I ran a bisect which traced it to this commit: "4f83989 sched: Fix race in task_group()"
This commit is included in 3.5.5 and 3.6-rc1 and later.
I ran a bisect which traced it to this commit: "4f83989 sched: Fix race in task_group()"
This commit is included in 3.5.5 and 3.6-rc1 and later.