Idle-priority scheduling fix

[Andy Whitcroft]

On Sun, Feb 22, 2009 at 12:48:04AM -0800, Brian Rogers wrote:
> 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/

I will have a look at these patches and see if they are now in Jaunty et
al.

-apw