2.2.12 Btrfs, ext4, and XFS: kernel panic when freeze and unfreeze operations are performed on multiple threads

Freeze and unfreeze operations that are performed across multiple threads on any supported file system can cause the system to hang and the kernel to panic. This problem is the result of a race condition that occurs when the unfreeze operation is triggered before it is actually frozen. The resulting unlock operation attempts a write operation on a non-existent lock resulting in the kernel panic. (Bug ID 25321899)