.. role:: blue
   :class: blue

Synchronization Objects
=======================
.. _Synchronization_objects_:

.. версия ядра: 

The synchronization objects are defined in the *tool_mutex.h* file.

Locks
-----

By default the kernel uses lock classes implemented on the basis of system synchronization API that enables safe use of alternative parallel frameworks (not only OpenMP) in user applications.

But the kernel can be switched to using locks based on OpenMP locks.

On Windows system locks by default are implemented on the basis of critical sections. On Linux system locks are implemented on the basis of pthread_mutex_t.

The lock classes implementation is controlled by the **C3D_NATIVE_LOCK** variable. Redefining the **C3D_NATIVE_LOCK** variable in user applications is prohibited.

The **CommonMutex** and **CommonRecursiveMutex** classes define lock and recursive lock. They provide the :blue:`lock`\() and :blue:`unlock`\() methods.

The **ScopedLock** and **ScopedRecursiveLock** classes define scoped lock and scoped recursive lock. They can accept a null pointer to a mutex. Locking occurs if the pointer to the mutex is nonzero and the code runs in parallel.

Base Synchronization Objects
----------------------------

The **MbSyncItem** class is the base synchronization object with lazy initialization. It creates a lock (mutex) when needed and implements the **Lock()** and **Unlock()** methods.

The **MbNestSyncItem** class is the base synchronization object with lazy initialization which supports nested locks. It creates a lock (mutex) when needed and implements the **Lock()** and **Unlock()** methods.

The **MbPersistentSyncItem** class is the base synchronization object implementing the **Lock()** and **Unlock()** methods. It always creates a lock (mutex).

The **MbPersistentNestSyncItem** class is the base synchronization object which supports nested locks. It implements the **Lock()** and **Unlock()** methods and always creates a lock (mutex).

The kernel objects that need synchronization are inherited from one of these classes.