# spin_rw_mutex

[mutex.spin_rw_mutex]

A `spin_rw_mutex` is a class that models the ReaderWriterMutex requirement and satisfies all requirements of shared mutex type from the [thread.sharedmutex.requirements] ISO C++ section.

The `spin_rw_mutex` class is unfair spinning reader-writer lock with backoff and writer-preference.

    // Defined in header <oneapi/tbb/spin_rw_mutex.h>

    namespace oneapi {
    namespace tbb {
        class spin_rw_mutex {
        public:
            spin_rw_mutex() noexcept;
            ~spin_rw_mutex();

            spin_rw_mutex(const spin_rw_mutex&) = delete;
            spin_rw_mutex& operator=(const spin_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;
        };
    } // namespace tbb
    } // namespace oneapi

## Member classes

class scoped_lock

  Corresponding scoped-lock class. See the ReaderWriterMutex requirement.

## Member functions

spin_rw_mutex()

  Constructs unlocked `spin_rw_mutex`.

~spin_rw_mutex()

  Destroys unlocked `spin_rw_mutex`.

void lock()

  Acquires a lock. Spins if the lock is taken.

bool try_lock()

  Attempts to acquire a lock (non-blocking) on write. Returns true if the lock is acquired on write; false otherwise.

void unlock()

  Releases a write lock, held by the current thread.

void lock_shared()

  Acquires a lock on read. Spins if the lock is taken on write already.

bool try_lock_shared()

  Attempts to acquire the lock (non-blocking) on read. Returns true if the lock is acquired on read; false, otherwise.

void unlock_shared()

  Releases a read lock held by the current thread.