On 7/21/2011 8:32 AM, Rob Herring wrote:
On 07/20/2011 06:32 PM, Mike Turquette wrote:
A quick poll of the ARM platforms that implement CPU Hotplug support
shows that every platform treats CPU 0 as a special case that cannot be
hotplugged. In fact every platform has identical code for
platform_cpu_die which returns -EPERM in the case of CPU 0.
The user-facing sysfs interfaces should reflect this by not populating
an 'online' entry for CPU 0 at all. This better reflects reality by
making it clear to users that CPU 0 cannot be hotplugged.
This patch prevents CPU 0 from being marked as hotpluggable on all ARM
platforms during CPU registration. This in turn prevents the creation
of an 'online' sysfs interface for that CPU.
Unless there is a kernel limitation why CPU0 can't be hot unplugged,
then this should remain a platform decision. This may be another case of
everybody just copying other platforms' code, not a platform limitation.
Just talking on behalf of OMAP, we can't offline CPU0 and limitation
would remain in future OMAPs too.
Regards
Santosh
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