doing such > that it needs this kind of treatment and other similar > pieces or code do not? > > We have all sorts of interfaces such as time_after() et el. > in order to deal with wrapping issues. time_after() and friends can handle jiffies wrapping, however they require the difference between compared times to be less than 0x80000000 jiffies (about 24 days on HZ=1000) to work reliably on 32bit architectures. So if the network is stable for 24 days, events generated within days 25-49 will suffer a *huge* false delay. > And furthermore > using 64-bit jiffies here might not be appropriate because > they are not guarenteed to be accessed atomically, get_jiffies_64() handles this transparently. Stefan