How does a mutex lock work?

How does a mutex lock work?

Mutex lock will only be released by the thread who locked it. So this ensures that once a thread has locked a piece of code then no other thread can execute the same region until it is unlocked by the thread who locked it.

What happens when mutex is locked?

Mutexes are used to protect shared resources. If the mutex is already locked by another thread, the thread waits for the mutex to become available. The thread that has locked a mutex becomes its current owner and remains the owner until the same thread has unlocked it.

How do you make a mutex lock?

What you need to do is to call pthread_mutex_lock to secure a mutex, like this: pthread_mutex_lock(&mutex); Once you do this, any other calls to pthread_mutex_lock(mutex) will not return until you call pthread_mutex_unlock in this thread.

What is mutex lock in OS?

Strictly speaking, a mutex is a locking mechanism used to synchronize access to a resource. Only one task (can be a thread or process based on OS abstraction) can acquire the mutex. It means there is ownership associated with a mutex, and only the owner can release the lock (mutex).

Can pthread_mutex_lock fail?

The mutex was created with the protocol attribute having the value PTHREAD_PRIO_PROTECT and the calling thread’s priority is higher than the mutex’s current priority ceiling. The pthread_mutex_lock() function may fail if: [EDEADLK] A deadlock condition was detected or the current thread already owns the mutex.

When should you use a mutex lock?

Mutex: Use a mutex when you (thread) want to execute code that should not be executed by any other thread at the same time. Mutex ‘down’ happens in one thread and mutex ‘up’ must happen in the same thread later on.

Can we use mutex between processes?

Mutexes can synchronize threads within the same process or in other processes. Mutexes can be used to synchronize threads between processes if the mutexes are allocated in writable memory and shared among the cooperating processes (see mmap(2)), and have been initialized for this task.

Why is mutex expensive?

Mutex can be considered as an integer in memory. A thread trying to lock on a mutex has to read the existing state of the mutex and can set it depending on the value read. The overall costs of using a mutex sums up to the test-and-set operation and the system calls used to implement the mutex.

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