From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932272AbYBNWEW (ORCPT ); Thu, 14 Feb 2008 17:04:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755105AbYBNWEO (ORCPT ); Thu, 14 Feb 2008 17:04:14 -0500 Received: from sj-iport-3.cisco.com ([171.71.176.72]:20659 "EHLO sj-iport-3.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752341AbYBNWEM (ORCPT ); Thu, 14 Feb 2008 17:04:12 -0500 To: "Tony Luck" Cc: "David Miller" , mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: Strange hang on ia64 with CONFIG_PRINTK_TIME=y X-Message-Flag: Warning: May contain useful information References: <20080213125725.GC6344@elte.hu> <20080213.050340.64342037.davem@davemloft.net> <12c511ca0802131659u6e4407d9w96148fe72d6e11d7@mail.gmail.com> <20080213.170452.68851396.davem@davemloft.net> <12c511ca0802131933g6aaaec9cidbfbfcac6f394c63@mail.gmail.com> <12c511ca0802141327j6e31e8c2tee1d679053b604fc@mail.gmail.com> From: Roland Dreier Date: Thu, 14 Feb 2008 14:04:05 -0800 In-Reply-To: <12c511ca0802141327j6e31e8c2tee1d679053b604fc@mail.gmail.com> (Tony Luck's message of "Thu, 14 Feb 2008 13:27:58 -0800") Message-ID: User-Agent: Gnus/5.1008 (Gnus v5.10.8) XEmacs/21.4.21 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 14 Feb 2008 22:04:05.0976 (UTC) FILETIME=[8421A580:01C86F55] Authentication-Results: sj-dkim-8; header.From=rdreier@cisco.com; dkim=pass ( sig from cisco.com/sjdkim8002 verified; ); Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > The strange thing is that Ingo's patch to make cpu_clock() a NOP until > > after sched_init() didn't fix things for me... > Very strange. I threw in an output line counter into the printk code() ... if I > disable the timestamps for the first 30 lines, then everything is good (so the > basic timestamping code does still work on ia64). But I would have thought > that Ingo's delay until sched_init() ought to be long enough too. Clearly I > need to figure out exactly what needs to be initialized to prevent the > hang/crash. I guess sched_init() is too early... it does seem really strange to me, but I just double checked with Ingo's patch and it does indeed hang. The slow way to make progress is just to go through start_kernel() line-by-line and enable cpu_clock() at each stage, and see where it stops hanging. I'll give that a shot as a background process (my ia64 box takes quite a while to boot, so each test takes a long time but requires very little of my attention).