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

[Stefan Bader]

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.
> 
Applied, thanks

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