Page 150 - DCAP103_Principle of operating system

Unit 4: Process Management-III

7. Which is not the state of the process? Notes
( a) Blocked (b) Running
( c) Ready (d) Privileged
Fill in the blanks:

8. .................. is a lightweight unit of program execution.
9. An example of a discretionary acess control is a .................. .
10. A system is in a safe state only if there exists a .................. .

4.7 Summary

• If a data item is shared by a number threads, race conditions could occur if the shared
item is not protected properly.
• The first restriction is only the owner can release the lock. The second restriction is recursive
lock acquisition is not allowed.
• Each process has a code segment, called critical section, in which the shared data is accessed.
• For many years, microprocessors have included on-chip memory management units
(MMU).
• As applications become more complex, performing more functions for a software-hungry
world, the number of bugs in fielded systems will continue to rise.
• A typical embedded system has several types of interrupts resulting from the use of
various kinds of devices.
• Priority inversion has long been the bane of system designers attempting to perform rate
monotonic analysis, since RMA depends on higher priority threads running before lower
priority threads.
• A semaphore is a protected variable whose value can be accessed and altered only by the
operations P and V and initialization operation called ‘Semaphoiinitislize’.
• Deadlocks can be described more precisely in terms of a directed graph called a system
resource-allocation graph.

4.8 Keywords

Memory Management Unit (MMU): Memory management units that enable individual threads
of software to run in hardware-protected address spaces.
Real Time Operating System (RTOS): A Real-Time Operating System is a computing environment
that reacts to input within a specific time period.
Rate Monotonic Analysis (RMA): Rate monotonic analysis is frequently used by system designers
to analyze and predict the timing behavior of systems.
Deadlock: A deadlock is a situation in which two computer programs sharing the same resource
are effectively preventing each other from accessing the resource, resulting in both programs
ceasing to function.
Resource Allocation Graph: Deadlocks can be described more precisely in terms of a directed
graph called a system resource-allocation graph.
Deadlock Avoidance: A deadlock-avoidance algorithm dynamically examines the resource-
allocation state to ensure that a circular wait condition can never exist.
Claim Edge: Resource-allocation graph can be used for deadlock avoidance. In addition to the
request and assignment edges, we introduce a new type of edge, called a claim edge.

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