There are situations where the system does not provide serialization between recovery routines for different TCBs in an address space. When possible you should write your recovery routines so that serialization is not required.
When a recovery routine requires serialization with other TCBs in the address space then the recovery routine must provide its own serialization. Serialization must be carefully designed to avoid causing deadlock situations.
One serialization technique to ensure the order of termination processing is to use the DETACH macro. Issuing DETACH ensures that the detached task and its recovery routines complete before processing for the issuing task proceeds. DETACH can only be used for tasks that were directly attached by the recovery routine's TCB.
Another important aspect of recovery is releasing resources. Releasing serialization resources (locks, ENQs, latches) in ESTAE-type recovery routines, rather than leaving them to be released by a resource manager, helps avoid deadlocks in recovery processing.