.. _rw_mutex:
rw_mutex
=============
.. note::
To enable this feature, define the ``TBB_PREVIEW_MUTEXES`` macro to 1.
Description
***********
A ``rw_mutex`` is a class that models the `ReaderWriterMutex requirement <https://spec.oneapi.com/versions/latest/elements/oneTBB/source/named_requirements/mutexes/rw_mutex.html>`_,
using adaptive approach: the combination of spinlock and waiting on system primitives.
The ``rw_mutex`` class satisfies all of the shared mutex requirements described in the [thread.sharedmutex.requirements] section of the ISO C++ standard.
The ``rw_mutex`` class is unfair reader-writer lock with writer-preference.
API
***
Header
------
.. code:: cpp
#include <oneapi/tbb/rw_mutex.h>
Synopsis
--------
.. code:: cpp
namespace oneapi {
namespace tbb {
class rw_mutex {
public:
rw_mutex() noexcept;
~rw_mutex();
rw_mutex(const rw_mutex&) = delete;
rw_mutex& operator=(const rw_mutex&) = delete;
class scoped_lock;
// exclusive ownership
void lock();
bool try_lock();
void unlock();
// shared ownership
void lock_shared();
bool try_lock_shared();
void unlock_shared();
static constexpr bool is_rw_mutex = true;
static constexpr bool is_recursive_mutex = false;
static constexpr bool is_fair_mutex = false;
};
}
}
Member classes
--------------
.. namespace:: tbb::rw_mutex
.. cpp:class:: scoped_lock
The corresponding scoped-lock class. See the `ReaderWriterMutex requirement <https://spec.oneapi.com/versions/latest/elements/oneTBB/source/named_requirements/mutexes/rw_mutex.html>`_.
Member functions
----------------
.. cpp:function:: rw_mutex()
Constructs unlocked ``rw_mutex``.
--------------------------------------------------
.. cpp:function:: ~rw_mutex()
Destroys unlocked ``rw_mutex``.
--------------------------------------------------
.. cpp:function:: void lock()
Acquires a lock. It uses adaptive logic for waiting: it blocks after particular time period of busy wait.
--------------------------------------------------
.. cpp:function:: bool try_lock()
Tries to acquire a lock (non-blocking) on write. Returns **true** if succeeded; **false** otherwise.
--------------------------------------------------
.. cpp:function:: void unlock()
Releases the write lock held by the current thread.
--------------------------------------------------
.. cpp:function:: void lock_shared()
Acquires a lock on read. It uses adaptive logic for waiting: it blocks after particular time period of busy wait.
--------------------------------------------------
.. cpp:function:: bool try_lock_shared()
Tries to acquire the lock (non-blocking) on read. Returns **true** if succeeded; **false** otherwise.
--------------------------------------------------
.. cpp:function:: void unlock_shared()
Releases the read lock held by the current thread.
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