If an asynchronous signal is being delivered to a thread running
with POSIX(ON), the thread is interrupted for the signal only when
the execution is:
- In a user C routine, or in a user COBOL routine compiled with
the THREAD compiler option
- Just before a return to a C routine or to a return to a user
COBOL routine compiled with the THREAD compiler option
- Just before an invocation of a Language Environment library from a user routine
C routines or COBOL routines compiled with the THREAD compiler
option may need to protect against asynchronous signals based on the
application logic including the possible use of the POSIX signal-blocking
function that is available.