Title and Copyright Information
 
About This Guide
Audience
Organization
Related Documents
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Conventions
 
1    Introduction to Realtime Programming
1.1    Realtime Overview
1.2    Tru64 UNIX Realtime System Capabilities
1.2.1    The Value of a Preemptive Kernel
1.2.1.1    Nonpreemptive Kernel
1.2.1.2    Preemptive Kernel
1.2.1.3    Comparing Latency
1.2.2    Fixed-Priority Scheduling Policies
1.2.3    Realtime Clocks and Timers
1.2.4    Memory Locking
1.2.5    Asynchronous I/O
1.2.6    Synchronized I/O
1.2.7    Realtime Interprocess Communication
1.3    Process Synchronization
1.3.1    Waiting for a Specified Period of Time or an Absolute Time
1.3.2    Waiting for Semaphores
1.3.3    Waiting for Communication
1.3.4    Waiting for Another Process
1.3.5    Realtime Needs and System Solutions
1.4    POSIX Standards
1.5    Enabling Tru64 UNIX Realtime Features
1.6    Building Realtime Applications
1.6.1    Defining the POSIX Environment
1.6.2    Compiling Realtime Applications
 
2    The Tru64 UNIX Scheduler
2.1    Scheduler Fundamentals
2.1.1    Schedulable Entities
2.1.2    Thread States
2.1.3    Scheduler Database
2.1.4    Quantum
2.1.5    Scheduler Transitions
2.2    Scheduling Policies
2.2.1    The Nature of the Work
2.2.2    Timesharing Scheduling
2.2.3    Fixed-Priority Scheduling
2.2.3.1    First-In First-Out Scheduling
2.2.3.2    Round-Robin Scheduling
2.3    Process Priorities
2.3.1    Priorities for the nice Interface
2.3.2    Priorities for the Realtime Interface
2.3.3    Displaying Realtime Priorities
2.3.4    Configuring Realtime Priorities
2.4    Scheduling Functions
2.4.1    Determining Limits
2.4.2    Retrieving the Priority and Scheduling Policy
2.4.3    Setting the Priority and Scheduling Policy
2.4.4    Yielding to Another Process
2.5    Priority and Policy Example
 
3    Shared Memory
3.1    Memory Objects
3.1.1    Opening a Shared-Memory Object
3.1.2    Opening Memory-Mapped Files
3.1.3    Mapping Memory-Mapped Files
3.1.4    Using File Functions
3.1.5    Controlling Memory-Mapped Files
3.1.6    Removing Shared Memory
3.2    Locking Shared Memory
3.3    Using Shared Memory with Semaphores
 
4    Memory Locking
4.1    Memory Management
4.2    Memory-Locking and Unlocking Functions
4.2.1    Locking and Unlocking a Specified Region
4.2.2    Locking and Unlocking an Entire Process Space
 
5    Signals
5.1    POSIX Signal Functions
5.2    Signal Handling Basics
5.2.1    Specifying a Signal Action
5.2.2    Setting Signal Masks and Blocking Signals
5.2.3    Suspending a Process and Waiting for a Signal
5.2.4    Setting Up an Alternate Signal Stack
5.3    Realtime Signal Handling
5.3.1    Additional Realtime Signals
5.3.2    Queuing Signals to a Process
5.3.2.1    The siginfo_t Structure
5.3.2.2    The ucontext_t and sigcontext Structures
5.3.2.3    Sending a Realtime Signal With the sigqueue Function
5.3.3    Asynchronous Delivery of Other Realtime Signals
5.3.4    Responding to Realtime Signals Using the sigwaitinfo and sigtimedwait Functions
 
6    Clocks and Timers
6.1    Clock Functions
6.1.1    Retrieving System Time
6.1.2    Setting the Clock
6.1.3    Converting Time Values
6.1.4    System Clock Resolution
6.1.5    High-Resolution Clock
6.2    Types of Timers
6.3    Timers and Signals
6.4    Data Structures Associated with Timing Facilities
6.4.1    Using the timespec Data Structure
6.4.2    Using the itimerspec Data Structure
6.4.3    Using the sigevent Data Structure
6.5    Timer Functions
6.5.1    Creating Timers
6.5.2    Setting Timer Values
6.5.3    Retrieving Timer Values
6.5.4    Getting the Overrun Count
6.5.5    Disabling Timers
6.6    High-Resolution Sleep
6.7    Clocks and Timers Example
 
