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Operating Systems Chapter 4
Terms from Chapter Four of Operating Systems Concepts by Galvin, Silberschatz, and Gagne
25
Computer Science
Undergraduate 3
02/10/2013
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Term
Heavyweight Process
 Definition
A process with a single thread of execution.
Term
Single-Threaded Process
 Definition
A process with only one thread. A thread is a unit of computer utilization, with a thread id, program counter, stack, and register set. It shares information with other threads in the same process.
Term
Multi-Threaded Process
 Definition
A process with more than one thread.
Term
User Threads
 Definition
Support for these kinds of threads are provided at the user level.
Term
Kernel Threads
 Definition
Threads supported by the kernel.
Term
Many-To-One Model
 Definition
One kernel thread to many user threads. Easy to do, but all will block if any block. Also can't run on multiple processors.
Term
One-To-One Model
 Definition
One kernel thread to each user thread. Fixed shortcomings of many-to-one, but means that creating each thread creates a kernel thread also which has more overhead than a user thread.
Term
Many-To-Many Model
 Definition
Many kernel threads support many more user threads. Seems to fix problems with one to one and many to one.
Term
Two-Level Model
 Definition
Like many-to-many, but allows one thread to bind to one kernel thread if it needs to.
Term
Thread Library
 Definition
Provides an API to programmers for creating and managing threads.
Term
Pthreads
 Definition
POSIX Standard for threads. Seen in C.
Term
Thread Cancellation
 Definition
Terminating a thread before it competes execution.
Term
Target Thread (for cancellation)
 Definition
The thread that is being cancelled.
Term
Asynchronous Cancellation
 Definition
One thread terminates the target thread. Can be messy, and usually is left as a last resort.
Term
Deferred Cancellation
 Definition
Threads periodically check whether they should terminate. Allows them to clean up after themselves.
Term
Cancellation Point
 Definition
Places in code execution where the thread checks if it needs to terminate.
Term
UNIX Signal
 Definition
A way UNIX systems let processes know that an event has occurred.
Term
Default Signal Handler
 Definition
The kernel level way of dealing with signals. May be overridden by user-defined handlers.
Term
User-Defined Signal Handler
 Definition
The programmer may choose to have the process do something when a signal is received. This overrides the default signal handler.
Term
Asynchronous Procedure Call (APC)
 Definition
A windows equivalent to UNIX signals except it goes to a particular thread rather than process.
Term
Thread Pool
 Definition
The list of all available threads. When one is needed, it is wakened by the system and begins execution.
Term
Thread-Specific data
 Definition
Data that only exists in a particular thread rather than in the entire process.
Term
Scheduler Activation
 Definition
Method of communication between user thread and kernel thread.
Term
Upcall
 Definition
The kernel letting the user thread know about a certain event that happens.
Term
Upcall Handler
 Definition
Thread library handles upcalls. Must be run on virtual processor.
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