Process synchronization in os

Answer: b Explanation: When several processes access the same data concurrently and the outcome of the execution depends on the particular order in which access takes place is called race condition. 3. If a process is executing in its critical section, then no other processes can be executing in their critical section. What is this condition called? a) mutual exclusion b) critical exclusion c) synchronous exclusion d) asynchronous exclusion View Answer Answer: a Explanation: If a process is executing in its critical section, then no other processes can be executed in their critical section. This condition is called Mutual Exclusion. Critical section of the process is shared between multiple processes. If this section is executed by more than one or all of them concurrently then the outcome of this is not as per desired outcome. For this reason the critical section of the process should not be executed concurrently. Answer: c Explanation: Semaphore is a synchronization tool. Semaphore is a mechanism which synchronizes or controls access of threads on critical resources. There are two types of semaphores i) Binary Semaphore ii) Counting Semaphore. 5. A semaphore is a shared integer variable __________ a) that can not drop below zero b) that can not be more than zero c) that can not drop below one d) that can not be more than one View Answer Answer: a Explanation: A semaphore is a shared integer variable that can not drop below zero. In binary semaphore, if the value of the s...

Lecture Notes Week Topic Notes 1 Introduction to Operating Systems and Computer Systems/OS Structures Lecture set 1 (updated 4.7): [ 2 Processes, Threads, Interprocess Communication Lecture set 2 (updated 4.15): [ 3 CPU Scheduling Lecture set 3 (updated 4.15): [ 4 Process Synchronization Lecture set 4 (updated 4.24, tentative): [ Sample midterm Sample midterm: [ 5 Midterm review Slides (updated 5.5) : [ 6 Deadlocks Lecture set 5 (updated 5.18): [ 7 Memory Management: Part 1 Lecture set 6 part 1 (tentative): [ 8 Memory Management: Part 2 Lecture set 6 part 2 : [ 9 File Systems Lecture set 7 (tentative): [ Sample final Sample final: [ 10 Finals review Slides: [

In this tutorial, we’ll dive into a powerful and well-known process synchronization tool: semaphore. We’ll look into semaphore operations, types, and its implementation. Then we’ll explore some multi-threaded cases where the use of semaphores helps us with overcoming possible process synchronization problems. 2. What Is a Semaphore? A semaphore is an integer variable, shared among multiple processes. The main aim of using a semaphore is process synchronization and access control for a common resource in a concurrent environment. The initial value of a semaphore depends on the problem at hand. Usually, we use the number of resources available as the initial value. In the following sections, we’ll give more examples of initializing semaphores in different use cases. It’s a synchronization tool that does not require busy waiting. Hence, the operating system does not waste the CPU cycles when a process can’t operate due to a lack of access to a resource. A semaphore has two indivisible (atomic) operations, namely: and . These operations are sometimes referred to as and , or and in some contexts. In this article, let’s focus on semaphores implemented in the operating system kernel. Therefore, the and operations are implemented as system calls. Let be a semaphore, and its integer value represents the amount of some resource available. Now let’s examine how the operation works: The function simply decrements if it’s greater than zero (there are available resources to allocate). I...

This article needs additional citations for Please help Find sources: · · · · ( November 2014) ( In synchronization refers to one of two distinct but related concepts: synchronization of Process synchronization refers to the idea that multiple processes are to join up or The need for synchronization [ ] The need for synchronization does not arise merely in multi-processor systems but for any kind of concurrent processes; even in single processor systems. Mentioned below are some of the main needs for synchronization: Exclusive use resources: When multiple processes are dependent on a resource and they need to access it at the same time, the operating system needs to ensure that only one processor accesses it at a given point in time. This reduces concurrency. Thread or process synchronization [ ] Figure 1: Three processes accessing a shared resource ( Thread synchronization is defined as a mechanism which ensures that two or more concurrent For example, suppose that there are three processes, namely 1, 2, and 3. All three of them are concurrently executing, and they need to share a common resource (critical section) as shown in Figure 1. Synchronization should be used here to avoid any conflicts for accessing this shared resource. Hence, when Process 1 and 2 both try to access that resource, it should be assigned to only one process at a time. If it is assigned to Process 1, the other process (Process 2) needs to wait until Process 1 frees that resource (as shown in Figure...

Synchronization The presence of multiple threads in an application opens up potential issues regarding safe access to resources from multiple threads of execution. Two threads modifying the same resource might interfere with each other in unintended ways. For example, one thread might overwrite another’s changes or put the application into an unknown and potentially invalid state. If you are lucky, the corrupted resource might cause obvious performance problems or crashes that are relatively easy to track down and fix. If you are unlucky, however, the corruption may cause subtle errors that do not manifest themselves until much later, or the errors might require a significant overhaul of your underlying coding assumptions. When it comes to thread safety, a good design is the best protection you have. Avoiding shared resources and minimizing the interactions between your threads makes it less likely for those threads to interfere with each other. A completely interference-free design is not always possible, however. In cases where your threads must interact, you need to use synchronization tools to ensure that when they interact, they do so safely. OS X and iOS provide numerous synchronization tools for you to use, ranging from tools that provide mutually exclusive access to those that sequence events correctly in your application. The following sections describe these tools and how you use them in your code to affect safe access to your program’s resources. Synchronization...

Overview Monitor in an operating system is one method for achieving process synchronization. Programming languages help the monitor to accomplish mutual exclusion between different activities in a system. wait() and notify() constructs are synchronization functions that are available in the Java programming language. Scope In this article, we will see • Definition, syntax, and characteristics of a monitor in an operating system. • Components, advantages, and disadvantages of the monitor in an operating system. What is a monitor in OS? Monitors are a programming language component that aids in the regulation of shared data access. The Monitor is a package that contains shared data structures, operations, and synchronization between concurrent procedure calls. Therefore, a monitor is also known as a synchronization tool. Java, C#, Visual Basic, Ada, and concurrent Euclid are among some of the languages that allow the use of monitors. Processes operating outside the monitor can't access the monitor's internal variables, but they can call the monitor's procedures. For example, synchronization methods like the wait() and notify() constructs are available in the Java programming language. Syntax of monitor in OS Monitor in os has a simple syntax similar to how we define a class, it is as follows: Monitor in an operating system is simply a class containing variable_declarations, condition_variables, various procedures (functions), and an initializing_code block that is used for p...

This article needs additional citations for Please help Find sources: · · · · ( November 2014) ( In synchronization refers to one of two distinct but related concepts: synchronization of Process synchronization refers to the idea that multiple processes are to join up or The need for synchronization [ ] The need for synchronization does not arise merely in multi-processor systems but for any kind of concurrent processes; even in single processor systems. Mentioned below are some of the main needs for synchronization: Exclusive use resources: When multiple processes are dependent on a resource and they need to access it at the same time, the operating system needs to ensure that only one processor accesses it at a given point in time. This reduces concurrency. Thread or process synchronization [ ] Figure 1: Three processes accessing a shared resource ( Thread synchronization is defined as a mechanism which ensures that two or more concurrent For example, suppose that there are three processes, namely 1, 2, and 3. All three of them are concurrently executing, and they need to share a common resource (critical section) as shown in Figure 1. Synchronization should be used here to avoid any conflicts for accessing this shared resource. Hence, when Process 1 and 2 both try to access that resource, it should be assigned to only one process at a time. If it is assigned to Process 1, the other process (Process 2) needs to wait until Process 1 frees that resource (as shown in Figure...

In this tutorial, we’ll dive into a powerful and well-known process synchronization tool: semaphore. We’ll look into semaphore operations, types, and its implementation. Then we’ll explore some multi-threaded cases where the use of semaphores helps us with overcoming possible process synchronization problems. 2. What Is a Semaphore? A semaphore is an integer variable, shared among multiple processes. The main aim of using a semaphore is process synchronization and access control for a common resource in a concurrent environment. The initial value of a semaphore depends on the problem at hand. Usually, we use the number of resources available as the initial value. In the following sections, we’ll give more examples of initializing semaphores in different use cases. It’s a synchronization tool that does not require busy waiting. Hence, the operating system does not waste the CPU cycles when a process can’t operate due to a lack of access to a resource. A semaphore has two indivisible (atomic) operations, namely: and . These operations are sometimes referred to as and , or and in some contexts. In this article, let’s focus on semaphores implemented in the operating system kernel. Therefore, the and operations are implemented as system calls. Let be a semaphore, and its integer value represents the amount of some resource available. Now let’s examine how the operation works: The function simply decrements if it’s greater than zero (there are available resources to allocate). I...

Lecture Notes Week Topic Notes 1 Introduction to Operating Systems and Computer Systems/OS Structures Lecture set 1 (updated 4.7): [ 2 Processes, Threads, Interprocess Communication Lecture set 2 (updated 4.15): [ 3 CPU Scheduling Lecture set 3 (updated 4.15): [ 4 Process Synchronization Lecture set 4 (updated 4.24, tentative): [ Sample midterm Sample midterm: [ 5 Midterm review Slides (updated 5.5) : [ 6 Deadlocks Lecture set 5 (updated 5.18): [ 7 Memory Management: Part 1 Lecture set 6 part 1 (tentative): [ 8 Memory Management: Part 2 Lecture set 6 part 2 : [ 9 File Systems Lecture set 7 (tentative): [ Sample final Sample final: [ 10 Finals review Slides: [

Answer: b Explanation: When several processes access the same data concurrently and the outcome of the execution depends on the particular order in which access takes place is called race condition. 3. If a process is executing in its critical section, then no other processes can be executing in their critical section. What is this condition called? a) mutual exclusion b) critical exclusion c) synchronous exclusion d) asynchronous exclusion View Answer Answer: a Explanation: If a process is executing in its critical section, then no other processes can be executed in their critical section. This condition is called Mutual Exclusion. Critical section of the process is shared between multiple processes. If this section is executed by more than one or all of them concurrently then the outcome of this is not as per desired outcome. For this reason the critical section of the process should not be executed concurrently. Answer: c Explanation: Semaphore is a synchronization tool. Semaphore is a mechanism which synchronizes or controls access of threads on critical resources. There are two types of semaphores i) Binary Semaphore ii) Counting Semaphore. 5. A semaphore is a shared integer variable __________ a) that can not drop below zero b) that can not be more than zero c) that can not drop below one d) that can not be more than one View Answer Answer: a Explanation: A semaphore is a shared integer variable that can not drop below zero. In binary semaphore, if the value of the s...