Idle-priority scheduling fix

[Brian Rogers]

Hello Ubuntu kernel team,

A bug with idle priority scheduling has been fixed in 2.6.29. Since I 
learned that Jaunty will release with 2.6.28, I wanted to make sure this 
fix gets in. The commits to cherry-pick are:

cce7ade803699463ecc62a065ca522004f7ccb3d
6bc912b71b6f33b041cfde93ca3f019cbaa852bc

The impact is that the whole system becomes sluggish while idle-priority 
tasks are running. Programs such as BOINC trigger this. The system will 
freeze randomly for a couple seconds at a time, especially if there are 
also normal-priority processes competing for time. It is also possible, 
with no special privileges, to create one idle priority process per CPU 
and put them all into busy loops at the same time, which will cause the 
whole system to freeze up to the point that it doesn't respond to mouse 
movement for several minutes.

Bug report here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/276476

This issue also affects 2.6.27, so it'd be nice to get an SRU for 
Intrepid as well. There's a backport to 2.6.27 at 
http://patchwork.kernel.org/patch/4914/

Brian