Process management and thread synchronization in C++

C is a very popular programming language, especially widely used in system programming and embedded development. In C, process management and thread synchronization are very important concepts. Process management refers to how the operating system manages processes, while thread synchronization refers to how multiple threads coordinate and cooperate to achieve common tasks. This article will introduce the basic principles and common methods of process management and thread synchronization in C.

1. Process Management

A process refers to an instance of a program being executed. It has its own memory space, CPU time, files, network and other resources. The operating system allocates certain resources to each process and manages them according to certain rules. In C, processes can be managed through the process management functions provided by the operating system. Common functions are as follows:

1. fork() function: Create a new process and copy a copy of the child process to the child process. . The main difference of a subprocess is that it has independent registers, stack, virtual memory space and file descriptors, but they share the same program and data segments. The parent process and child process can determine whether they are on different code paths through the return value.
2. exec() function: used to replace the address space of the current process to run a new program. After executing exec, the code segment, data segment and stack of the original process are replaced with the contents of the new program. Therefore, dynamic loading of programs can be achieved using the exec() function.
3. wait() function: wait for a child process to complete. If the child process has ended, the wait function will return the exit code of the child process. If the child process has not ended, the wait function will block the current process until the child process ends.
4. exit() function: Terminate the current process and return an exit code. If a process calls the exit() function, its resources will be released, including open files, allocated memory, and runtime data.

2. Thread synchronization

Thread synchronization refers to how multiple threads coordinate and cooperate to achieve common tasks. In C, thread synchronization is usually implemented through locks, which can be implemented in a variety of ways, such as mutex locks, read-write locks, condition variables, etc. Here are several common thread synchronization methods:

1. Mutex lock: Mutex lock is the most basic thread synchronization method, which ensures that only one thread can operate shared resources at the same time. After a thread enters the critical section protected by a mutex lock, the lock will be set to "occupied". When other threads need to access the same shared resource, they must wait for the lock to be released before they can access it. Mutex locks can be implemented through functions such as pthread_mutex_init(), pthread_mutex_lock(), and pthread_mutex_unlock() in the Pthread library.
2. Read-write lock: Read-write locks are divided into two types: read locks and write locks. Read locks can be held by multiple threads at the same time, but write locks must only be held by one thread. In the read lock state, other threads cannot enter the write lock state; in the write lock state, other threads cannot enter the read lock or write lock state. Read-write locks can be implemented through functions such as pthread_rwlock_init(), pthread_rwlock_rdlock(), pthread_rwlock_wrlock(), and pthread_rwlock_unlock() in the Pthread library.
3. Condition variable: Condition variable is a thread synchronization mechanism that allows the calling thread to block until a certain condition is met. When the condition is not met, the waiting thread will be blocked; when the condition is met, the waiting thread will be awakened. Condition variables can be implemented through functions such as pthread_cond_init(), pthread_cond_wait(), pthread_cond_signal(), and pthread_cond_broadcast() in the Pthread library.

The above are some common process management and thread synchronization methods. In C development, process management and thread synchronization have always been the focus of developers' attention. Understanding the basic principles and usage of these methods can help developers complete their programming work better and improve the maintainability and reliability of the code.

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