2.2.12 btrfs, ext4 and xfs: Kernel panic when freeze and unfreeze operations are performed in multiple threads

Freeze and unfreeze operations performed across multiple threads on any supported file system can cause the system to hang and the kernel to panic. This 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)