06-03-2003
In the UNIX environment a thread:
Exists within a process and uses the process resources.Its has its own independent flow of control as long as its parent process exists and the OS supports it .It May share the process resources with other threads that act equally independently (and dependently).It Dies if the parent process dies.
A thread can possess an independent flow of control and be schedulable because it maintains its own:
Stack pointer
Registers
Scheduling properties (such as policy or priority)
Set of pending and blocked signals
Thread specific data.
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LEARN ABOUT OSF1
pthread_attr_getscope
pthread_attr_getscope(3) Library Functions Manual pthread_attr_getscope(3)
NAME
pthread_attr_getscope - Obtains the contention scope attribute of the specified thread attributes object.
LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so)
SYNOPSIS
#include <pthread.h>
int pthread_attr_getscope(
const pthread_attr_t *attr,
int *scope);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
IEEE Std 1003.1c-1995, POSIX System Application Program Interface
PARAMETERS
Address of the thread attributes object whose contention scope attribute is obtained. Receives the value of the contention scope attribute
of the thread attributes object specified by attr.
DESCRIPTION
This routine obtains the value of the contention scope attribute of the thread attributes object specified in the attr argument and stores
it in the location specified by the scope argument. The specified attributes object must already be initialized at the time this routine
is called.
The contention scope attribute specifies the set of threads with which a thread must compete for processing resources. The contention
scope attribute specifies whether the new thread competes for processing resources only with other threads in its own process, called
process contention scope, or with all threads on the system, called system contention scope.
DECthreads selects at most one thread to execute on each processor at any point in time. DECthreads resolves the contention based on each
thread's scheduling attributes (for example, priority) and scheduling policy (for example, round-robin).
A thread created using a thread attributes object whose contention scope attribute is set to PTHREAD_SCOPE_PROCESS contends for processing
resources with other threads within its own process that also were created with PTHREAD_SCOPE_PROCESS. It is unspecified how such threads
are scheduled relative to threads in other processes or threads in the same process that were created with PTHREAD_SCOPE_SYSTEM contention
scope.
A thread created using a thread attributes object whose contention scope attribute is set to PTHREAD_SCOPE_SYSTEM contends for processing
resources with other threads in any process that also were created with PTHREAD_SCOPE_SYSTEM.
NOTES
The value of the contention scope attribute of a particular thread attributes object does not necessarily correspond to the actual schedul-
ing contention scope of any existing thread in your multithreaded program.
RETURN VALUES
If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:
Successful completion. The value specified by attr is not a valid thread attributes object. This routine is not supported by the imple-
mentation.
ERRORS
None
RELATED INFORMATION
Functions: pthread_attr_init(3), pthread_attr_setscope(3)
Manuals: Guide to DECthreads and Programmer's Guide
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pthread_attr_getscope(3)