Where does golang need to lock?

In golang programming, locks are an important mechanism for controlling concurrency. However, locking is not required in all cases. In some cases, locking will increase the complexity of the code and affect performance.

So, under what circumstances do locks need to be locked in golang programming?

1. Multiple goroutines access shared variables

When multiple goroutines write to the same variable at the same time, they need to be locked. This is because synchronization in golang is accomplished through channels and lock mechanisms. If the lock is not locked, a race condition may occur, resulting in data inconsistency.

For example:

var count int
func addCount(value int) {
   count += value
}

In this example, if multiple goroutines call the addCount function at the same time, the value of count will be incorrect.

In order to solve this problem, you can use the sync.Mutex type to lock, for example:

var count int
var mu sync.Mutex
func addCount(value int) {
   mu.Lock()
   defer mu.Unlock()
   count += value
}

In this example, use mu.Lock() To lock count to ensure that each goroutine can exclusively occupy the variable when operating.

2. Multiple goroutines perform read and write operations

When multiple goroutines perform read and write operations, locking is also required. This is because in golang, reading and writing are both atomic operations, but there may be overlap between read and write operations, resulting in data inconsistency.

For example:

var m map[int]string
func writeToMap(key int, value string) {
   m[key] = value
}
func readFromMap(key int) string {
   return m[key]
}

In this example, if multiple goroutines perform read and write operations on map at the same time, it will cause a race condition, resulting in data of inconsistency.

In order to solve this problem, you can use the sync.RWMutex type to lock, for example:

var m map[int]string
var mu sync.RWMutex
func writeToMap(key int, value string) {
   mu.Lock()
   defer mu.Unlock()
   m[key] = value
}
func readFromMap(key int) string {
   mu.RLock()
   defer mu.RUnlock()
   return m[key]
}

In this example, use mu.RLock() and mu.RUnlock() lock and unlock reading and writing respectively.

3. Synchronization between multiple goroutines

When synchronization is required between multiple goroutines, locking is also required. Channels are often used in golang to synchronize between goroutines, but when channels are not applicable, a lock mechanism needs to be used.

For example:

var wg sync.WaitGroup
var mu sync.Mutex
var data []int
func worker() {
   defer wg.Done()
   for i := 0; i < 1000; i++ {
      mu.Lock()
      data = append(data, i)
      mu.Unlock()
   }
}
func main() {
   for i := 0; i < 10; i++ {
      wg.Add(1)
      go worker()
   }
   wg.Wait()
   fmt.Println(data)

In this example, 10 goroutines add 1000 integers to data at the same time. Since data is a shared variable, you need to use sync.Mutex to lock it.

To sum up, in golang programming, situations where locks need to be used include situations where multiple goroutines access shared variables, multiple goroutines perform read and write operations, and situations where synchronization is required between multiple goroutines. When using locks, you need to choose the appropriate lock type according to the actual situation to ensure the correctness and performance of the program.

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