The art of solving deadlocks with golang functions

Golang provides the following functions to solve the deadlock problem: sync.Mutex: Mutex lock, ensuring that only one thread can access protected resources at the same time. sync.RWMutex: Read-write lock, which allows multiple threads to read resources at the same time, but only allows one thread to write resources.

Golang Function: The Art of Solving Deadlock

Deadlock is often encountered in concurrent programming, that is, two or more processes or threads They compete with each other for resources, causing the program to reach a deadlock. Golang provides some functions to help solve deadlock problems, and this article will introduce the most commonly used functions.

sync.Mutex

sync.Mutex is a mutex lock, which ensures that only one thread can access protected resources at the same time. The syntax for using sync.Mutex is as follows:

import "sync"

var mu sync.Mutex

func main() {
    mu.Lock()
    // 访问受保护的资源
    mu.Unlock()
}

In the above example, the Lock() method blocks the thread until the lock is unlocked. Unlock() The method releases the lock, allowing other threads to access the protected resource.

sync.RWMutex

sync.RWMutex is a read-write lock that allows multiple threads to read resources at the same time, but only allows one thread to write to resources. The syntax for using sync.RWMutex is as follows:

import "sync"

var rwmu sync.RWMutex

func main() {
    rwmu.RLock()
    // 读取受保护的资源
    rwmu.RUnlock()

    rwmu.Lock()
    // 写入受保护的资源
    rwmu.Unlock()
}

In the above example, the RLock() method allows multiple threads to read resources simultaneously, while The Lock() method blocks the thread until the lock is unlocked.

Deadlock Example

The following is an example of a deadlock:

import "sync"

var mu1 sync.Mutex
var mu2 sync.Mutex

func f1() {
    mu1.Lock()
    mu2.Lock()
    // ...
}

func f2() {
    mu2.Lock()
    mu1.Lock()
    // ...
}

In this example, the functions f1() and f2( ) will try to compete for two mutex locks, eventually leading to deadlock.

Prevent deadlock

To prevent deadlock, you can use the following tips:

• Avoid two threads trying to compete for the lock in the opposite order.
• Only contend for necessary locks.
• Use a timer or timeout mechanism to detect and break deadlocks.
• Use sync.Once to ensure that the code is executed only once.

Practical case

In a concurrent web application, we can use sync.Mutex to protect access to the database:

import (
    "database/sql"
    "sync"
)

var db *sql.DB
var dbLock sync.Mutex

func init() {
    db, _ = sql.Open("mysql", "root:password@localhost:3306/test")
}

func GetUserData(userID int) (*User, error) {
    dbLock.Lock()
    defer dbLock.Unlock()

    // 从数据库中查询用户数据
}

By using sync.Mutex, we can ensure that only one thread can access the database connection at the same time, thus avoiding problems such as data inconsistency that may occur when accessing the database concurrently.

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