Re: 2.6.25-rc regression: kernel panic on boot

[Ingo Molnar <mingo@elte.hu>]

* Greg KH <gregkh@suse.de> wrote:

> On Mon, Mar 03, 2008 at 07:25:49AM +0800, Zhang, Rui wrote:
> > Hi, all,
> > 
> > kernel panic on boot when I try to run 2.6.25-rc1 and later, but 2.6.24-rc8 boots okay.
> > The result of git-bisect shows that
> > edfaa7c36574f1bf09c65ad602412db9da5f96bf is first bad commit.
> > 
> > The git-bisect-result and the dmesg log when the kernel panic are 
> > attached. Any help on this please? :)
> 
> Are you using LVM?  If so, please either upgrade your userspace/initrd 
> stuff, or enable CONFIG_SYSFS_DEPCRECATED

we _really_ must handle this differently and this _is_ a regression that 
multiple people have spent hours on bisecting already ...

So "enable CONFIG_SYSFS_DEPCRECATED" is _NOT_ the right answer, and this 
has been pointed out to you in the past.

the problem is that SYSFS_DEPRECATED changed its meaning mid-course. Now 
it means a different set of udev breakages. The correct way is to 
_RENAME_ that darn option to SYSFS_DEPRECATED_V2 (via the patch below), 
and to discontinue the user-configurability of the old SYSFS_DEPRECATED 
option. Viola, things work just fine - and the fact of SYSFS_DEPRECATED 
changing its meaning is documented as well.

this way any tester who comes over the 'make oldconfig' route is not hit 
in the head with a nasty regression ...

tested patch below. (and this is one of those rare cases where 'select' 
is the right thing to do in a Kconfig entry)

	Ingo

---------------------->
Subject: sysfs: CONFIG_SYSFS_DEPRECATED fix
From: Ingo Molnar <mingo@elte.hu>
Date: Tue Mar 04 14:35:21 CET 2008

CONFIG_SYSFS_DEPRECATED=y changed its meaning recently and causes
regressions in working setups that had SYSFS_DEPRECATED disabled.

so rename it to SYSFS_DEPRECATED_V2 so that testers pick up the new
default via 'make oldconfig', even if their old .config's disabled
CONFIG_SYSFS_DEPRECATED ...

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 init/Kconfig |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux/init/Kconfig
===================================================================
--- linux.orig/init/Kconfig
+++ linux/init/Kconfig
@@ -367,9 +367,13 @@ config RESOURCE_COUNTERS
 	depends on CGROUPS
 
 config SYSFS_DEPRECATED
+	bool
+
+config SYSFS_DEPRECATED_V2
 	bool "Create deprecated sysfs files"
 	depends on SYSFS
 	default y
+	select SYSFS_DEPRECATED
 	help
 	  This option creates deprecated symlinks such as the
 	  "device"-link, the <subsystem>:<name>-link, and the