From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261292AbVECBbx (ORCPT ); Mon, 2 May 2005 21:31:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261283AbVECBbn (ORCPT ); Mon, 2 May 2005 21:31:43 -0400 Received: from gate.crashing.org ([63.228.1.57]:54953 "EHLO gate.crashing.org") by vger.kernel.org with ESMTP id S261287AbVECBbW (ORCPT ); Mon, 2 May 2005 21:31:22 -0400 Subject: Re: [PATCH] fix __mod_timer vs __run_timers deadlock. From: Benjamin Herrenschmidt To: Lee Revell Cc: Juergen Kreileder , Andrew Morton , Oleg Nesterov , linux-kernel@vger.kernel.org, maneesh@in.ibm.com In-Reply-To: <1115083453.27658.6.camel@mindpipe> References: <42748B75.D6CBF829@tv-sign.ru> <20050501023149.6908c573.akpm@osdl.org> <87vf61kztb.fsf@blackdown.de> <1115079230.6155.35.camel@gaston> <1115083453.27658.6.camel@mindpipe> Content-Type: text/plain Date: Tue, 03 May 2005 11:28:51 +1000 Message-Id: <1115083731.6156.39.camel@gaston> Mime-Version: 1.0 X-Mailer: Evolution 2.2.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2005-05-02 at 21:24 -0400, Lee Revell wrote: > On Tue, 2005-05-03 at 10:13 +1000, Benjamin Herrenschmidt wrote: > > Well, there may be other issues brought by this new timer code though. > > I'm running G5s regulary without a lockup or anything for weeks, so it > > would be interesting if you could try to find out what's involved in > > that other lockup you had. > > It seems like it would not be to hard to create a timer test suite that > just hammers the timer subsystem, creating and deleting and modifying > zillions of timers, changing the system time, etc. Combined with > running with HZ=10000 or something it seems like you could shake out > bugs a lot faster than just running & waiting for a race to show up. Well, yes and know... the timer subsytem is very senstivie to things like memory barriers issues, and thus changes in the "barrier" semantics of a timer call may have an impact on the caller code regardless of the validity of the timer code itself, that sort of thing ... > I've seen timer related issues (the set_rtc_mmss issue that George > Anzinger fixed) while testing the RT patchset that I could only ever > reproduce once.