I see this during suspend/resume, and sometimes it results in lockup, requiring a restart of lightdm.
I think it might be safe to say that this regression happened somewhere between Linux kernel 3.13 and 3.16. I was previously running Ubuntu 14.04 LTS (with the 3.13 kernel) and there were no issues. However, running Ubuntu 14.04 LTS with the upstream 3.16 kernel gave this warning. After upgrading to Ubuntu 14.10 LTS (with the Ubuntu 3.16 kernel), the problem persisted.
I see this during suspend/resume, and sometimes it results in lockup, requiring a restart of lightdm.
I think it might be safe to say that this regression happened somewhere between Linux kernel 3.13 and 3.16. I was previously running Ubuntu 14.04 LTS (with the 3.13 kernel) and there were no issues. However, running Ubuntu 14.04 LTS with the upstream 3.16 kernel gave this warning. After upgrading to Ubuntu 14.10 LTS (with the Ubuntu 3.16 kernel), the problem persisted.