Chapter 4 Threads Chapter 4 Threads n Overview

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Chapter 4: Threads

Chapter 4: Threads

Chapter 4: Threads n Overview n Multithreading Models n Threading Issues n Pthreads n

Chapter 4: Threads n Overview n Multithreading Models n Threading Issues n Pthreads n Windows XP Threads n Linux Threads n Java Threads Operating System Concepts – 7 th edition, Jan 23, 2005 4. 2 Silberschatz, Galvin and Gagne © 2005

Single and Multithreaded Processes Operating System Concepts – 7 th edition, Jan 23, 2005

Single and Multithreaded Processes Operating System Concepts – 7 th edition, Jan 23, 2005 4. 3 Silberschatz, Galvin and Gagne © 2005

Benefits n Responsiveness n Resource Sharing n Economy n Utilization of MP Architectures Operating

Benefits n Responsiveness n Resource Sharing n Economy n Utilization of MP Architectures Operating System Concepts – 7 th edition, Jan 23, 2005 4. 4 Silberschatz, Galvin and Gagne © 2005

Thread Libraries n Thread management done by user-level or system-level thread library n Three

Thread Libraries n Thread management done by user-level or system-level thread library n Three primary thread libraries: l POSIX Pthreads (Fig 4. 6) l Win 32 threads (Fig 4. 7) l Java threads (next slide) Operating System Concepts – 7 th edition, Jan 23, 2005 4. 5 Silberschatz, Galvin and Gagne © 2005

Java Threads n Java threads are managed by the JVM n Java threads may

Java Threads n Java threads are managed by the JVM n Java threads may be created by: Extending Thread class l Implementing the Runnable interface n Figure 4. 8 n p. 138 l Operating System Concepts – 7 th edition, Jan 23, 2005 4. 6 Silberschatz, Galvin and Gagne © 2005

Kernel Threads n Supported by the Kernel n Examples l Windows XP/2000 l Solaris

Kernel Threads n Supported by the Kernel n Examples l Windows XP/2000 l Solaris l Linux l Tru 64 UNIX l Mac OS X Operating System Concepts – 7 th edition, Jan 23, 2005 4. 7 Silberschatz, Galvin and Gagne © 2005

Multithreading Models n Many-to-One n One-to-One n Many-to-Many Operating System Concepts – 7 th

Multithreading Models n Many-to-One n One-to-One n Many-to-Many Operating System Concepts – 7 th edition, Jan 23, 2005 4. 8 Silberschatz, Galvin and Gagne © 2005

Many-to-One n Many user-level threads mapped to single kernel thread n Examples: l Green

Many-to-One n Many user-level threads mapped to single kernel thread n Examples: l Green Threads (avail. for Solaris) l GNU Portable Threads Operating System Concepts – 7 th edition, Jan 23, 2005 4. 9 Silberschatz, Galvin and Gagne © 2005

Many-to-One Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 10

Many-to-One Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 10 Silberschatz, Galvin and Gagne © 2005

One-to-One n Each user-level thread maps to kernel thread n Examples l Windows NT/XP/2000/XP

One-to-One n Each user-level thread maps to kernel thread n Examples l Windows NT/XP/2000/XP l Linux l Solaris 9 and later Operating System Concepts – 7 th edition, Jan 23, 2005 4. 11 Silberschatz, Galvin and Gagne © 2005

One-to-one Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 12

One-to-one Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 12 Silberschatz, Galvin and Gagne © 2005

Many-to-Many Model n Allows many user level threads to be mapped to many kernel

Many-to-Many Model n Allows many user level threads to be mapped to many kernel threads n Allows the operating system to create a sufficient number of kernel threads n Solaris prior to version 9 n Windows NT/2000 with the Thread. Fiber package Operating System Concepts – 7 th edition, Jan 23, 2005 4. 13 Silberschatz, Galvin and Gagne © 2005

Many-to-Many Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 14

Many-to-Many Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 14 Silberschatz, Galvin and Gagne © 2005

Two-level Model n Similar to M: M, except that it allows a user thread

Two-level Model n Similar to M: M, except that it allows a user thread to be bound to kernel thread n Examples l IRIX l HP-UX l Tru 64 UNIX l Solaris 8 and earlier Operating System Concepts – 7 th edition, Jan 23, 2005 4. 15 Silberschatz, Galvin and Gagne © 2005

Two-level Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 16

Two-level Model Operating System Concepts – 7 th edition, Jan 23, 2005 4. 16 Silberschatz, Galvin and Gagne © 2005

Threading Issues n Semantics of fork() and exec() system calls n Thread cancellation n

