std::recursive_mutex
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                    |   Defined in header  <mutex>
  | 
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|   class recursive_mutex;  | 
(since C++11) | |
The recursive_mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads.
recursive_mutex offers exclusive, recursive ownership semantics:
-  A calling thread owns a 
recursive_mutexfor a period of time that starts when it successfully calls eitherlockortry_lock. During this period, the thread may make additional calls tolockortry_lock. The period of ownership ends when the thread makes a matching number of calls tounlock. -  When a thread owns a 
recursive_mutex, all other threads will block (for calls tolock) or receive a false return value (fortry_lock) if they attempt to claim ownership of therecursive_mutex. -  The maximum number of times that a 
recursive_mutexmay be locked is unspecified, but after that number is reached, calls tolockwill throw std::system_error and calls totry_lockwill return false. 
The behavior of a program is undefined if a recursive_mutex is destroyed while still owned by some thread.  The recursive_mutex class satisfies all requirements of Mutex and StandardLayoutType.
Member types
| Member type | Definition | 
  native_handle_type(optional)
 | 
implementation-defined | 
Member functions
|   constructs the mutex  (public member function)  | |
|   destroys the mutex  (public member function)  | |
|    operator= [deleted]  | 
   not copy-assignable  (public member function)  | 
 Locking | |
|    locks the mutex, blocks if the mutex is not available  (public member function)  | |
|    tries to lock the mutex, returns if the mutex is not available  (public member function)  | |
|    unlocks the mutex  (public member function)  | |
 Native handle | |
|    returns the underlying implementation-defined native handle object  (public member function)  | |