An article explaining the lock mechanism in Go language in detail

As a highly concurrent programming language, the concurrency control mechanism of Go language is very important. One of the most commonly used mechanisms is the lock mechanism. This article will introduce how to implement the lock mechanism in Go language.

Go language lock

In the Go language, the most commonly used lock is the mutex lock (Mutex). A mutex is a special binary semaphore used to control access to shared resources. The Go language provides the mutex lock function through the "sync" package in the standard library. The type of mutex lock is defined as follows:

type Mutex struct {
    state int32
    sema  uint32
}

The state field is used to record the status of the lock, and the sema field is a semaphore.

Before using a mutex lock, you need to obtain the lock by calling the Lock method. If the lock is already held by another coroutine, the current coroutine will be blocked, waiting for the lock to be released. For example:

var mu sync.Mutex
// ...
mu.Lock()
// ...
mu.Unlock()

In this code, mu is a mutex lock. mu.Lock() is used to obtain the lock. If the lock is already held by other coroutines, the current coroutine will be blocked. mu.Unlock() is used to release the lock.

This mechanism is very simple, but in fact it is not very efficient. If there are many coroutines trying to acquire the same mutex, congestion will easily occur during processing, thus reducing the efficiency of the entire program.

Read-write lock

In some scenarios that require read and write operations, the efficiency of mutex locks is very low. Because the mutex lock can only guarantee that only one coroutine can access the shared resource at the same time, both read and write operations need to wait for the lock to be released first. However, if there are only read operations, this wait is not necessary. Because multiple coroutines can read the same resource at the same time without causing destructive modifications to the data.

At this time, you need to use the read-write lock (RWMutex). Read-write lock is a special kind of mutual exclusion lock. A resource can be read by multiple coroutines at the same time, but can only be written by one coroutine. Therefore, during a write operation, all read operations will be blocked, waiting for the write operation to complete. The types of read-write locks are defined as follows:

type RWMutex struct {
    w           Mutex // 用于写操作的互斥锁
    writerSem   uint32
    readerSem   uint32
    readerCount int32  // 当前进行读操作的协程数量
    readerWait  int32  // 等待读操作的协程数量
}

Read-write locks have two states: read lock and write lock. In the read lock state, multiple coroutines can perform read operations at the same time; in the write lock state, only one coroutine can perform write operations. At the same time, read-write locks support the coroutine priority mechanism, which means that coroutines that wait longer will acquire the lock first.

The method to obtain the read lock is RLock(), the method to release the read lock is RUnlock(); the method to obtain the write lock is Lock() , the method to release the write lock is Unlock(). For example:

var rw sync.RWMutex
// ...
func read() {
    rw.RLock()
    // ...
    rw.RUnlock()
}
// ...
func write() {
    rw.Lock()
    // ...
    rw.Unlock()
}

This code demonstrates how to use read-write locks in Go language. read() The function acquires the read lock and can be called by multiple coroutines at the same time; while the write() function acquires the write lock and can only have one coroutine at the same time. Call it.

sync.Once

sync.Once is a very useful lock. It only performs the initialization operation once. There is a Boolean value inside Once. If it is locked, once the call fails, subsequent calls will return immediately and the initialization will not be re-executed.

func singleton() {
    var once sync.Once
    once.Do(func() {
        // 初始化对象
    })
    // 使用对象
}

Using sync.Once can avoid repeated initialization operations in multiple coroutines.

Summary

In the Go language, the mechanism to implement multi-thread concurrency control is very important. By using mechanisms such as mutex locks, read-write locks, and Once, programs can become more efficient and safer when handling concurrent operations. In practice, various mechanisms need to be selected according to specific scenarios, and certain tests and verifications need to be conducted before selection and use.

The above is the detailed content of An article explaining the lock mechanism in Go language in detail. For more information, please follow other related articles on the PHP Chinese website!