[Hardy] SRU: Fix boot panic on Acer Aspire One (v2)

[Stefan Bader]

Tim Gardner wrote:
> Stefan Bader wrote:
>> SRU Justification:
>>
>> Impact: Certain kernel versions cause a kernel panic on the Acer Aspire
>> One when the kernel changes its data to read-only pages. The underlying
>> problem is very timing sensitive (adding printks for debugging makes the
>> problem much less likely to occur).
>>
>> Fix: As far as we understand, there might be another thread being
>> running (with a very speculative maybe related to freeing init memory)
>> which gets badly confused by the global_flush_tlb() (could also be
>> affected by the fact that changing the page attributes splits a large
>> kernel page). To prevent that we force all other CPUs to run the stop
>> work function, which basically acts like a  big sync. The performance
>> impact is minimal as this is done only once on boot. The change is
>> quirked to only happen on a Acer Aspire One.
>>
>> Testcase: Booting testkernel on the Acer Aspire One and for comparison
>> on a Dell Inspiron 1521. Quirk gets activated and boot succeeds on the
>> Acer while the Dell goes through the same code as before.
>>
> 
> ACK - thanks for accommodating my paranoia. A quick perusal of the bug
> report indicates that no one has tried a recent kernel. Is this patch
> needed in Karmic?
> 
> rtg

A definite no. I am running anything beyond Hardy without any problems. 
Actually after hardy the whole change page attributes stuff has been near 
completely reworked. So all OK beyond Hardy.


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