Implements a many-readers, single-writer locking concept. More...

#include <reader_writer_lock.hpp>

Collaboration diagram for m::reader_writer_mutex:

Public Member Functions
void	notify_readers ()

void	notify_writer ()

void	lock_read ()
	Acquire a read lock.

void	lock_write ()
	Acquire the write lock.

bool	try_lock_read ()
	Attempts to immediatly claim a read lock.

bool	try_lock_write ()
	Attempts to immediatly claim the exclusive write lock.

bool	upgrade ()
	Tries to upgrade a read lock to the write lock.

void	unlock_read ()

void	unlock_write ()

Private Attributes
std::mutex	mutex_
	The mutex to guard operations on members of this class.

detail::reader_writer_mutex_internal	rw_
	Represents the internal state of the reader-writer mutex.

std::condition_variable	cv_readers_
	Used to signal the respective class of clients that the resource has become available.

std::condition_variable	cv_writers_

Detailed Description

Implements a many-readers, single-writer locking concept.

NOTE: This class is thread-safe.

Definition at line 117 of file reader_writer_lock.hpp.

Member Function Documentation

◆ lock_read()

void m::reader_writer_mutex::lock_read ( )

inline

Acquire a read lock.

This call blocks the calling thread until a read lock was acquired.

Definition at line 143 of file reader_writer_lock.hpp.

References m::detail::reader_writer_mutex_internal::acquire_read_lock(), m::detail::reader_writer_mutex_internal::can_acquire_read_lock(), cv_readers_, M_insist, mutex_, m::detail::reader_writer_mutex_internal::request_read_lock(), and rw_.

◆ lock_write()

void m::reader_writer_mutex::lock_write ( )

inline

Acquire the write lock.

This call blocks the calling thread until the write lock was acquired.

Definition at line 152 of file reader_writer_lock.hpp.

References m::detail::reader_writer_mutex_internal::acquire_write_lock(), m::detail::reader_writer_mutex_internal::can_acquire_write_lock(), cv_writers_, M_insist, mutex_, m::detail::reader_writer_mutex_internal::request_write_lock(), and rw_.

◆ notify_readers()

void m::reader_writer_mutex::notify_readers ( )

inline

Definition at line 139 of file reader_writer_lock.hpp.

References cv_readers_.

Referenced by unlock_write().

◆ notify_writer()

void m::reader_writer_mutex::notify_writer ( )

inline

Definition at line 140 of file reader_writer_lock.hpp.

References cv_writers_.

Referenced by unlock_read(), and unlock_write().

◆ try_lock_read()

bool m::reader_writer_mutex::try_lock_read ( )

inline

Attempts to immediatly claim a read lock.

Returns true on success, false otherwise.

Definition at line 161 of file reader_writer_lock.hpp.

References m::detail::reader_writer_mutex_internal::acquire_read_lock(), m::detail::reader_writer_mutex_internal::can_acquire_read_lock(), mutex_, m::detail::reader_writer_mutex_internal::request_read_lock(), and rw_.

◆ try_lock_write()

bool m::reader_writer_mutex::try_lock_write ( )

inline

Attempts to immediatly claim the exclusive write lock.

Returns true on success, false otherwise.

Definition at line 171 of file reader_writer_lock.hpp.

References m::detail::reader_writer_mutex_internal::acquire_write_lock(), m::detail::reader_writer_mutex_internal::can_acquire_write_lock(), mutex_, m::detail::reader_writer_mutex_internal::request_write_lock(), and rw_.

◆ unlock_read()

void m::reader_writer_mutex::unlock_read ( )

inline

Definition at line 205 of file reader_writer_lock.hpp.

References m::and, M_insist, mutex_, notify_writer(), m::detail::reader_writer_mutex_internal::reader_wants_upgrade(), m::detail::reader_writer_mutex_internal::readers_active(), m::detail::reader_writer_mutex_internal::release_read_lock(), rw_, and m::detail::reader_writer_mutex_internal::writers_waiting().

◆ unlock_write()

void m::reader_writer_mutex::unlock_write ( )

inline

Definition at line 221 of file reader_writer_lock.hpp.

References m::and, M_insist, mutex_, notify_readers(), notify_writer(), m::detail::reader_writer_mutex_internal::readers_active(), m::detail::reader_writer_mutex_internal::readers_waiting(), m::detail::reader_writer_mutex_internal::release_write_lock(), rw_, and m::detail::reader_writer_mutex_internal::writers_waiting().

◆ upgrade()

bool m::reader_writer_mutex::upgrade ( )

inline

Tries to upgrade a read lock to the write lock.

This operation fails if another thread has already requested an upgrade.

WARNING: This operation is dangerous, as misuse can easily lead to a deadlock!

If two threads both hold a read lock and then both want to upgrade, one thread will succeed and one will fail. The succeeding thread will start to wait for the upgrade, i.e., until it is the single last active reader. If the other thread, that failed to upgrade, holds on to its read lock, the two threads deadlock.

A fair solution to this problem is to have the reader that failed to upgrade give up its read lock. This behavior is implemented by reader_writer_lock::upgrade().

Definition at line 193 of file reader_writer_lock.hpp.

References m::detail::reader_writer_mutex_internal::can_upgrade_lock(), cv_writers_, M_insist, mutex_, m::detail::reader_writer_mutex_internal::reader_wants_upgrade(), rw_, m::detail::reader_writer_mutex_internal::try_request_upgrade(), and m::detail::reader_writer_mutex_internal::upgrade_lock().

Field Documentation

◆ cv_readers_

std::condition_variable m::reader_writer_mutex::cv_readers_

private

Used to signal the respective class of clients that the resource has become available.

NOTE: Clients are not waiting for mutex_ to become available, but for the reader_writer_mutex to become available. These are two different things.

Definition at line 136 of file reader_writer_lock.hpp.

Referenced by lock_read(), and notify_readers().