Download WindView for IRIX Programmer`s Guide

Glossary
pended state
A process is in the pended state if it attempted to obtain an object or resource
but the object or resource was not available; for example, if it made a call to
obtain a semaphore, but the semaphore was not available. A process in this
state is also known as a blocked process. See also process state, process state
transition.
preemption
If a process becomes ready to execute and it has a higher priority than the
currently executing process, the “new” process preempts the current
process. That is, the operating system saves the current process’s context and
switches to the context of the higher-priority process. See also process state
transition.
preemptive priority scheduling
In IRIX, each process is assigned a priority, and the kernel ensures that the
processor is allocated to the highest-priority ready process. The scheduling
is preemptive in that if a process of a higher priority than the executing
process becomes ready, the kernel preempts the current process and
switches to the higher-priority process. See also context switch, process state
transition.
priority
The standard IRIX scheduler provides 256 process priority levels, numbered
0 (highest) through 255 (lowest). Processes are assigned a priority when
created; however, while executing, a process may change its priority using
schedctl(2).
process
A process is an independent program in a IRIX application that has its own
job to perform, such as the management of a robot arm. Each process has its
own context, which is the processor environment and system resources the
process “sees” each time it is scheduled to run by the kernel. On a context
switch, a process’s context is saved. Processes can communicate and
synchronize with each other through interprocess communication
mechanisms (IPCs).
124