golang read-write lock implementation

Golang is a very popular modern programming language that supports high-concurrency and high-performance application development. In Golang, read-write lock is a common synchronization mechanism that allows multiple coroutines to read shared variables at the same time, but only allows one coroutine to write shared variables. In this article, we will introduce how to implement read-write lock using Golang.

Basic principle of read-write lock

Read-write lock is a synchronization mechanism that allows multiple coroutines to read shared variables at the same time, but only allows one coroutine to write shared variables. Read-write locks can effectively improve concurrency performance because it allows multiple coroutines to read shared variables at the same time, thereby reducing the number of contentions and lock contentions.

Read-write locks have two states: reading and writing. In the read state, multiple coroutines can read shared variables at the same time, while in the write state, only one coroutine is allowed to write shared variables. The state transition of read-write locks includes the following situations:

1. Read lock: Multiple coroutines can acquire read locks at the same time, but cannot acquire write locks.

2. Write lock: Only one coroutine can acquire the write lock, and other coroutines cannot acquire the read lock and write lock.

3. Unlocking: All coroutines can release read locks and write locks.

Now, let’s take a look at how to use Golang to implement read-write locks.

Code implementation

The Golang standard library has provided the implementation of read-write locks. We can directly use the RWMutex structure in the sync package to implement read-write locks.

First, let’s take a look at the definition of the RWMutex structure:

type RWMutex struct {

 //包含隐藏或非导出字段

}

RWMutex contains a hidden or non-exported field . It provides the following three methods:

1.RLock: Get the read lock

func (rw *RWMutex) RLock()

2.RUnlock: Release the read Lock

func (rw *RWMutex) RUnlock()

3.Lock: Get write lock

func (rw *RWMutex) Lock()

4.Unlock: Release the write lock

func (rw *RWMutex) Unlock()

Below we use a simple example to show how to use RWMutex to implement read and write locks:

package main

import (

"fmt"
"sync"

)

var (

count int
rw sync.RWMutex

)

func main() {

for i := 0; i < 10; i++ {
    go read(i)
}
for i := 0; i < 5; i++ {
    go write(i)
}
fmt.Scanln()

}

func read(n int) {

rw.RLock()
fmt.Println("读取协程", n, "开始读取数据")
v := count
fmt.Println("读取协程", n, "读取数据为:", v)
rw.RUnlock()

}

func write(n int) {

rw.Lock()
fmt.Println("写入协程", n, "开始写入数据")
count++
v := count
fmt.Println("写入协程", n, "写入数据为:", v)
rw.Unlock()

}

In the code, we define a shared variable count and a RWMutex object rw. We created 10 reading coroutines and 5 writing coroutines, and read and wrote shared variables in these coroutines.

In the read function, we use the RLock method to obtain the read lock, read the shared variable, and use the RUnlock method to release the read lock after the reading is completed. In the write function, we use the Lock method to acquire the write lock, write to the shared variable, and use the Unlock method to release the write lock after the writing is completed.

After running the code, you can see that multiple coroutines read and write shared variables concurrently, but only one coroutine can write to shared variables.

Summary

In this article, we introduced how to use Golang to implement read-write locks. We use the RWMutex structure in the sync package to implement read-write locks, and control the reading and writing of concurrent access shared variables through the RLock, RUnlock, Lock and Unlock methods. The implementation of read-write locks allows multiple coroutines to read shared variables concurrently, thereby improving performance and reducing the number of contentions and lock contentions.

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