linux-kernel - Re: x86: 4kstacks default

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Date:	Fri, 25 Apr 2008 17:39:53 +0000 (UTC)
From:	Parag Warudkar <parag.warudkar@...il.com>
To:	linux-kernel@...r.kernel.org
Subject:  Re: x86: 4kstacks default

Andrew Morton <akpm <at> linux-foundation.org> writes:

> 
> > On Sat, 19 Apr 2008 16:23:29 +0200 Ingo Molnar <mingo <at> elte.hu> wrote:
> > 
> > * Andrew Morton <akpm <at> linux-foundation.org> wrote:
> > 
> > > >  config 4KSTACKS
> > > >  	bool "Use 4Kb for kernel stacks instead of 8Kb"
> > > > -	depends on DEBUG_KERNEL
> > > >  	depends on X86_32
> > > > +	default y
> > > 
> > > This patch will cause kernels to crash.
> > 
> > what mainline kernels crash and how will they crash?
> 
> There has been a dribble of reports - I don't have the links handy, nor did
> I search for them.
> 
> > Fedora and other 
> > distros have had 4K stacks enabled for years:
> > 
> >   $ grep 4K /boot/config-2.6.24-9.fc9
> >   CONFIG_4KSTACKS=y

Here is a report - Fedora 8 default kernel, Mac Mini file server, Not Tainted. 
Attempt to copy 100Gb+ of data from a hfsplus file system on a USB drive to a 
firewire drive with XFS filesystem - I got a nasty panic with a huge stack 
backtrace. I gave up and switched to Ubuntu. With a stock kernel.org kernel I 
was able to successfully copy the data over. I still have the machine and the 
restored drives and can try to reproduce it with Fedora 9 w/4K stacks if 
anyone thinks it is worthwhile (i.e. fixable).

Parag

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