Re: [RFC PATCH]: ACPI: Automatically online hot-added memory

[Prarit Bhargava <prarit@redhat.com>]

Thomas Renninger wrote:
> On Thursday 11 March 2010 09:32:09 chen gong wrote:
>   
>> On 2010-3-11 16:07, ykzhao wrote:
>>     
> ... 
>   
>> BTW, how about using UDEV rules to do this operation. It looks more smooth. I know some
>> Novell guy is working on it.
>>     
> I also know this guy :)
>
> These would be the udev rules to automatically add memory/cpus:
> SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1", RUN+="/bin/logger onlining cpu: $env{DEVPATH}"
> SUBSYSTEM=="memory", ACTION=="add", TEST=="state", ATTR{state}=="offline", ATTR{state}="online", RUN+="/bin/logger onlining memory: $env{DEVPATH}"
>
> But this should be the same as you suggest (at least the memory rule)
> to do in the kernel:
> automatically online the memory, once hotadded.
>
> I would not add any udev rules before this does not work
> reliably and currently it is totally broken, mainly because:
>   - not being able to alloc memory on foreign nodes (at least with slab)
>   - C-state, throttling and cpufreq set up is done without valid
>     cpu_data(new_cpu) resulting in wrong C-state (and other) info
>
>   

Thomas, forgive my ignorance of udev rules ... but can one udev rule 
block another?  ... That's not the best way to explain it ... here's an 
example:

CPU hot add on Nehalem-EX.  Memory is brought online.  Memory udev 
events are generated.  CPU udev events are generated.

Can the memory udev events block the cpu udev events?  ie) can I be 
assured that memory will come online before the cpus?

P.

>    Thomas
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