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Chapter 4: Threads Operating System Concepts – th Edition Silberschatz, Galvin and Gagne ©2009 Chapter 4: Threads ■ Overview ■ Multithreading Models ■ Thread Libraries ■ Threading Issues ■ Operating System Examples ■ Windows XP Threads ■ Linux Threads Operating System Concepts – th Edition 4.2 Silberschatz, Galvin and Gagne ©2009 Objectives ■ To introduce the notion of a thread — a fundamental unit of CPU utilization that forms the basis of multithreaded computer systems ■ To discuss the APIs for the Pthreads, Win32, and Java thread libraries ■ To examine issues related to multithreaded programming Operating System Concepts – th Edition 4.3 Silberschatz, Galvin and Gagne ©2009 Motivation ■ Threads run within application ■ Multiple tasks with the application can be implemented by separate threads ● Update display ● Fetch data ● Spell checking ● Answer a network request ■ Process creation is heavy-weight while thread creation is light-weight ■ Can simplify code, increase efficiency ■ Kernels are generally multithreaded Operating System Concepts – th Edition 4.4 Silberschatz, Galvin and Gagne ©2009 Single and Multithreaded Processes Operating System Concepts – th Edition 4.5 Silberschatz, Galvin and Gagne ©2009 Benefits ■ Responsiveness ■ Resource Sharing ■ Economy ■ Scalability Operating System Concepts – th Edition 4.6 Silberschatz, Galvin and Gagne ©2009 Multicore Programming ■ Multicore systems putting pressure on programmers, challenges include: ● Dividing activities ● Balance ● Data splitting ● Data dependency ● Testing and debugging Operating System Concepts – th Edition 4.7 Silberschatz, Galvin and Gagne ©2009 Multithreaded Server Architecture Operating System Concepts – th Edition 4.8 Silberschatz, Galvin and Gagne ©2009 Concurrent Execution on a Single-core System Operating System Concepts – th Edition 4.9 Silberschatz, Galvin and Gagne ©2009 Parallel Execution on a Multicore System Operating System Concepts – th Edition 4.10 Silberschatz, Galvin and Gagne ©2009 Threading Issues ■ Semantics of fork() and exec() system calls ■ Thread cancellation of target thread ● ■ Asynchronous or deferred Signal handling ● Operating System Concepts – Synchronous and asynchronous th Edition 4.31 Silberschatz, Galvin and Gagne ©2009 Threading Issues (Cont.) ■ Thread pools ■ Thread-specific data ■ ■ Create Facility needed for data private to thread Scheduler activations Operating System Concepts – th Edition 4.32 Silberschatz, Galvin and Gagne ©2009 Semantics of fork() and exec() ■ Does fork() duplicate only the calling thread or all threads? Operating System Concepts – th Edition 4.33 Silberschatz, Galvin and Gagne ©2009 Thread Cancellation ■ Terminating a thread before it has finished ■ Two general approaches: ● Asynchronous cancellation terminates the target thread immediately ● Deferred cancellation allows the target thread to periodically check if it should be cancelled Operating System Concepts – th Edition 4.34 Silberschatz, Galvin and Gagne ©2009 Signal Handling ■ Signals are used in UNIX systems to notify a process that a particular event has occurred ■ A signal handler is used to process signals ■ Signal is generated by particular event Signal is delivered to a process Signal is handled Options: ●✎ Deliver the signal to the thread to which the signal applies ●✎ Deliver the signal to every thread in the process ●✎ Deliver the signal to certain threads in the process ●✎ Assign a specific thread to receive all signals for the process Operating System Concepts – th Edition 4.35 Silberschatz, Galvin and Gagne ©2009 Thread Pools ■ Create a number of threads in a pool where they await work ■ Advantages: ● Usually slightly faster to service a request with an existing thread than create a new thread ● Allows the number of threads in the application(s) to be bound to the size of the pool Operating System Concepts – th Edition 4.36 Silberschatz, Galvin and Gagne ©2009 Thread Specific Data ■ Allows each thread to have its own copy of data ■ Useful when you not have control over the thread creation process (i.e., when using a thread pool) Operating System Concepts – th Edition 4.37 Silberschatz, Galvin and Gagne ©2009 Scheduler Activations ■ Both M:M and Two-level models require communication to maintain the appropriate number of kernel threads allocated to the application ■ Scheduler activations provide upcalls - a communication mechanism from the kernel to the thread library ■ This communication allows an application to maintain the correct number kernel threads Operating System Concepts – th Edition 4.38 Silberschatz, Galvin and Gagne ©2009 Lightweight Processes Operating System Concepts – th Edition 4.39 Silberschatz, Galvin and Gagne ©2009 Operating System Examples ■ Windows XP Threads ■ Linux Thread Operating System Concepts – th Edition 4.40 Silberschatz, Galvin and Gagne ©2009 Windows XP Threads Data Structures Operating System Concepts – th Edition 4.41 Silberschatz, Galvin and Gagne ©2009 Windows XP Threads ■ Implements the one-to-one mapping, kernel-level ■ Each thread contains ● A thread id ● Register set ● Separate user and kernel stacks ● Private data storage area ■ The register set, stacks, and private storage area are known as the context of the threads ■ The primary data structures of a thread include: ● ETHREAD (executive thread block) ● KTHREAD (kernel thread block) ● TEB (thread environment block) Operating System Concepts – th Edition 4.42 Silberschatz, Galvin and Gagne ©2009 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) ■ struct task_struct points to process data structures (shared or unique) Operating System Concepts – th Edition 4.43 Silberschatz, Galvin and Gagne ©2009 Linux Threads ■ fork() and clone() system calls ■ Doesn’t distinguish between process and thread ■ Uses term task rather than thread ■ clone() takes options to determine sharing on process create ■ struct task_struct points to process data structures (shared or unique) Operating System Concepts – th Edition 4.44 Silberschatz, Galvin and Gagne ©2009 End of Chapter Operating System Concepts – th Edition Silberschatz, Galvin and Gagne ©2009 [...]