In-depth analysis of the underlying implementation mechanism of Golang locks

Detailed explanation of the underlying implementation principles of Golang locks, specific code examples are required

Overview:
Concurrent programming is a very important part of modern software development, and locks are A mechanism to implement concurrency control. In Golang, the concept of locks is widely used in concurrent programming. This article will deeply explore the underlying implementation principles of Golang locks and provide specific code examples.

1. The underlying implementation principle of mutex lock (Mutex)
   Mutex lock is one of the most commonly used lock types in Golang. It uses an underlying data structure sync.Mutex to implement.

The definition of Mutex is as follows:

type Mutex struct {

state int32
sema  uint32

}

Among them, state represents the status of the mutex lock, sema represents a semaphore, used to coordinate multiple coroutines to achieve mutual exclusion.

The code for using mutex locks to limit critical sections is as follows:

var counter int
var mutex sync.Mutex

func increment() {

mutex.Lock()
counter++
mutex.Unlock()

}

In the above code, the mutex lock mutex is used to limit the critical section of the counter, ensuring that the operation of the counter will not be affected by concurrency.

The underlying implementation principle of the mutex lock is based on the atomic operation and semaphore mechanism in the operating system. When a coroutine calls mutex.Lock(), it will try to obtain the status of the mutex lock. If the mutex lock is currently unlocked, the coroutine will set its status to locked and continue execution; otherwise, the mutex lock will be unlocked. The coroutine will be placed in the waiting queue, waiting for other coroutines to release the lock.

When a coroutine calls mutex.Unlock(), it releases the mutex lock status and wakes up a coroutine in the waiting queue. The awakened coroutine can try to obtain the status of the mutex again and continue execution.

2. The underlying implementation principle of read-write lock (RWMutex)
   In addition to mutex locks, Golang also provides a read-write lock (RWMutex) type to implement reading between multiple coroutines. Concurrency control for writing data.

The definition of RWMutex is as follows:

type RWMutex struct {

// 互斥锁，用于保护读写锁的读写操作
w Mutex

// 唤醒等待队列的信号量
writerSem uint32
readerSem uint32

// 等待的读协程数量
readerCount int32

// 等待的写协程数量
readerWait int32
writerWait int32

}

Code that uses read-write locks for critical section restrictions As shown below:

var counter int
var rwMutex sync.RWMutex

func read() {

rwMutex.RLock()
defer rwMutex.RUnlock()
// 读取counter的操作

}

func write() {

rwMutex.Lock()
defer rwMutex.Unlock()
// 更新counter的操作

}

The underlying implementation principle of the read-write lock is to add a read-write waiting queue based on the mutex lock. When a coroutine calls rwMutex.RLock(), it attempts to acquire a read lock. If no other coroutine holds the write lock, the current coroutine can successfully acquire the read lock and continue execution; otherwise, the coroutine will be placed in the read waiting queue.

When a coroutine calls rwMutex.RUnlock(), it releases the read lock and wakes up other coroutines in the waiting queue. The awakened coroutine can try to acquire the read lock again.

Similarly, when a coroutine calls rwMutex.Lock(), it will try to acquire the write lock. If no other coroutine holds a read lock or a write lock, the current coroutine can successfully acquire the write lock and continue execution; otherwise, the coroutine will be placed in the write waiting queue.

When a coroutine calls rwMutex.Unlock(), it releases the write lock and wakes up other coroutines in the waiting queue. The awakened coroutine can try to acquire the read or write lock again.

Summary:
This article introduces the underlying implementation principles of Golang locks in detail, and provides specific code examples of mutex locks and read-write locks. The mutex lock uses the underlying semaphore mechanism to realize mutual exclusion control of the critical section, while the read-write lock adds a read-write waiting queue on the basis of the mutex lock to realize the control of read and write operations between multiple coroutines. Concurrency control. A deep understanding of the underlying implementation principles of Golang locks is very important for writing efficient and correct concurrent programs.

The above is the detailed content of In-depth analysis of the underlying implementation mechanism of Golang locks. For more information, please follow other related articles on the PHP Chinese website!