Threading Issues n Semantics of fork() and exec() system calls n Thread cancellation n Signal handling n Thread pools n Thread specific data n Scheduler activations Operating System Concepts – 7 th edition, Jan 23, 2005 4. 17 Silberschatz, Galvin and Gagne © 2005

Semantics of fork() and exec() n Does fork() duplicate only the calling thread or

Semantics of fork() and exec() n Does fork() duplicate only the calling thread or all threads? Operating System Concepts – 7 th edition, Jan 23, 2005 4. 18 Silberschatz, Galvin and Gagne © 2005

Thread Cancellation n Terminating a thread (target thread) before it has finished. n What

Thread Cancellation n Terminating a thread (target thread) before it has finished. n What happens to the resources of the thread? Shared data being updated? n Two general approaches: l Asynchronous cancellation terminates the target thread immediately l Deferred cancellation allows the target thread to periodically check if it should be cancelled, at safe and appropriate cancellation points. Operating System Concepts – 7 th edition, Jan 23, 2005 4. 19 Silberschatz, Galvin and Gagne © 2005

Signal Handling n Signals are used in UNIX systems to notify a process that

Signal Handling n Signals are used in UNIX systems to notify a process that a particular event has occurred n A signal handler is used to process signals n 1. Signal is generated by particular event 2. Signal is delivered to a process 3. Signal is handled Options: l Deliver the signal to the thread to which the signal applies l Deliver the signal to every thread in the process l Deliver the signal to certain threads in the process l Assign a specific thread to receive all signals for the process Operating System Concepts – 7 th edition, Jan 23, 2005 4. 20 Silberschatz, Galvin and Gagne © 2005

Thread Pools n Create a number of threads in a pool where they await

Thread Pools n Create a number of threads in a pool where they await work n Advantages: l Usually slightly faster to service a request with an existing thread than create a new thread l Allows the number of threads in the application(s) to be bound to the size of the pool l In advanced thread pools, the size of the pool can be adjusted dynamically Operating System Concepts – 7 th edition, Jan 23, 2005 4. 21 Silberschatz, Galvin and Gagne © 2005

Thread Specific Data n Allows each thread to have its own copy of data

Thread Specific Data n Allows each thread to have its own copy of data n Useful when you do not have control over the thread creation process (i. e. , when using a thread pool) n Most thread libraries, incl. Win 32, Pthreads & Java, all support thread specific data Operating System Concepts – 7 th edition, Jan 23, 2005 4. 22 Silberschatz, Galvin and Gagne © 2005

Scheduler Activations n Both M: M and Two-level models require communication to maintain the

Scheduler Activations n Both M: M and Two-level models require communication to maintain the appropriate number of kernel threads allocated to the application n Scheduler activations provide upcalls - a communication mechanism from the kernel to the thread library n This communication allows an application to maintain the correct number kernel threads Operating System Concepts – 7 th edition, Jan 23, 2005 4. 23 Silberschatz, Galvin and Gagne © 2005

Pthreads n A POSIX standard (IEEE 1003. 1 c) API for thread creation and

Pthreads n A POSIX standard (IEEE 1003. 1 c) API for thread creation and synchronization n API specifies behavior of the thread library, implementation is up to development of the library n Common in UNIX operating systems (Solaris, Linux, Mac OS X) Operating System Concepts – 7 th edition, Jan 23, 2005 4. 24 Silberschatz, Galvin and Gagne © 2005

Windows XP Threads n Win 32 API implements the one-to-one mapping, Also provides fiber

Windows XP Threads n Win 32 API implements the one-to-one mapping, Also provides fiber library for many to many mapping. n Each thread contains l A thread id l Register set l Separate user and kernel stacks l Private data storage area n The register set, stacks, and private storage area are known as the context of the threads n The primary data structures of a thread (Fig. 4. 10) include: ETHREAD (executive thread block) l KTHREAD (kernel thread block) l TEB (thread environment block) l Operating System Concepts – 7 th edition, Jan 23, 2005 4. 25 Silberschatz, Galvin and Gagne © 2005

Linux Threads n Linux refers to them (flows of control within programs) as tasks

Linux Threads n Linux refers to them (flows of control within programs) as tasks rather than threads or processes n Thread creation is done through clone() system call n clone() allows a child task to share the address space of the parent task (process) Operating System Concepts – 7 th edition, Jan 23, 2005 4. 26 Silberschatz, Galvin and Gagne © 2005

Java Thread States Operating System Concepts – 7 th edition, Jan 23, 2005 4.

Java Thread States Operating System Concepts – 7 th edition, Jan 23, 2005 4. 27 Silberschatz, Galvin and Gagne © 2005

End of Chapter 4

End of Chapter 4

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