Implementation of golang lock

The Golang language is a language that supports concurrent programming, which makes it very suitable for handling high-concurrency scenarios. In Golang, locks are one of the important tools to ensure data concurrency security. Locks can protect shared data and prevent data confusion caused by concurrent access. This article will introduce the implementation of Golang locks, including mutex locks, read-write locks and condition variables.

1. Mutex lock

Mutex lock is the most basic way to implement lock in Golang. The sync package is provided in Golang, and the sync.Mutex type is a mutex lock. Mutex locks provide two methods: Lock() and Unlock(). The Lock() method is used to acquire the lock. If the lock has been acquired by other goroutine, the goroutine will block waiting for the lock to be released; the Unlock() method is used to release the lock. If the lock has not been acquired, calling the Unlock() method will Causes a runtime panic. An example is as follows:

import "sync"

var lock sync.Mutex

func add(a, b int) int {
    lock.Lock()
    defer lock.Unlock() // 用defer关键字，确保即使函数意外返回也能正确释放锁
    return a + b
}

2. Read-write lock

The disadvantage of the mutex lock is that it is exclusive, that is, only one goroutine can acquire the lock at the same time, and other goroutines must wait. This is very wasteful for scenarios where there are many reads and few writes, because the read operations do not modify the shared data and should be able to be performed at the same time. To solve this problem, Golang provides read-write locks. Read-write locks have two states: read state and write state. In the read state, multiple goroutines can acquire read-write locks at the same time, and in the write state, only one goroutine can acquire the read-write lock. Read-write locks provide three methods: RLock(), RUnlock() and Lock(). The RLock() method is used to acquire the read lock. If one or more goroutines have acquired the read lock at this time, the new goroutine can directly acquire the read lock, otherwise it will block and wait for the read lock to be released; the RUnlock() method is used Release the read lock; the Lock() method is used to acquire the write lock. If a goroutine has acquired the read lock or write lock at this time, the new goroutine will block waiting for the lock to be released; the Unlock() method is used to release the write lock. Examples are as follows:

import "sync"

var rwLock sync.RWMutex

// 读操作获取读锁，写操作获取写锁
func get(name string) string {
    rwLock.RLock()
    defer rwLock.RUnlock()
    return m[name]
}

func set(name, value string) {
    rwLock.Lock()
    defer rwLock.Unlock()
    m[name] = value
}

3. Condition variable

Condition variable is an advanced synchronization primitive, which provides a mechanism that allows goroutine to wait for or notify an event to occur. Condition variables in Golang can be implemented through the Cond type in the sync package. The Cond type provides three methods: Wait(), Signal() and Broadcast(). The Wait() method is used to wait for notification in the waiting queue of the condition variable. When the notification is received, the Wait() method will automatically reacquire the lock; the Signal() method is used to send a notification to a goroutine in the waiting queue to be notified. The goroutine will return from the Wait() method; the Broadcast() method is used to send notifications to all goroutines in the waiting queue, and the notified goroutine will return from the Wait() method. An example is as follows:

import "sync"

var cond sync.Cond

// 生产者发送数据
func produce() {
    data := generateData()
    lock.Lock()
    buffer = append(buffer, data)
    lock.Unlock()

    // 发送通知
    cond.Signal()
}

// 消费者获取数据
func consume() {
    lock.Lock()
    // 如果缓冲区为空，则等待通知
    for len(buffer) == 0 {
        cond.Wait()
    }
    data := buffer[0]
    buffer = buffer[1:]
    lock.Unlock()

    processData(data)
}

Summary

By introducing the implementation of Golang locks in detail, we can understand that the locks provided in Golang are divided into three types: mutex locks, read-write locks and condition variables type. Mutex locks are suitable for exclusive access to shared data, read-write locks are suitable for reading more and writing less, and condition variables are suitable for waiting and notification scenarios. In actual development, we should choose appropriate locks according to specific scenarios to ensure the correctness and performance of concurrent operations.

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