reader_writer_lock Class
A writer-preference queue-based reader-writer lock with local only spinning. The lock grants first in - first out (FIFO) access to writers and starves readers under a continuous load of writers.
Syntax
class reader_writer_lock;
Members
Public Classes
| Name | Description |
|---|---|
| reader_writer_lock::scoped_lock Class | An exception safe RAII wrapper that can be used to acquire reader_writer_lock lock objects as a writer. |
| reader_writer_lock::scoped_lock_read Class | An exception safe RAII wrapper that can be used to acquire reader_writer_lock lock objects as a reader. |
Public Constructors
| Name | Description |
|---|---|
| reader_writer_lock | Constructs a new reader_writer_lock object. |
| ~reader_writer_lock Destructor | Destroys the reader_writer_lock object. |
Public Methods
| Name | Description |
|---|---|
| lock | Acquires the reader-writer lock as a writer. |
| lock_read | Acquires the reader-writer lock as a reader. If there are writers, active readers have to wait until they are done. The reader simply registers an interest in the lock and waits for writers to release it. |
| try_lock | Attempts to acquire the reader-writer lock as a writer without blocking. |
| try_lock_read | Attempts to acquire the reader-writer lock as a reader without blocking. |
| unlock | Unlocks the reader-writer lock based on who locked it, reader or writer. |
Remarks
For more information, see Synchronization Data Structures.
Inheritance Hierarchy
reader_writer_lock
Requirements
Header: concrt.h
Namespace: concurrency
lock
Acquires the reader-writer lock as a writer.
void lock();
Remarks
It is often safer to utilize the scoped_lock construct to acquire and release a reader_writer_lock object as a writer in an exception safe way.
After a writer attempts to acquire the lock, any future readers will block until the writers have successfully acquired and released the lock. This lock is biased towards writers and can starve readers under a continuous load of writers.
Writers are chained so that a writer exiting the lock releases the next writer in line.
If the lock is already held by the calling context, an improper_lock exception will be thrown.
lock_read
Acquires the reader-writer lock as a reader. If there are writers, active readers have to wait until they are done. The reader simply registers an interest in the lock and waits for writers to release it.
void lock_read();
Remarks
It is often safer to utilize the scoped_lock_read construct to acquire and release a reader_writer_lock object as a reader in an exception safe way.
If there are writers waiting on the lock, the reader will wait until all writers in line have acquired and released the lock. This lock is biased towards writers and can starve readers under a continuous load of writers.
reader_writer_lock
Constructs a new reader_writer_lock object.
reader_writer_lock();
~reader_writer_lock
Destroys the reader_writer_lock object.
~reader_writer_lock();
Remarks
It is expected that the lock is no longer held when the destructor runs. Allowing the reader writer lock to destruct with the lock still held results in undefined behavior.
reader_writer_lock::scoped_lock Class
An exception safe RAII wrapper that can be used to acquire reader_writer_lock lock objects as a writer.
class scoped_lock;
scoped_lock::scoped_lock
Constructs a scoped_lock object and acquires the reader_writer_lock object passed in the _Reader_writer_lock parameter as a writer. If the lock is held by another thread, this call will block.
explicit _CRTIMP scoped_lock(reader_writer_lock& _Reader_writer_lock);
Parameters
_Reader_writer_lock
The reader_writer_lock object to acquire as a writer.
scoped_lock::~scoped_lock
Destroys a reader_writer_lock object and releases the lock supplied in its constructor.
~scoped_lock();
reader_writer_lock::scoped_lock_read Class
An exception safe RAII wrapper that can be used to acquire reader_writer_lock lock objects as a reader.
class scoped_lock_read;
scoped_lock_read::scoped_lock_read
Constructs a scoped_lock_read object and acquires the reader_writer_lock object passed in the _Reader_writer_lock parameter as a reader. If the lock is held by another thread as a writer or there are pending writers, this call will block.
explicit _CRTIMP scoped_lock_read(reader_writer_lock& _Reader_writer_lock);
Parameters
_Reader_writer_lock
The reader_writer_lock object to acquire as a reader.
reader_writer_lock::scoped_lock_read::~scoped_lock_read Destructor
Destroys a scoped_lock_read object and releases the lock supplied in its constructor.
~scoped_lock_read();
try_lock
Attempts to acquire the reader-writer lock as a writer without blocking.
Syntax
bool try_lock();
Return Value
If the lock was acquired, the value true; otherwise, the value false.
try_lock_read
Attempts to acquire the reader-writer lock as a reader without blocking.
bool try_lock_read();
Return Value
If the lock was acquired, the value true; otherwise, the value false.
unlock
Unlocks the reader-writer lock based on who locked it, reader or writer.
void unlock();
Remarks
If there are writers waiting on the lock, the release of the lock will always go to the next writer in FIFO order. This lock is biased towards writers and can starve readers under a continuous load of writers.