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:

quoted

On Tue, Mar 13, 2007 at 01:39:25AM +0100, Andreas Schwab wrote:

quoted

Giuliano Pochini [off-list ref] writes:

quoted

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: