What is a race condition explain with example?
A race condition occurs when a software program depends on the timing of one or more processes to function correctly. If a program relies on threads that run in an unpredictable sequence, a race condition may occur. A simple example is a logic gate that handles boolean values.
What is race condition in computer science?
A race condition or race hazard is the condition of an electronics, software, or other system where the system’s substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable.
What is the difference between race condition and deadlock?
A deadlock is when two (or more) threads are blocking each other. Usually this has something to do with threads trying to acquire shared resources. Race conditions occur when two threads interact in a negatve (buggy) way depending on the exact order that their different instructions are executed.
How race condition occur in operating system?
A race condition is a situation that may occur inside a critical section. This happens when the result of multiple thread execution in critical section differs according to the order in which the threads execute.
Why Semaphore is used in OS?
Semaphores are integer variables that are used to solve the critical section problem by using two atomic operations, wait and signal that are used for process synchronization. The wait operation decrements the value of its argument S, if it is positive. If S is negative or zero, then no operation is performed.
How can deadlock be prevented?
7.4 Deadlock Prevention
- 7.4.1 Mutual Exclusion. Shared resources such as read-only files do not lead to deadlocks.
- 2 Hold and Wait. To prevent this condition processes must be prevented from holding one or more resources while simultaneously waiting for one or more others.
- 3 No Preemption.
- 4 Circular Wait.
How can deadlocks be resolved?
Two processes competing for two resources in opposite order. A deadlock occurs when the first process locks the first resource at the same time as the second process locks the second resource. The deadlock can be resolved by cancelling and restarting the first process.
What is deadlock and how we can prevent it?
In order to avoid deadlock, you have to acquire a lock in the fixed order. Once process1 commits the transaction successfully, it will release the locks on the resources; therefore process 2 will get the required resources in order to complete the transaction successfully without getting into the deadlock.
How deadlocks are detected?
In this case for Deadlock detection we can run an algorithm to check for cycle in the Resource Allocation Graph. Presence of cycle in the graph is the sufficient condition for deadlock. In the above diagram, resource 1 and resource 2 have single instances. There is a cycle R1 → P1 → R2 → P2.
What is the best action a system can take when deadlock is detected?
You can: Interrupt (i.e. send a signal/exception to) all the threads holding the lock. They will have to be able to handle the resulting interrupt, though. Kill all the threads/processes involved.
What is deadlock example?
A deadlock is a condition where a program cannot access a resource it needs to continue. For example, the following situation will cause a deadlock between two processes: Process 1 requests resource B from process 2. Resource B is locked while process 2 is running.
Why do we use banker’s algorithm?
Banker’s Algorithm is used majorly in the banking system to avoid deadlock. It helps you to identify whether a loan will be given or not. This algorithm is used to test for safely simulating the allocation for determining the maximum amount available for all resources.
What is safe state in banker’s algorithm?
By using the Banker’s algorithm, the bank ensures that when customers request money the bank never leaves a safe state. If the customer’s request does not cause the bank to leave a safe state, the cash will be allocated, otherwise the customer must wait until some other customer deposits enough.
What is Banker’s algorithm with example?
The banker’s algorithm is a resource allocation and deadlock avoidance algorithm that tests for safety by simulating the allocation for predetermined maximum possible amounts of all resources, then makes an “s-state” check to test for possible activities, before deciding whether allocation should be allowed to continue …
What is the drawback of Banker’s algorithm?
Disadvantages of the Banker’s Algorithm It requires the number of processes to be fixed; no additional processes can start while it is executing. It requires that the number of resources remain fixed; no resource may go down for any reason without the possibility of deadlock occurring.
How do you calculate Banker’s algorithm?
Suppose n is the number of processes, and m is the number of each type of resource used in a computer system. Available: It is an array of length ‘m’ that defines each type of resource available in the system. When Available[j] = K, means that ‘K’ instances of Resources type R[j] are available in the system.
What is FIFO algorithm?
The simplest page-replacement algorithm is a FIFO algorithm. The first-in, first-out (FIFO) page replacement algorithm is a low-overhead algorithm that requires little bookkeeping on the part of the operating system. In simple words, on a page fault, the frame that has been in memory the longest is replaced.
Which data structure is used in banker’s algorithm?
Data Structures used to implement Banker’s Algorithm Max: It is a 2-D array that tells the maximum number of each resource type required by a process for successful execution. Example: Max[P1][R1] = A, specifies that the process P1 needs a maximum of A instances of resource R1 for complete execution.
Which algorithm is used to avoid deadlock?
Overview
| Name | Coffman conditions | Description |
|---|---|---|
| Banker’s algorithm | Mutual exclusion | The Banker’s algorithm is a resource allocation and deadlock avoidance algorithm developed by Edsger Dijkstra. |
| Preventing recursive locks | Mutual exclusion | This prevents a single thread from entering the same lock more than once. |
What is the formula for need Matrix?
It is a two-dimensional array. It is an n x m matrix which indicates the remaining resource needs of each process. If Need[i][j] = k , then process Pi may need k more instances of resource type Rj to complete its task.
What is the content of need Matrix?
Need matrix is a matrix which contains the maximum need of the processes and the need matrix for the above example is given below: b.
Is the system in safe state?
A system is in a safe state only if there exists a safe sequence of processes P1, P2, , Pn where: For each Pi, the resources that Pi can still request can be satisfied by the currently available resources plus the resources help by all Pj, j
What is safety algorithm?
What are the four necessary conditions for characterizing deadlock?
Four Necessary and Sufficient Conditions for Deadlock
- mutual exclusion. The resources involved must be unshareable; otherwise, the processes would not be prevented from using the resource when necessary.
- hold and wait or partial allocation.
- no pre-emption.
- resource waiting or circular wait.
What is starvation OS?
Starvation is the problem that occurs when high priority processes keep executing and low priority processes get blocked for indefinite time. In heavily loaded computer system, a steady stream of higher-priority processes can prevent a low-priority process from ever getting the CPU.
What is Ostrich Algorithm in OS?
In computer science, the ostrich algorithm is a strategy of ignoring potential problems on the basis that they may be exceedingly rare. It is named for the ostrich effect which is defined as “to stick one’s head in the sand and pretend there is no problem”.
What is ostrich approach?
New Word Suggestion. A person who refuses to face reality or recognize the truth. A reference to the popular notion that the ostrich hides from danger by burying its head in the sand.
What is deadlock avoidance in OS?
In deadlock avoidance, the request for any resource will be granted if the resulting state of the system doesn’t cause deadlock in the system. In order to avoid deadlocks, the process must tell OS, the maximum number of resources a process can request to complete its execution. …
What is deadlock ignorance?
Deadlock Ignorance is the most widely used approach among all the mechanism. This is being used by many operating systems mainly for end user uses. In this approach, the Operating system assumes that deadlock never occurs. In these types of systems, the user has to simply restart the computer in the case of deadlock.