Capsule review

Unix was designed to support client address spaces containing exactly one program counter. This assumption about a Unix process has had a remarkably pervasive influence on the interface to the Unix kernel. This report documents a successful project to provide an alternative interface, for multithreaded address spaces, to the Unix file and process facilities. Single-threaded processes using the Unix kernel interface and multi-threaded processes using the alternative can cohabit the same system and cooperate.

Part I of the report is a paper that discusses the general issues and solutions. Part II is a programmer's manual for the new interface. The inclusion of this second part will allow the interested reader to answer quite detailed questions about how the system may be used. The techniques discussed in Part I will apply to efforts to provide a more modern, multi-threaded interface to other operating systems with single-threaded client interfaces.

Michael Schroeder