linux-kernel - Re: /sys/devices/system/cpu/cpuX/online are missing

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Message-ID: <20070313094038.GA20518@flint.arm.linux.org.uk>
Date:	Tue, 13 Mar 2007 09:40:39 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Andreas Schwab <schwab@...e.de>,
	Giuliano Pochini <pochini@...ise.shiny.it>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: /sys/devices/system/cpu/cpuX/online are missing

On Tue, Mar 13, 2007 at 10:11:59AM +0100, Heiko Carstens wrote:
> On Tue, Mar 13, 2007 at 10:03:50AM +0100, Heiko Carstens wrote:
> > On Tue, Mar 13, 2007 at 01:39:25AM +0100, Andreas Schwab wrote:
> > > Giuliano Pochini <pochini@...ise.shiny.it> writes:
> > > 
> > > > I had a look at arch/powerpc/kernel/smp.c but I'm not familiar at all with 
> > > > those parts of the kernel.
> > > 
> > > See arch/powerpc/kernel/sysfs.c:topology_init.  I don't think there is
> > > anything to do here.  You probably don't have CONFIG_HOTPLUG_CPU enabled.
> > 
> > I was referring to arch/ppc not arch/powerpc. But it seems that arch/ppc
> > doesn't support cpu hotplug anyway. So I guess it's indeed just a missing
> > config option.
> > 
> > Grepping a bit further shows that arm suffered by the change that inverted
> > the logic if the 'online' attribute for cpus should appear. Since arm
> > supports cpu hotplug but the patch left arm out, it doesn't work there
> > anymore (cc'ing arm people: changeset 72486f1f8f0a2bc828b9d30cf4690cf2dd6807fc
> > is most probably disabling cpu hotplug support on arm like it did on s390).
> 
> Should have cc'ed Suresh Siddha who caused the breakage ;)

Welcome to why cleanups are bad news. ;(  Yes, ARM also needs to be fixed
and I'd ask that in future people doing cleanups in core code take a little
more time to review the code before submitting patches *AND* give heads-up
to *EVERYONE* who might be affected by the change.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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