DCE Application Programming Guide

Application Programming With NonStop DCE

Threads

HP NonStop DCE Application Programming Guide—429551-003

3-8

Spawning a New Process

Using any version of the fork functions in a multithreaded environment can cause

problems. Section 8.13 of the OSF DCE Application Development Guide discusses the

various problems associated with using those functions.

Applications can use a fork function safely under these conditions:

•

A parent process can safely spawn a child process if the parent process invokes

the fork() or tdm_fork() function before calling any function in the DCE API.

This method is often used to create a demon process that can run in the

background.

•

A parent process that has already called a function in the DCE API can also use a

fork function to create a child process if the child process calls the exec(),

tdm_execve(), or tdm_execep() function immediately upon its creation. (For

more information about the use of exec functions, see Section 8.13 of the OSF

DCE Application Development Guide.)

Isolating Faults

Because all threads created by a process share the process address space, there is

no protection between threads. An application thread can corrupt data, causing other

threads or the entire process to fail.

NonStop DCE Jacket Routines

A jacket routine invokes a nonblocking (nowait) version of a Guardian procedure call

and suspends the thread until the thread’s operation is complete. NonStop DCE

provides jacket routines for SERVERCLASS_SEND_, SERVERCLASS_SEND_INFO_,

SERVERCLASS_DIALOG_BEGIN_, SERVERCLASS_DIALOG_SEND_,

SERVERCLASS_DIALOG_END_, and SERVERCLASS_DIALOG_ABORT_ calls and for

TMF transaction demarcation.

SERVERCLASS_SEND_ Jacket

The DCE_SERVERCLASS_SEND_() function in the threads library is used for sending a

message to and receiving a reply from a server process in a Pathway server class.

This jacket routine invokes a nowait version of the Guardian SERVERCLASS_SEND_

procedure. The thread that makes the call is suspended until the send operation has

finished. Another jacket, the DCE_SERVERCLASS_SEND_INFO_() function, is also

provided. It returns information about the last DCE_SERVERCLASS_SEND_() call that

was attempted or completed by the current thread. The

DCE_SERVERCLASS_SEND_INFO_() function ensures that the thread gets the

information for the last message sent by the thread rather than by the process. See

SERVERCLASS_SEND_INFO_ Jacket.