
【计】 queueing semaphore
排队信号量(Queuing Semaphore)是操作系统和并发编程中的一种同步机制,主要用于管理多线程/进程对共享资源的有序访问。其核心特点是通过内置的等待队列实现线程的排队机制,确保资源分配的公平性。以下是详细解释:
信号量本质
信号量是一个计数器,通过P()
(等待/获取)和V()
(释放)操作控制资源访问。
排队机制的作用
传统信号量可能因无序竞争导致“线程饥饿”(某些线程长期无法获取资源)。排队信号量通过维护先到先得(FIFO)的等待队列,确保线程按请求顺序获取资源,解决公平性问题。
有序唤醒
当资源释放(V()
操作)时,优先唤醒队列中等待最久的线程,而非随机唤醒。
避免优先级反转
在高优先级线程频繁请求的场景下,排队机制可防止低优先级线程因抢占问题被长期阻塞。
实现公平性
典型应用如数据库连接池、打印机调度等需严格按请求顺序分配资源的场景。
特性 | 普通信号量 | 排队信号量 |
---|---|---|
唤醒策略 | 随机或依赖系统调度 | 严格按队列顺序唤醒 |
公平性 | 可能导致饥饿 | 保证先请求者先获取 |
实现复杂度 | 简单 | 需额外维护等待队列 |
信号量操作可抽象为:
$$
text{初始化:} S = N quad (N为初始资源数)
$$
$$
P(): text{while } S leq 0 text{ wait}; quad S = S - 1
$$
$$
V(): S = S + 1; text{唤醒队首线程}
$$
如果需要更具体的编程实现(如Java的Semaphore
公平模式),可补充说明或提供代码示例。
排队信号量(pái duì xìn hào liàng)是一种同步工具,常用于多个进程或线程之间的协作。
The English translation for 排队信号量 is semaphore. It is a synchronization tool commonly used for coordination between multiple processes or threads.
The pronunciation of semaphore is /ˈsɛməfɔːr/.
In computer science, semaphore is often used as a way for multiple processes to access a shared resource or protect critical sections of code. It is typically used in operating systems, database management systems, and other systems where multiple processes may need to access a shared resource simultaneously.
Some synonyms for semaphore include mutex, lock, and monitor. These terms are also used for synchronization and coordination between multiple processes in computer science.
There is no direct antonym for semaphore in computer science, but it can be contrasted with asynchronous communication, which does not rely on synchronization between processes.
Semaphore is a common term in computer science and is widely used in programming and software development. It is not commonly used in everyday conversation, but it is well-known among computer scientists and other technology professionals.
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