Another issue was that ftrace was not a suspect at the time. I corrected any bugs that were passed on to me.
We were designing a new (more robust) version of ftrace in the linux-tip tree. This new version does not have the problems that the old version (in 2.6.27) had. But since the new version was a new design, we held off pushing it to Linus.
Unfortunately, all our testing of the old design never showed any of these issues. It took going out to a larger audience to have them appear.