2 cissp ® Official Study Guide Eighth Edition

Supervisory
The
supervisory state
is used when the process must perform an action that 
requires privileges that are greater than the problem state’s set of privileges, including 
modifying system confi guration, installing device drivers, or modifying security settings. 
Basically, any function not occurring in the user mode (ring 3) or problem state takes place 
in the supervisory mode. 
Stopped
When a process fi nishes or must be terminated (because an error occurs, a 
required resource is not available, or a resource request can’t be met), it goes into a
stopped 
state
. At this point, the operating system can recover all memory and other resources allo-
cated to the process and reuse them for other processes as needed. 
Figure 9.2 shows a diagram of how these various states relate to one another. New pro-
cesses always transition into the ready state. From there, ready processes always transition 
into the running state. While running, a process can transition into the stopped state if it 
completes or is terminated, return to the ready state for another time slice, or transition 
to the waiting state until its pending resource request is met. When the operating system 
decides which process to run next, it checks the waiting queue and the ready queue and 
takes the highest-priority job that’s ready to run (so that only waiting jobs whose pending 
requests have been serviced, or are ready to service, are eligible in this consideration). A 
special part of the kernel, called the
program executive
or the
process scheduler
, is always 
around (waiting in memory) so that when a process state transition must occur, it can step 
in and handle the mechanics involved. 

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Assess and Mitigate Security Vulnerabilities 
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F I g u r e 9 . 2
The process scheduler
Process needs
another
time slice
New processes
Ready
If CPU is available
Stopped
When process finishes,
or terminates
Unblocked
Running
Block for I/O,
resources
Waiting
In Figure 9.2 , the process scheduler manages the processes awaiting execution in the ready 
and waiting states and decides what happens to running processes when they transition 
into another state (ready, waiting, or stopped).