To resolve the previous two issues, DCE Threads provides jacket routines for a number of UNIX system calls. Threads call the jacket routine instead of the UNIX system service; this allows DCE Threads to take action on behalf of the thread before or after calling the system service. For example, the jacket routines ensure that only one thread calls any particular service at a time to avoid problems with system calls that are not thread-reentrant.
Jacket routines are provided for UNIX input and output system calls (documented in any UNIX programmer's manual) and the fork( ) and sigaction( ) system calls. Jackets are not provided for any other UNIX system calls or for any of the C runtime library services. See /usr/include/dce/cma_ux.h for the full list of jacket routines.
More:
Input and Output Jacket Routines
Using the Jacketed System Calls