int splstr()
The splstr utility increases the system processor level in order to block interrupts at a level appropriate for STREAMS modules and drivers when they are executing critical portions of their code. The splstr utility returns the processor level at the time of its invocation. Module developers are expected to use the standard splx(s) utility, where s is the integer value returned by the splstr operation, to restore the processor level to its previous value after the critical portions of code are passed.
This utility is part of STREAMS Kernel Extensions.
The splx utility.
List of Streams Programming References and STREAMS Overview in AIX Version 4.3 Communications Programming Concepts.