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class SF::Mutex
inherits Reference #

Blocks concurrent access to shared resources from multiple threads

Mutex stands for "MUTual EXclusion". A mutex is a synchronization object, used when multiple threads are involved.

When you want to protect a part of the code from being accessed simultaneously by multiple threads, you typically use a mutex. When a thread is locked by a mutex, any other thread trying to lock it will be blocked until the mutex is released by the thread that locked it. This way, you can allow only one thread at a time to access a critical region of your code.

Usage example:

@database = Database.new # this is a critical resource that needs some protection
@mutex = SF::Mutex.new

def thread1()
  @mutex.lock() # this call will block the thread if the mutex is already locked by thread2
  @database.write(...)
  @mutex.unlock() # if thread2 was waiting, it will now be unblocked
end

def thread2()
  @mutex.lock() # this call will block the thread if the mutex is already locked by thread1
  @database.write(...)
  @mutex.unlock() # if thread1 was waiting, it will now be unblocked
end

Be very careful with mutexes. A bad usage can lead to bad problems, like deadlocks (two threads are waiting for each other and the application is globally stuck).

To make the usage of mutexes more robust, particularly in environments where exceptions can be thrown, you should use the helper method synchronize to lock/unlock mutexes.

SFML mutexes are recursive, which means that you can lock a mutex multiple times in the same thread without creating a deadlock. In this case, the first call to lock() behaves as usual, and the following ones have no effect. However, you must call unlock() exactly as many times as you called lock(). If you don't, the mutex won't be released. However, you must call unlock() exactly as many times as you called lock(). If you don't, the mutex won't be released.

See also: SF::Lock

Included modules

SF::NonCopyable

Class methods#

.new #

Default constructor

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Methods#

#finalize #

Destructor

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#lock #

Lock the mutex

If the mutex is already locked in another thread, this call will block the execution until the mutex is released.

See also: unlock

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#synchronize #

Lock the mutex, execute the block, then unlock the mutex (even if an exception is raised).

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#unlock #

Unlock the mutex

See also: lock

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