读写锁饥饿问题

说明

读写分离锁：将读操作和写操作分离，使用不同的锁进行控制。读锁可以允许多个线程同时读取数据，写锁则只允许一个线程进行写操作。这样就可以避免写操作对读操作的饥饿，同时也避免读操作对写操作的饥饿。

公平锁：公平锁会按照请求的顺序分配锁，确保每个线程都有机会获取锁，避免某些线程一直无法获取锁的情况。但是使用公平锁会降低并发性能，因为每个线程都需要等待前面的线程释放锁才能获取锁。

优先级锁：优先级锁会根据线程的优先级分配锁，优先级高的线程会先获取锁。但是使用优先级锁会存在优先级反转的问题，即低优先级的线程可能会一直无法获取锁，因为高优先级的线程一直占用锁。

重入锁：重入锁允许同一个线程多次获取锁，从而避免了同一个线程对其他线程的饥饿。但是如果一个线程多次获取锁而没有释放锁，就会导致死锁。

自旋锁：自旋锁会让线程不断地尝试获取锁，而不是阻塞等待锁的释放。这样可以避免线程的上下文切换，从而提高并发性能。但是如果锁被占用的时间过长，自旋锁会导致CPU资源的浪费。

总之，解决锁的读饥饿和写饥饿的方法有很多种，需要根据具体的应用场景选择合适的方法。同时，还需要注意锁的使用方式和锁的粒度，避免出现锁的竞争和饥饿问题。

读写锁示例

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class ReadWriteLockDemo {
    
    
    private final ReadWriteLock lock = new ReentrantReadWriteLock();

    public void readData() {
    
    
        lock.readLock().lock();
        try {
    
    
            // 读取共享资源的代码
        } finally {
    
    
            lock.readLock().unlock();
        }
    }

    public void writeData() {
    
    
        lock.writeLock().lock();
        try {
    
    
            // 写入共享资源的代码
        } finally {
    
    
            lock.writeLock().unlock();
        }
    }
}

上面的代码使用了Java中的ReentrantReadWriteLock类来实现读写锁。在读取共享资源时，使用读锁进行控制；在写入共享资源时，使用写锁进行控制。这样就可以避免读操作对写操作的饥饿，同时也避免写操作对读操作的饥饿。

需要注意的是，在使用读写锁时，要根据实际情况选择读锁和写锁的粒度。如果读操作和写操作的粒度太小，会导致读写锁的频繁切换，从而降低系统的性能；如果读操作和写操作的粒度太大，会导致读写锁的饥饿问题。因此，在使用读写锁时，需要根据具体的应用场景进行权衡和选择。

Simply put

Read-Write Locks: This mechanism allows multiple readers to access the shared resources concurrently, but only one writer can have exclusive access at a time. This can reduce write starvation while ensuring data consistency.
Fair Locks: Standard lock mechanisms often do not ensure fairness, which can lead to the situation where a thread has to wait indefinitely to acquire the lock. Fair locks ensure that threads waiting for the lock are granted access in the order in which they requested it, reducing starvation.
Lock Striping: This technique involves dividing the locks covering the resources into smaller sets, allowing multiple threads to access different sets of locks concurrently. This can reduce contention and mitigate starvation.
Queueing Locks: This approach involves creating a queue for threads waiting to acquire a lock. Threads are granted the lock in the order they arrived in the queue, avoiding starvation.
Optimistic Locking: This approach allows multiple threads to read a resource concurrently, but only one thread can modify it at a time. Other threads that try to modify the resource are informed of the conflict and required to retry the operation, avoiding write starvation.

说明

读写锁示例

Simply put

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