二进制信号量和互斥量之间有区别吗?或者它们本质上是相同的?


当前回答

虽然二进制信号量可以用作互斥量,但互斥量是一个更具体的用例,因为只有锁定了互斥量的进程才应该解锁它。这种所有权限制使我们有可能对以下情况提供保护:

意外释放 递归死锁 任务死亡死锁

这些限制并不总是存在,因为它们降低了速度。在代码开发期间,您可以暂时启用这些检查。

例如,你可以在互斥锁中启用错误检查属性。错误检查互斥量返回EDEADLK,如果你试图锁定同一个互斥量两次,如果你解锁了一个不是你的互斥量,返回EPERM。

pthread_mutex_t mutex;
pthread_mutexattr_t attr;
pthread_mutexattr_init (&attr);
pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK_NP);
pthread_mutex_init (&mutex, &attr);

一旦初始化,我们可以将这些检查放在我们的代码中,就像这样:

if(pthread_mutex_unlock(&mutex)==EPERM)
 printf("Unlock failed:Mutex not owned by this thread\n");

其他回答

最好的解决方案

唯一的区别是

1.互斥锁-> lock和unlock属于锁定互斥锁的线程。

2.信号量->没有所有权,即;如果一个线程调用semwait(s),任何其他线程都可以调用sempost(s)来移除锁。

互斥量和二进制信号量是相同的用法,但实际上,它们是不同的。

对于互斥锁,只有锁定了它的线程才能解锁它。如果有其他线程来锁定它,它将等待。

对于信号电话来说,情况就不是这样了。信号量没有与特定的线程ID绑定。

互斥对象有所有权,不像信号量。尽管在互斥量范围内的任何线程都可以获得一个未锁定的互斥量,并锁定对同一关键代码段的访问,但只有锁定了互斥量的线程才应该解锁它。

互斥锁用于“锁定机制”。每次只有一个进程可以使用共享资源

信号量用于“信号机制” 比如“我完成了,现在可以继续了”

The basic issue is concurrency. There is more than one flow of control. Think about two processes using a shared memory. Now only one process can access the shared memory at a time. If more than one process accesses the shared memory at a time, the contents of shared memory would get corrupted. It is like a railroad track. Only one train can run on it, else there would be an accident.So there is a signalling mechanism, which a driver checks. If the signal is green, the train can go and if it is red it has to wait to use the track. Similarly in case of shared memory, there is a binary semaphore. If the semaphore is 1, a process acquires it (makes it 0) and goes ahead and accesses it. If the semaphore is 0, the process waits. The functionality the binary semaphore has to provide is mutual exclusion (or mutex, in short) so that only one of the many concurrent entities (process or thread) mutually excludes others. It is a plus that we have counting semaphores, which help in synchronizing multiple instances of a resource.

互斥是信号量提供的基本功能。现在在线程上下文中,我们可能有不同的名称和语法。但基本概念是相同的:如何在并发编程中保持代码和数据的完整性。在我看来,像所有权和相关检查这样的东西是由实现提供的改进。