Comment 54 for bug 290498

This bug appears to be solved in Karmic. As far as I can tell the current Karmic RT kernel (2.6.31-9-rt) does not have the SMP issue that Intrepid's and Jaunty's had.

If I had to guess, I would say this is because the kernel version matches the upstream RT patch version this time around, which hadn't happened since Hardy. In my opinion, the RT patch is highly non-trivial to port across kernel versions, and the Ubuntu linux-rt maintainers should stick to shipping the latest kernel version for which an RT patch was published, even if it doesn't match that of the generic kernel, because chances are that users will lose more from the RT kernel being broken than they would gain from having a newer kernel. Or to ship both.