From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751144AbWDXXCA (ORCPT ); Mon, 24 Apr 2006 19:02:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751468AbWDXXCA (ORCPT ); Mon, 24 Apr 2006 19:02:00 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:42189 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751144AbWDXXB7 (ORCPT ); Mon, 24 Apr 2006 19:01:59 -0400 Subject: Re: Linux 2.6.17-rc2 - notifier chain problem? From: Chandra Seetharaman Reply-To: sekharan@us.ibm.com To: Andrew Morton Cc: herbert@13thfloor.at, torvalds@osdl.org, linux-kernel@vger.kernel.org, linux-xfs@oss.sgi.com, xfs-masters@oss.sgi.com, Alan Stern In-Reply-To: <20060424150314.2de6373d.akpm@osdl.org> References: <20060421110140.GC14841@MAIL.13thfloor.at> <1145655097.15389.12.camel@linuxchandra> <20060422005851.GA22917@MAIL.13thfloor.at> <1145913967.1400.59.camel@linuxchandra> <20060424150314.2de6373d.akpm@osdl.org> Content-Type: text/plain Organization: IBM Date: Mon, 24 Apr 2006 16:01:57 -0700 Message-Id: <1145919717.1400.67.camel@linuxchandra> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2006-04-24 at 15:03 -0700, Andrew Morton wrote: > Chandra Seetharaman wrote: > > > > Thanks for the steps. With that i was able to reproduce the problem and > > i found the bug. > > > > While i go ahead and generate the patch, i wanted to hear if my > > conclusion is correct. > > > > The problem is due to the fact that most notifier registrations > > incorrectly use __devinitdata to define the callback structure, as in: > > > > static struct notifier_block __devinitdata hrtimers_nb = { > > .notifier_call = hrtimer_cpu_notify, > > }; > > > > devinitdata'd data is not _expected to be available_ after the > > initialization(unless CONFIG_HOTPLUG is defined). > > > > I do not know how it was working until now :), anybody has a theory that > > can explain it (or my conclusion is wrong) ? > > That sounds right. There are several __devinitdata notifier_blocks in the > tree - please be sure to check them all. Yes, I am covering all notifier blocks. Another issue... many of the notifier callback functions are marked as init calls (__cpuinit, __devinit etc.,) as in: static int __cpuinit pageset_cpuup_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) I am generating a separate patch to take care of those too. > > btw, it'd be pretty trivial to add runtime checking for this sort of thing: > > int addr_in_init_section(void *addr) > { > return addr >= __init_begin && addr < __init_end; > } I will add this to kernel/sys.c, and put a BUG_ON to check for both the notifier block and the callback function. BTW, which header file you want me to export this through ? > > (x86-specific) > (need to add __init_end to vmlinux.lds.S) I see __init_end in arch/i386/kernel/vmlinux.lds.S. > > then we could use that to check various things in various places... -- ---------------------------------------------------------------------- Chandra Seetharaman | Be careful what you choose.... - sekharan@us.ibm.com | .......you may get it. ----------------------------------------------------------------------