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STREAMS Programming Guide     Oracle Solaris 11.1 Information Library
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Part I Application Programming Interface

1.  Overview of STREAMS

2.  STREAMS Application-Level Components

3.  STREAMS Application-Level Mechanisms

4.  Application Access to the STREAMS Driver and Module Interfaces

5.  STREAMS Administration

6.  Pipes and Queues

Part II Kernel Interface

7.  STREAMS Framework - Kernel Level

8.  STREAMS Kernel-Level Mechanisms

9.  STREAMS Drivers

10.  STREAMS Modules

11.  Configuring STREAMS Drivers and Modules

12.  Multithreaded STREAMS

Multithreaded (MT) STREAMS Overview

MT STREAMS Framework

STREAMS Framework Integrity

Message Ordering

MT STREAMS Perimeters

Inner Perimeters

Outer Perimeters

PERMOD Perimeter

Hot Perimeters

Defining Perimeter Types

Choosing a Perimeter Type

MT SAFE Modules and Drivers

MT SAFE Module

MT SAFE Driver

Routines Used Inside a Perimeter





Asynchronous Callback Functions

close() Race Conditions

Unloading a Module that Uses esballoc

Use of the q_next Field

MT SAFE Modules Using Explicit Locks

Constraints When Using Locks

Preserving Message Ordering

Preparing to Port

Porting to the SunOS 5 System

Sample Multithreaded Device Driver Using a Per Module Inner Perimeter

Sample Multithreaded Module With Outer Perimeter

13.  STREAMS Multiplex Drivers

Part III Advanced Topics

14.  Debugging STREAMS-based Applications

Part IV Appendixes

A.  Message Types

B.  Kernel Utility Interface Summary

C.  STREAMS-Based Terminal Subsystem




MT SAFE Modules Using Explicit Locks

Although the result is not reliable, you can use explicit locks either instead of perimeters or to augment the concurrency restrictions provided by the perimeters.


Caution - Explicit locks cannot be used to preserve message ordering in a module because of the risk of re-entering the module. Use MT STREAMS perimeters to preserve message ordering.

All four types of kernel synchronization primitives are available to the module writer: mutexes, readers/writer locks, semaphores, and condition variables. Because cv_wait implies a context switch, it can only be called from the module's open and close procedures, which are executed with valid process context. You must use the synchronization primitives to protect accesses and ensure the integrity of private module data structures.

Constraints When Using Locks

When adding locks in a module, observe these constraints:

The first restriction deters using module private locks to preserve message ordering. The preferred mechanism is to use MT STREAMS perimeters to preserve message ordering.

Preserving Message Ordering

Module private locks cannot be used to preserve message ordering because they cannot be held across calls to putnext(9F) and the other messages that pass routines to other modules. The alternatives for preserving message ordering are:

Use perimeters to avoid the performance penalty for using service procedures.