Using ENQ/DEQ or Latch Manager Services with Enclaves

There are some considerations to be aware of when using enclaves for tasks or SRBs that serialize on resources using the ENQ macro or the latch manager callable services. A task cannot change its transaction status, that is, cannot join or leave an enclave, while holding a resource using ENQ or the latch manager; an SRB cannot issue SYSEVENT ENCASSOC while holding a resource using the latch manager. Otherwise, enqueue promotion processing may not work properly. The recommended sequence is:

• Task: Join an enclave using IWMEJOIN or IWM4STBG. SRB: Associate enclave with an address space using SYSEVENT ENCASSOC.
• Obtain resource with ENQ or latch manager.
• Release resource.
• Task: Leave an enclave using IWMELEAV or IWM4STEN. SRB: Disassociate enclave from the address space using SYSEVENT ENCASSOC.

In addition, to ensure correct enqueue promotion processing, a task executing in an enclave should not make the following types of ENQ requests:

• Directed enqueues, that is, issuing the ENQ macro with the TCB= parameter
• Matching task enqueues, that is, issuing the ENQ macro with the MASID= and MTCB= parameters