linux-kernel - Re: [tps_init] BUG: unable to handle kernel paging request at 484970c9

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Date:	Sun, 25 Aug 2013 12:39:24 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, Samuel Ortiz <sameo@...ux.intel.com>,
	Ben Dooks <ben@...tec.co.uk>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [tps_init] BUG: unable to handle kernel paging request at
 484970c9

On Sat, Aug 24, 2013 at 09:09:39PM -0700, Greg KH wrote:
> On Sun, Aug 25, 2013 at 08:04:21AM +0800, Fengguang Wu wrote:
> > Greetings,
> > 
> > It seems the below patch discloses a bug in tps_init().
> > 
> > commit c817a67ecba7c3c2aaa104796d78f160af60920d
> > Author: Russell King <rmk+kernel@....linux.org.uk>
> > Date:   Thu Jun 27 15:06:14 2013 +0100
> > 
> >     kobject: delayed kobject release: help find buggy drivers
> >     
> >     Implement debugging for kobject release functions.  kobjects are
> >     reference counted, so the drop of the last reference to them is not
> >     predictable. However, the common case is for the last reference to be
> >     the kobject's removal from a subsystem, which results in the release
> >     function being immediately called.
> >     
> >     This can hide subtle bugs, which can occur when another thread holds a
> >     reference to the kobject at the same time that a kobject is removed.
> >     This results in the release method being delayed.
> >     
> >     In order to make these kinds of problems more visible, the following
> >     patch implements a delayed release; this has the effect that the
> >     release function will be out of order with respect to the removal of
> >     the kobject in the same manner that it would be if a reference was
> >     being held.
> >     
> >     This provides us with an easy way to allow driver writers to debug
> >     their drivers and fix otherwise hidden problems.
> >     
> >     Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
> >     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 

> > Parent commit not clean. Look out for wrong bisect!
> > 
> > BUG: kernel boot crashed
> > 
> > /kernel/i386-randconfig-j1-08220808/7c42721fe0c58a848849b43ff558cf2fb86aa35a/dmesg-kvm-nhm4-6710-20130824125721-3.11.0-rc2-00007-ge56341a-282

Sorry please ignore the above several lines.

> > [    0.304827] WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:530 sysfs_add_one+0x89/0x9b()
> > [    0.306316] sysfs: cannot create duplicate filename '/bus/i2c/drivers/tps65010'
> 
> Same as before, are you unloading and loading modules?  We have a fix
> for modules that cause problems when unloading with the config option
> above enabled.  But that shouldn't be this issue.

At least I didn't explicitly unloading modules. Judging from the
timestamp [    0.304827], the user space has not started yet.

Thanks,
Fengguang
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