The lock on the door is the toilet's mutex: it ensures that only one person can get inside. The lock on the partition door is like a mutex, and the line of people outside represents threads. The toilet is like an object that can be accessed by multiple threads. When a person enters a toilet partition, he locks the door from the inside. The term 'mutex' comes from 'MUTual EXclusion', which perfectly describes its purpose.ДЄs we said in one of our previous lessons, a mutex makes it possible to ensure that only one thread at a time has access to the object.ДЄ popular real-life example of a mutex involves toilets. Cat and Dog: all objects of all classes have a mutex. One is 'attached' to every object in Java - you already know that :) It doesn't matter if you use standard classes or create your own classes, e.g. MutexA mutex (or lock) is a special mechanism for synchronizing threads. We'll look at a few examples and come to a definitive understanding of how these concepts differ from one another :) That's why we're going to investigate these three terms. It also has a very similar function to monitors and mutexes. Additionally, when you read lessons and watch videos about multithreading on other websites, you'll come across another similar concept: 'semaphore'. 'Mutex' and 'monitor' are actually related concepts. If yes, well done! If not (this is most common), that's no surprise. Without peeking, can you say how they differ? :) Pshared is non-zero, but the system does not yet support process sharing semaphores.Hi! When you studied multithreading on CodeGym, you frequently encountered the concepts of 'mutex' and 'monitor'. Sem_init() returns when successful 0 On error, return- 1, And set errno to an appropriate value. Value: Specify the size of the semaphore value When it is not 0, this semaphore is shared among processes, otherwise it can only be shared by all threads of the current process. Pshared: Specifies the type of semaphore. The result of initializing an already initialized semaphore is undefined. All processes that can access the shared memory area can use sem_post( 3)гЂЃsem_wait( 3 ) And so on to manipulate semaphores. The created child inherits the memory map of its father, so it can also see this semaphore. If pshared is non-zero, then the semaphore will be shared between processes and the shared memory area should be located (see shm_open( 3)гЂЃmmap( 2) And shmget( 2)). Int sem_init(sem_t *sem, int pshared, unsigned int value) If pshared is 0, then the initialized semaphore is shared among the threads of the same process. The well-known semaphore can be used for inter-thread synchronization as well as inter-process synchronization.

Sem_open: Create a new well-known semaphore or open an existing well-known semaphore. The memory semaphore (unnamed semaphore) is shown below:

Ps: The reason for providing the semaphore is that in the case of inter-process synchronization, if the shared memory area is not involved, the semaphore needs to be used.ДЎ, posix provides semaphores in quantities: well-known semaphores and memory-based semaphores, the latter is called unnamed semaphores. However, when sending a signal to a condition variable, if no thread is waiting on the condition variable, the signal will be lost. Since the semaphore has a state (its value) associated with it, the hang-out operation of the semaphore is always remembered.

The mutex is either locked or unlocked (binary state, similar to binary semaphore)ДЈ.

The mutex must always be unlocked by the thread that locks it, and the hanging of the semaphore does not have to be executed by the same thread that has performed its waiting operation.Дў.

Duffrence between semaphor and mutex