7    Asynchronous Input and Output
7.1    Data Structures Associated with Asynchronous I/O
7.1.1    Identifying the Location
7.1.2    Specifying a Signal
7.2    Asynchronous I/O Functions
7.2.1    Reading and Writing
7.2.2    Using List-Directed Input/Output
7.2.3    Determining Status
7.2.4    Canceling I/O
7.2.5    Blocking to Completion
7.2.6    Asynchronous File Synchronization
7.3    Asynchronous I/O to Raw Devices
7.4    Asynchronous I/O Examples
7.4.1    Using the aio Functions
7.4.2    Using the lio_listio Function
 
8    File Synchronization
8.1    How to Assure Data or File Integrity
8.1.1    Using Function Calls
8.1.2    Using File Descriptors
 
9    Semaphores
9.1    Overview of Semaphores
9.2    The Semaphore Interface
9.2.1    Creating and Opening a Semaphore
9.2.2    Locking and Unlocking Semaphores
9.2.3    Priority Inversion with Semaphores
9.2.4    Closing a Semaphore
9.3    Semaphore Example
 
10    Messages
10.1    Message Queues
10.2    The Message Interface
10.2.1    Opening a Message Queue
10.2.2    Sending and Receiving Messages
10.2.3    Asynchronous Notification of Messages
10.2.4    Prioritizing Messages
10.2.5    Using Message Queue Attributes
10.2.6    Closing and Removing a Message Queue
10.3    Message Queue Examples
 
11    Realtime Performance and System Tuning
11.1    Realtime Responsiveness
11.1.1    Interrupt Service Routine Latency
11.1.2    Process Dispatch Latency
11.2    Improving Realtime Responsiveness
 
A    Tru64 UNIX Realtime Functional Summary
 
Examples
2-1    Initializing Priority and Scheduling Policy Fields
2-2    Using Priority and Scheduling Functions
3-1    Including a Shared-Memory Object
3-2    Locking a Memory Object
4-1    Aligning and Locking a Memory Segment
4-2    Using the mlockall Function
5-1    Sending a Signal to Another Process
5-2    Sending a Realtime Signal to Another Process
5-3    Using the sigwaitinfo Function
5-4    Using the sigwaitinfo Function
6-1    Returning Time
6-2    Using Timers
7-1    Using Asynchronous I/O
7-2    Using lio_listio in Asynchronous I/O
9-1    Locking a Semaphore
9-2    Using Semaphores and Shared Memory
10-1    Opening a Message Queue
10-2    Using Message Queues to Send Data
10-3    Using Message Queues to Receive Data
 
Figures
1-1    Nonpreemptive Kernel
1-2    Preemptive Kernel
2-1    Order of Execution
2-2    Process Events
2-3    Preemption - Finishing a Quantum
2-4    Priority Ranges for the nice and Realtime Interfaces
4-1    Memory Allocation with mlock
4-2    Memory Allocation with mlockall
5-1    Signal Mask that Blocks Two Signals
 
Tables
1-1    Realtime Needs and System Solutions
2-1    Priority Ranges for the nice Interface
2-2    Priority Ranges for the Tru64 UNIX Realtime Interface
3-1    Memory-Mapping Functions
3-2    Status Flags and Access Modes for the shm_open Function
3-3    File Functions Used with Memory-Mapped Files
5-1    POSIX 1003.1 Signal Functions
5-2    POSIX 1003.1b Signal Functions
5-3    POSIX Signals
6-1    Values Used in Setting Timers
10-1    Status Flags and Access Modes for the mq_open Function
A-1    Process Control Functions
A-2    P1003.1b Priority Scheduling Functions
A-3    P1003.1b Clock Functions
A-4    Date and Time Conversion Functions
A-5    P1003.1b Timer Functions
A-6    BSD Clock and Timer Functions
A-7    P1003.1b Memory Locking Functions
A-8    System V Memory Locking Function
A-9    P1003.1b Asynchronous I/O Functions
A-10    POSIX Synchronized I/O Functions
A-11    BSD Synchronized I/O Function
A-12    P1003.1b Message Functions
A-13    P1003.1b Shared Memory Functions
A-14    P1003.1b Semaphore Functions
A-15    POSIX 1003.1b Realtime Signal Functions
A-16    Signal Control and Other Signal Functions
A-17    sigsetops Primitives
A-18    Process Ownership Functions
A-19    Input and Output Functions
A-20    Device Control Functions
A-21    System Database Functions
 
Index