Silberschatz, Galvin and Gagne  Operating System Concepts Chapter 5: Threads Overview Multithreading Models Threading Issues Pthreads Solaris 2 Threads Windows 2000 Threads Linux Threads Java Threads

Silberschatz, Galvin and Gagne  Operating System Concepts PROCESS

Silberschatz, Galvin and Gagne  Operating System Concepts Single and Multithreaded Processes

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts BENEFITS

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts Remote Procedure Call Using Threads

Silberschatz, Galvin and Gagne  Operating System Concepts Remote Procedure Call Using Threads

Silberschatz, Galvin and Gagne  Operating System Concepts PROCESS VERSUS TREAD CONTEXT SWITCHING PER PROCESS ITEMS PER THREAD ITEMS Address spaceProgram counter Global variablesRegisters Open filesStack Child processesState Pending alarms Signals, signal handlers Accounting info

Silberschatz, Galvin and Gagne  Operating System Concepts THREAD STATES Spawn:New thread created Running, Ready: As before Block:Waiting for event. Do the mini-context switch i.e. save and restore registers, PC and SP Unblock:Change state to Ready Finish:Finish the thread within the process

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts Relationship Between Threads and Processes Threads:ProcessDescriptionExample Systems 1:1Each thread of execution is a unique process with its own address space and resources. Traditional UNIX implementations M:1 A process defines an address space and dynamic resource ownership. Multiple threads may be created and executed within that process. Windows NT, Solaris, OS/2, OS/390, MACH

Silberschatz, Galvin and Gagne  Operating System Concepts Relationship Between Threads and Processes Threads:ProcessDescriptionExample Systems 1:MA thread may migrate from one process environment to another. This allows a thread to be easily moved among distinct systems. Ra (Clouds), Emerald M:MCombines attributes of M:1 and 1:M cases TRIX

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts USER – LEVEL THREADS

Silberschatz, Galvin and Gagne  Operating System Concepts KERNEL – LEVEL THREADS

Silberschatz, Galvin and Gagne  Operating System Concepts User Threads Thread management done by user-level threads library Examples - POSIX Pthreads - Mach C-threads - Solaris threads

Silberschatz, Galvin and Gagne  Operating System Concepts Kernel Threads Supported by the Kernel Examples - Windows 95/98/NT/ Solaris - Tru64 UNIX - BeOS - Linux

Silberschatz, Galvin and Gagne  Operating System Concepts Multithreading Models Many-to-One One-to-One Many-to-Many

Silberschatz, Galvin and Gagne  Operating System Concepts Many-to-One Many user-level threads mapped to single kernel thread. Used on systems that do not support kernel threads.

Silberschatz, Galvin and Gagne  Operating System Concepts Many-to-One Model

Silberschatz, Galvin and Gagne  Operating System Concepts One-to-One Each user-level thread maps to kernel thread. Examples - Windows 95/98/NT/ OS/2

Silberschatz, Galvin and Gagne  Operating System Concepts One-to-one Model

Silberschatz, Galvin and Gagne  Operating System Concepts Many-to-Many Model Allows many user level threads to be mapped to many kernel threads. Allows the operating system to create a sufficient number of kernel threads. Solaris 2 Windows NT/2000 with the ThreadFiber package

Silberschatz, Galvin and Gagne  Operating System Concepts Many-to-Many Model

Silberschatz, Galvin and Gagne  Operating System Concepts Threading Issues Semantics of fork() and exec() system calls. Thread cancellation. Signal handling Thread pools Thread specific data

Silberschatz, Galvin and Gagne  Operating System Concepts Pthreads a POSIX standard (IEEE c) API for thread creation and synchronization. API specifies behavior of the thread library, implementation is up to development of the library. Common in UNIX operating systems.

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts /* example – cont. */

Silberschatz, Galvin and Gagne  Operating System Concepts Solaris 2 Threads

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts Solaris Process

Silberschatz, Galvin and Gagne  Operating System Concepts

Silberschatz, Galvin and Gagne  Operating System Concepts Solaris Thread Execution Synchronization Suspension Preemption Yielding

Silberschatz, Galvin and Gagne  Operating System Concepts Windows 2000 Threads Implements the one-to-one mapping. Each thread contains - a thread id - register set - separate user and kernel stacks - private data storage area

Silberschatz, Galvin and Gagne  Operating System Concepts Linux Threads Linux refers to them as tasks rather than threads. Thread creation is done through clone() system call. Clone() allows a child task to share the address space of the parent task (process)

Silberschatz, Galvin and Gagne  Operating System Concepts Java Threads Java threads may be created by:  Extending Thread class  Implementing the Runnable interface Java threads are managed by the JVM.

Silberschatz, Galvin and Gagne  Operating System Concepts Java Thread States