...User Threads ■ Thread management done by user-level threads library ■ Three primary thread libraries: ● POSIX Pthreads ● Win32 threads ● Java threads Operating System Concepts – 8 th Edition 4. 11 Silberschatz, Galvin and Gagne ©2009 Kernel Threads ■ Supported by the Kernel ■ Examples ● Windows XP/2000 ● Solaris ● Linux ● Tru 64 UNIX ● Mac OS X Operating System Concepts – 8 th Edition 4. 12 Silberschatz,... Many-to-Many Operating System Concepts – 8 th Edition 4. 13 Silberschatz, Galvin and Gagne ©2009 Many-to-One ■ Many user-level threads mapped to single kernel thread ■ Examples: ● Solaris Green Threads ● GNU Portable Threads Operating System Concepts – 8 th Edition 4. 14 Silberschatz, Galvin and Gagne ©2009 Many-to-One Model Operating System Concepts – 8 th Edition 4. 15 Silberschatz, Galvin and Gagne ©2009 One-to-One... Operating System Concepts – 8 th Edition 4. 23 Silberschatz, Galvin and Gagne ©2009 Pthreads Example Operating System Concepts – 8 th Edition 4. 24 Silberschatz, Galvin and Gagne ©2009 Pthreads Example (Cont.) Operating System Concepts – 8 th Edition 4. 25 Silberschatz, Galvin and Gagne ©2009 Win32 API Multithreaded C Program Operating System Concepts – 8 th Edition 4. 26 Silberschatz, Galvin and Gagne ©2009... (Cont.) Operating System Concepts – 8 th Edition 4. 27 Silberschatz, Galvin and Gagne ©2009 Java Threads ■ Java threads are managed by the JVM ■ Typically implemented using the threads model provided by underlying OS ■ Java threads may be created by: ● Extending Thread class ● Implementing the Runnable interface Operating System Concepts – 8 th Edition 4. 28 Silberschatz, Galvin and Gagne ©2009 Java Multithreaded... and later Operating System Concepts – 8 th Edition 4. 16 Silberschatz, Galvin and Gagne ©2009 One-to-one Model Operating System Concepts – 8 th Edition 4. 17 Silberschatz, Galvin and Gagne ©2009 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 prior to version 9 ■ Windows NT/2000... System Concepts – 8 th Edition 4. 18 Silberschatz, Galvin and Gagne ©2009 Many-to-Many Model Operating System Concepts – 8 th Edition 4. 19 Silberschatz, Galvin and Gagne ©2009 Two-level Model ■ Similar to M:M, except that it allows a user thread to be bound to kernel thread ■ Examples ● IRIX ● HP-UX ● Tru 64 UNIX ● Solaris 8 and earlier Operating System Concepts – 8 th Edition 4. 20 Silberschatz, Galvin and... Operating System Concepts – 8 th Edition 4. 21 Silberschatz, Galvin and Gagne ©2009 Thread Libraries ■ Thread library provides programmer with API for creating and managing threads ■ Two primary ways of implementing ● Library entirely in user space ● Kernel-level library supported by the OS Operating System Concepts – 8 th Edition 4. 22 Silberschatz, Galvin and Gagne ©2009 Pthreads ■ May be provided either as... to certain threads in the process ●✎ Assign a specific thread to receive all signals for the process Operating System Concepts – 8 th Edition 4. 35 Silberschatz, Galvin and Gagne ©2009 Thread Pools ■ Create a number of threads in a pool where they await work ■ Advantages: ● Usually slightly faster to service a request with an existing thread than create a new thread ● Allows the number of threads in... Create Facility needed for data private to thread Scheduler activations Operating System Concepts – 8 th Edition 4. 32 Silberschatz, Galvin and Gagne ©2009 Semantics of fork() and exec() ■ Does fork() duplicate only the calling thread or all threads? Operating System Concepts – 8 th Edition 4. 33 Silberschatz, Galvin and Gagne ©2009 Thread Cancellation ■ Terminating a thread before it has finished ■ Two... th Edition 4. 29 Silberschatz, Galvin and Gagne ©2009 Java Multithreaded Program (Cont.) Operating System Concepts – 8 th Edition 4. 30 Silberschatz, Galvin and Gagne ©2009 Threading Issues ■ Semantics of fork() and exec() system calls ■ Thread cancellation of target thread ● ■ Asynchronous or deferred Signal handling ● Operating System Concepts – 8 Synchronous and asynchronous th Edition 4. 31 Silberschatz, ... user-level threads library ■ Three primary thread libraries: ● POSIX Pthreads ● Win32 threads ● Java threads Operating System Concepts – th Edition 4. 11 Silberschatz, Galvin and Gagne ©2009 Kernel Threads. .. Windows XP Threads ■ Linux Thread Operating System Concepts – th Edition 4. 40 Silberschatz, Galvin and Gagne ©2009 Windows XP Threads Data Structures Operating System Concepts – th Edition 4. 41 Silberschatz,... System Concepts – th Edition 4. 23 Silberschatz, Galvin and Gagne ©2009 Pthreads Example Operating System Concepts – th Edition 4. 24 Silberschatz, Galvin and Gagne ©2009 Pthreads Example (Cont.) Operating

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