What is deadlock in golang? How to avoid it?

1. What is deadlock?

In concurrent programming, when two or more processes (threads) wait for each other's resources to be released, a deadlock (Deadlock) will occur. To put it simply, each process occupies a part of the resources and needs to wait for the other party to release the resources to complete its own tasks, but the other party does the same. This will cause an endless loop of waiting, which will lead to the collapse of the entire system.

2. Golang implements deadlock

golang provides the sync package to support concurrent operations, of which Mutex is one of the common lock types in golang. Let's take Mutex as an example to demonstrate the implementation of golang deadlock.

Code example:

package main

import (
    "sync"
)

var mu sync.Mutex

func main() {
    mu.Lock()
    go func() {
        mu.Lock()
    }()
    mu.Unlock()
}

In this code, we create a variable mu of Mutex type. First, we call the Lock method of mu, obtain the mutex lock, and enter critical section. Next, we created a go process, in which we tried to obtain mu's Lock method again. Finally we release the mu mutex lock.

If we remove the mu.Unlock() statement in the above code, then the entire program will deadlock. Because in the go process, it will wait for the main process to release the lock before it can acquire the lock. However, the main process cannot continue to run because the lock is not released. In this way, the entire program will stay there and become a zombie process until the system is forcibly terminated.

3. How to avoid deadlock?

When multiple processes (threads) share the same resources, deadlock is prone to occur. So, how to avoid deadlock? You can refer to the following points:

1. Avoid multiple processes (threads) occupying the same resources at the same time;
2. When obtaining resources, obtain them in a certain order and do not cross resources;
3. Reduce the number and time of critical section resources as much as possible;
4. You can use channels in golang to avoid lock competition.

To sum up, deadlock is a common problem in concurrent programming and can easily occur in scenarios with fierce competition for resources. In order to avoid deadlocks, we need to abide by certain agreements, plan and use resources reasonably, obtain resources strictly in the order in which they are obtained, and use some mechanisms provided by golang to avoid lock competition.

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