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

[Stefan Bader]

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.

Testcase: Booting testkernel on the Acer Aspire One and for comparison on a 
Dell Inspiron 1521. The Acer succeeds in rebooting without panic and the Dell 
still does the same.

--

When all other means of communication fail, try words!


-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-UBUNTU-SAUCE-init-Stop-other-threads-before-calli.patch
Type: text/x-diff
Size: 2418 bytes
Desc: not available
URL: <https://lists.ubuntu.com/archives/kernel-team/attachments/20090713/80749f13/attachment.patch>