Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763696AbXIKXK2 (ORCPT ); Tue, 11 Sep 2007 19:10:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755965AbXIKXKV (ORCPT ); Tue, 11 Sep 2007 19:10:21 -0400 Received: from py-out-1112.google.com ([64.233.166.180]:26796 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751274AbXIKXKU convert rfc822-to-8bit (ORCPT ); Tue, 11 Sep 2007 19:10:20 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Zf+qY+ZbKleQYvWdAslv/zwkADsPzCD0MDsLGv8lsw7p4YGNEVwpWw+IPxkogg4olLF7o2PsdgSkeEQ1y5IFtEPOKXGsCXdXxsutk4uYpQ6gyg+7Yjzquy4INumZ2UVGGHQOX55tv8Pvv5I3e7EPrAUybq3pH7ZfCAmUlmC9E5E= Message-ID: <8b67d60709111610s41e1964dsc2fe21a6eca4096@mail.gmail.com> Date: Wed, 12 Sep 2007 00:10:19 +0100 From: "Adrian McMenamin" To: "=?ISO-8859-1?Q?Bj=F6rn_Steinbrink?=" Subject: Re: time_after - what on earth??? Cc: "Rene Herman" , linux-kernel@vger.kernel.org, linuxsh-dev@lists.sourceforge.net, "Paul Mundt" In-Reply-To: <20070911230940.GA7070@atjola.homenet> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline References: <8b67d60709111505u61771a1do74c82a55430ec214@mail.gmail.com> <46E7128D.1080006@gmail.com> <8b67d60709111515m5b45c57emef5cc2f74795ed7a@mail.gmail.com> <46E7145D.10907@gmail.com> <20070911230940.GA7070@atjola.homenet> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1791 Lines: 43 On 12/09/2007, Bj?rn Steinbrink wrote: > On 2007.09.12 00:19:09 +0200, Rene Herman wrote: > > On 09/12/2007 12:15 AM, Adrian McMenamin wrote: > > > >> On 11/09/2007, Rene Herman wrote: > >>> On 09/12/2007 12:05 AM, Adrian McMenamin wrote: > >>> > >>>> OK, why does this line occasionally return true: > > What exactly is "occassionally"? Does it happen more than once per > boot? If not, and it happens after a certain time after booting, it > might be wrapping of the jiffie counter (see below). > > >>>> > >>>> if ((maple_dev->interval > 0) && (jiffies >maple_dev->when)) > >>>> > >>>> while this one never does (no other changes made): > >>>> > >>>> if ((maple_dev->interval > 0) && (time_after(jiffies, > >>>> maple_dev->when))) > >>> Is maple_dev->when an unsigned long? > >>> > >> Yes. Does that make a difference? > > > > If it had been a signed type, it could've wrapped to something you didn't > > expect, explaining the difference at least... > > > > With an unsigned long, the only diference should be that time_after() deals > > with jiffie wrapping which I assume is not an actual problem here. I'll > > retreat into the shades again... ;-( > > If "occasionally" is limited to once per boot, it might be jiffie > wrapping. IIRC jiffies are initialized so that they wrap after about 5 > minutes of uptime to reveal such bugs without forcing you to wait for > ages just to have the counter wrap for the first time. > No, I mean "works properly" - ie occasionally evaluates as true - 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/