在 Go 中保護(hù)臨界區(qū)的標(biāo)準(zhǔn)方法是使用 sync.Mutex 的 Lock() 和 Unlock() 方法。1. 聲明一個(gè) mutex 并將其與要保護(hù)的數(shù)據(jù)一起使用；2. 在進(jìn)入臨界區(qū)前調(diào)用 Lock()，確保只有一個(gè) goroutine 能訪問共享資源；3. 使用 defer Unlock() 確保鎖始終被釋放，避免死鎖；4. 盡量縮短臨界區(qū)內(nèi)的操作以提高性能；5. 對(duì)于讀多寫少的場(chǎng)景，應(yīng)使用 sync.RWMutex，通過 RLock()/RUnlock() 進(jìn)行讀操作，通過 Lock()/Unlock() 進(jìn)行寫操作，從而提升并發(fā)效率。

When you need to protect a critical section of code in Go, using the Lock() and Unlock() methods from the sync.Mutex type is the standard approach. These methods help ensure that only one goroutine can access the protected section at any given time, preventing race conditions.

What is a Mutex in Go?

Go's sync.Mutex is a mutual exclusion lock used to synchronize access to shared resources across multiple goroutines. When a goroutine calls Lock(), it blocks until the mutex becomes available if it's already locked by another goroutine. Once done with the critical section, calling Unlock() releases the lock so others can proceed.

Here’s how to declare and use a mutex:

var mu sync.Mutex

You typically embed this mutex alongside the data it protects. It's common to see this pattern when working with structs or global variables shared between goroutines.

How to Use Lock() and Unlock() Correctly

The most important thing is to always call Unlock() after finishing work in the critical section — even if an error occurs. A common practice is to use defer mu.Unlock() right after calling mu.Lock().

Here’s a basic example:

package main

import (
    "fmt"
    "sync"
)

var (
    counter = 0
    mu      sync.Mutex
)

func increment(wg *sync.WaitGroup) {
    defer wg.Done()
    mu.Lock()
    defer mu.Unlock()
    counter  
}

func main() {
    var wg sync.WaitGroup
    for i := 0; i < 1000; i   {
        wg.Add(1)
        go increment(&wg)
    }
    wg.Wait()
    fmt.Println("Final counter:", counter)
}

In this example:

• Multiple goroutines try to increment a shared counter.
• The mu.Lock() ensures only one goroutine can enter the critical section at a time.
• defer mu.Unlock() guarantees the lock is released even if something goes wrong inside the block.

Some key points:

• Always pair Lock() and Unlock() together.
• Prefer deferring Unlock() immediately after locking.
• Avoid long-running operations inside a locked section — keep critical sections as short as possible.

Common Mistakes to Avoid

Even experienced developers sometimes make mistakes when managing locks. Here are a few pitfalls to watch out for:

• Forgetting to unlock: This leads to deadlocks. If one goroutine locks but never unlocks, other goroutines waiting on the same lock will be stuck forever.
• Double locking the same mutex: Calling Lock() again on the same mutex without unlocking first causes a deadlock.
• Copying a locked mutex: Go discourages copying values of types that contain mutexes. Doing so can break the synchronization logic silently.

To prevent these issues:

• Use defer mu.Unlock() whenever possible.
• Be careful when passing structs containing mutexes — pass by pointer instead of by value.
• Consider using tools like -race flag (go run -race) to detect race conditions during testing.

When to Use RWMutex Instead

If your application has more read operations than writes, consider using sync.RWMutex. It allows multiple readers but gives exclusive access to a single writer.

• Use RLock() / RUnlock() for reading.
• Use Lock() / Unlock() when writing.

This can significantly improve performance in read-heavy scenarios. But remember: a write lock blocks all reads, and a read lock blocks writes.

So in cases where:

• You have many concurrent readers,
• Writes are infrequent,

...using RWMutex might be a better fit than a regular Mutex.

基本上就這些。

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