30 Questions
What is the primary concern of Operating System design?
Management of processes and threads
What is the main difficulty in managing concurrent processing?
Sharing of global resources among processes
In a uniprocessor system, what makes it difficult to predict the relative speed of execution of processes?
The activities of other processes
What is the outcome of a race condition in concurrent processing?
The process that updates last determines the final value of the variable
What is the main challenge in debugging concurrent programs?
The results are not deterministic and reproducible
What is the main concern of Operating System design in terms of concurrency?
To design and manage concurrent processing
What is a fundamental requirement for processes to interact with each other?
Synchronization and communication
What is the purpose of semWait and semSignal operations in implementing semaphores?
To ensure atomicity
What is a characteristic of a non-blocking send in message passing?
The sender continues on without waiting for the message to be delivered
What is the purpose of the receive primitive in message passing?
To receive information from another process
What is an approach to providing both synchronization and communication between processes?
Message Passing
Why is it imperative to implement semWait and semSignal operations as atomic primitives?
To guarantee the correctness of the semaphore implementation
What is the primary purpose of a semaphore?
To ensure mutual exclusion in a multi-process environment
Which of the following is a characteristic of a strong semaphore?
The process that has been blocked the longest is released from the queue first
In the producer/consumer problem, what is the primary constraint on the buffer?
Only one producer or consumer can access the buffer at any one time
What is the primary goal of allocating and de-allocating resources for each active process?
To protect the data and physical resources of each process against interference by other processes
What is the consequence of decrementing a semaphore in a uniprocessor system?
It is unknown whether the process will block or not
What is the primary function of the semWait operation?
To decrement the value of the semaphore
What is the primary reason why concurrent processes come into conflict?
Because of competition for use of the same resource
What is the purpose of the queue in a semaphore implementation?
To hold the processes waiting on the semaphore
What is the primary goal of implementing mutual exclusion?
To prevent a process from being denied access to a critical section when there is no other process using it
What is the drawback of disabling interrupts to guarantee mutual exclusion in a uniprocessor system?
It may degrade the efficiency of execution
What is the Compare&Swap Instruction used for?
To compare and exchange values in a memory
What is the main advantage of using Special Machine Instructions for mutual exclusion?
It can be carried out atomically
What is the primary goal of a nonblocking send operation?
To allow the sender to continue processing without waiting
In direct addressing, how is the source of the message typically identified?
Through an implicit source parameter in the receive primitive
What is the primary benefit of using indirect addressing in message passing?
Greater flexibility in the use of messages
In a message passing system, what is the purpose of a mailbox?
To provide a shared data structure for multiple processes
What is a common problem in concurrent processing that can be addressed using message passing?
Mutual exclusion
Which type of process exists solely to provide a service or resource to other processes?
Service process
Study Notes
Operating System Design and Concurrency
- Operating System design is concerned with the management of processes and threads
- Multiple applications are invented to allow processing time to be shared among active applications
- Structured Applications are an extension of modular design and structured programming
Operating System Structure
- Operating Systems themselves are implemented as a set of processes or threads
- Interleaving and overlapping can be viewed as examples of concurrent processing
Difficulties of Concurrency
- Sharing of global resources
- Difficulty for the OS to manage the allocation of resources optimally
- Difficulty in locating programming errors as results are not deterministic and reproducible
- Occurs when multiple processes or threads read and write data items
- The final result depends on the order of execution
Operating System Concerns
- Design and management issues raised by the existence of concurrency
- The OS must be able to:
- Manage the allocation of resources
- Prevent interference between processes
- Ensure that the processes and outputs are independent of the processing speed
Mutual Exclusion
- Mutual exclusion is necessary to ensure that only one process or thread can access a shared resource at a time
- Implemented using binary semaphores or other mechanisms
- A solution to the bounded-buffer producer/consumer problem using semaphores is shown in Figure 5.13
Semaphores
- A semaphore is a variable that has an integer value upon which only three operations are defined:
- Initialize to a nonnegative integer value
- Decrement the value (semWait)
- Increment the value (semSignal)
- There is no way to inspect or manipulate semaphores other than these three operations
- Consequences of using semaphores:
- No way to know before a process decrements a semaphore whether it will block or not
- No way to know which process will continue immediately on a uniprocessor system when two processes are running concurrently
- Don't know whether another process is waiting, so the number of unblocked processes may be zero or one
Message Passing
- Message passing is one approach to providing both synchronization and communication
- Works with distributed systems and shared memory multiprocessor and uniprocessor systems
- The actual function is normally provided in the form of a pair of primitives:
- send (destination, message)
- receive (source, message)
- A process sends information in the form of a message to another process designated by a destination
- A process receives information by executing the receive primitive, indicating the source and the message
- Both sender and receiver are blocked until the message is delivered
Non-Blocking Send and Receive
- Non-blocking send, blocking receive: sender continues on but receiver is blocked
- Non-blocking send, non-blocking receive: neither party is required to wait
Mutual Exclusion Using Message Passing
- A solution to the bounded-buffer producer/consumer problem using messages is shown in Figure 5.21
Readers/Writers Problem
- A data area is shared among many processes
- Some processes only read the data area (readers) and some only write to the data area (writers)
- Conditions that must be satisfied:
- No reader can access the data area while a writer is accessing it
- No writer can access the data area while a reader is accessing it
- No writer can access the data area while another writer is accessing it
Test your knowledge on Operating System design principles, focusing on concurrency, mutual exclusion, and synchronization. Learn about multiprogramming, multiprocessing, and distributed processing in this chapter 5 quiz from William Stallings' Seventh Edition.
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