Lifehacks

Is NSLock fair?

Is NSLock fair?

NSLock and the other Foundation’s locks are unfair, meaning that when a series of threads is waiting to acquire a lock, they will not acquire it in the same order in which they originally tried to lock it. A lower-level C pthread_mutex_t is also available in Swift.

What is os_ unfair_ lock?

The os_unfair_lock mutex (mutual exclusion) lock is currently the fastest lock in iOS. If your intention is to simply prevent two threads from accessing some piece of code at the same time (called a critical section) like in our EventQueue example, then this lock will get the job done with great performance.

What is NSRecursiveLock?

Overview. NSRecursiveLock defines a lock that may be acquired multiple times by the same thread without causing a deadlock, a situation where a thread is permanently blocked waiting for itself to relinquish a lock.

What is thread safe in iOS?

Thread safe is a concept in the context of multi-thread and it means any shared data is accessed by only one thread at any given time. If you want to write/read access to a shared resource from different threads, you should take the thread safety into consideration.

What is NSLock in Swift?

An object that coordinates the operation of multiple threads of execution within the same application.

What is race condition?

A race condition is an undesirable situation that occurs when a device or system attempts to perform two or more operations at the same time, but because of the nature of the device or system, the operations must be done in the proper sequence to be done correctly.

Is Swift dictionary thread-safe?

Dictionaries in Swift are not thread safe , they lead to wierd crashes which are very hard to debug. This class solves this problem by using a dictionary whose accesses are made thread safe by using a concurrent queue with a barrier.

Is Swift set thread-safe?

A code is called “Thread safe” if any shared data is accessed by only one thread at any given time. Notice these shared data are called critical sections in an operating system. The point is Swift collection types like Array and Dictionary are not thread-safe when declared mutable (With var keyword).

What is mutex in Swift?

Mutex — ensures that only one thread is active in a given region of code at a time. You can think of it as a semaphore with a maximum count of 1. Spinlock — causes a thread trying to acquire a lock to wait in a loop while checking if the lock is available.

How do I lock my mutex?

Use pthread_mutex_lock(3THR) to lock the mutex pointed to by mutex . When pthread_mutex_lock() returns, the mutex is locked and the calling thread is the owner. If the mutex is already locked and owned by another thread, the calling thread blocks until the mutex becomes available.

Is deadlock A race condition?

In this case, both threads will wait indefinitely for the resource held by the other thread. These threads are said to be deadlocked. Race conditions occur when two threads interact in a negatve (buggy) way depending on the exact order that their different instructions are executed.

What is race condition C#?

A race condition occurs when two or more threads are able to access shared data and they try to change it at the same time. Introduction. A race condition occurs when two or more threads are able to access shared data and they try to change it at the same time.