From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264542AbUAFRF2 (ORCPT ); Tue, 6 Jan 2004 12:05:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264546AbUAFRF2 (ORCPT ); Tue, 6 Jan 2004 12:05:28 -0500 Received: from fw.osdl.org ([65.172.181.6]:30856 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S264542AbUAFRFT (ORCPT ); Tue, 6 Jan 2004 12:05:19 -0500 Date: Tue, 6 Jan 2004 09:05:21 -0800 From: Andrew Morton To: James Bottomley Cc: johnstul@us.ibm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fix get_jiffies_64 to work on voyager Message-Id: <20040106090521.4a7ad2a0.akpm@osdl.org> In-Reply-To: <1073406369.2047.33.camel@mulgrave> References: <1073405053.2047.28.camel@mulgrave> <20040106081947.3d51a1d5.akpm@osdl.org> <1073406369.2047.33.camel@mulgrave> X-Mailer: Sylpheed version 0.9.4 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org James Bottomley wrote: > > On Tue, 2004-01-06 at 10:19, Andrew Morton wrote: > > Hm, OK. I hit the same deadlock when running with the "don't require TSCs > > to be synchronised in sched_clock()" patch from -mm. The fix for that is > > below. I shall accelerate it. > > Actually, I think we need to know why this is happening, since the use > of these sequence locks is growing. That would be nice. Can you get a backtrace? > On voyager I just put it down to HZ > == 1000 being a bit much for my old pentium 66MHz processors, but if > you've seen it on a much faster processor, that would tend to indicate > there's some other problem at work here. No, it was much simpler in my case: log_buf_len_setup() was accidentally enabling interrupts early in boot and we were taking a timer interrupt while holding a write lock on xtime_lock. sched_clock() was requiring a read lock and boom.