Re: nonboot cpu on SMP suspend

[Li Yang]

On Sat, Mar 21, 2009 at 2:58 AM, Pavel Machek <pavel@xxxxxx> wrote:
> On Wed 2009-03-18 14:25:32, Li Yang wrote:
>> Hi all,
>>
>> I'm curious why we need to un-plug all the nonboot cpus before suspend
>> and start them all over again after the suspend(ACPI sleep)? I mean
>> if we can bring the booting cpu back to the exact state as before
>> suspend, why can't we just do the same for non-booting cpus? And that
>> will be much faster. ÂAny thought? Thanks.
>
> Why do you think it will be faster?

_cpu_down() and _cpu_up() are surely complex functions, involving
work_queues and synchronization between boot cpu and non-boot cpu.  On
the contrary, to bring the cpu back to previous state is much simpler.
 For standby state, you barely need to do anything.  For mem state,
you only need to restore the registers and states of the CPU.

- Leo
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