boost/interprocess/sync/interprocess_upgradable_mutex.hpp
////////////////////////////////////////////////////////////////////////////////
//
// Code based on Howard Hinnant's upgrade_mutex class
//
// (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTERPROCESS_UPGRADABLE_MUTEX_HPP
#define BOOST_INTERPROCESS_UPGRADABLE_MUTEX_HPP
#if (defined _MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif
#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/interprocess/sync/scoped_lock.hpp>
#include <boost/interprocess/detail/posix_time_types_wrk.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/interprocess/sync/interprocess_condition.hpp>
#include <climits>
//!\file
//!Describes interprocess_upgradable_mutex class
namespace boost {
namespace interprocess {
//!Wraps a interprocess_upgradable_mutex that can be placed in shared memory and can be
//!shared between processes. Allows timed lock tries
class interprocess_upgradable_mutex
{
//Non-copyable
interprocess_upgradable_mutex(const interprocess_upgradable_mutex &);
interprocess_upgradable_mutex &operator=(const interprocess_upgradable_mutex &);
friend class interprocess_condition;
public:
//!Constructs the upgradable lock.
//!Throws interprocess_exception on error.
interprocess_upgradable_mutex();
//!Destroys the upgradable lock.
//!Does not throw.
~interprocess_upgradable_mutex();
//Exclusive locking
//!Effects: The calling thread tries to obtain exclusive ownership of the mutex,
//! and if another thread has exclusive, sharable or upgradable ownership of
//! the mutex, it waits until it can obtain the ownership.
//!Throws: interprocess_exception on error.
void lock();
//!Effects: The calling thread tries to acquire exclusive ownership of the mutex
//! without waiting. If no other thread has exclusive, sharable or upgradable
//! ownership of the mutex this succeeds.
//!Returns: If it can acquire exclusive ownership immediately returns true.
//! If it has to wait, returns false.
//!Throws: interprocess_exception on error.
bool try_lock();
//!Effects: The calling thread tries to acquire exclusive ownership of the mutex
//! waiting if necessary until no other thread has exclusive, sharable or
//! upgradable ownership of the mutex or abs_time is reached.
//!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
//!Throws: interprocess_exception on error.
bool timed_lock(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have exclusive ownership of the mutex.
//!Effects: The calling thread releases the exclusive ownership of the mutex.
//!Throws: An exception derived from interprocess_exception on error.
void unlock();
//Sharable locking
//!Effects: The calling thread tries to obtain sharable ownership of the mutex,
//! and if another thread has exclusive ownership of the mutex,
//! waits until it can obtain the ownership.
//!Throws: interprocess_exception on error.
void lock_sharable();
//!Effects: The calling thread tries to acquire sharable ownership of the mutex
//! without waiting. If no other thread has exclusive ownership
//! of the mutex this succeeds.
//!Returns: If it can acquire sharable ownership immediately returns true. If it
//! has to wait, returns false.
//!Throws: interprocess_exception on error.
bool try_lock_sharable();
//!Effects: The calling thread tries to acquire sharable ownership of the mutex
//! waiting if necessary until no other thread has exclusive
//! ownership of the mutex or abs_time is reached.
//!Returns: If acquires sharable ownership, returns true. Otherwise returns false.
//!Throws: interprocess_exception on error.
bool timed_lock_sharable(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have sharable ownership of the mutex.
//!Effects: The calling thread releases the sharable ownership of the mutex.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_sharable();
//Upgradable locking
//!Effects: The calling thread tries to obtain upgradable ownership of the mutex,
//! and if another thread has exclusive or upgradable ownership of the mutex,
//! waits until it can obtain the ownership.
//!Throws: interprocess_exception on error.
void lock_upgradable();
//!Effects: The calling thread tries to acquire upgradable ownership of the mutex
//! without waiting. If no other thread has exclusive or upgradable ownership
//! of the mutex this succeeds.
//!Returns: If it can acquire upgradable ownership immediately returns true.
//! If it has to wait, returns false.
//!Throws: interprocess_exception on error.
bool try_lock_upgradable();
//!Effects: The calling thread tries to acquire upgradable ownership of the mutex
//! waiting if necessary until no other thread has exclusive or upgradable
//! ownership of the mutex or abs_time is reached.
//!Returns: If acquires upgradable ownership, returns true. Otherwise returns false.
//!Throws: interprocess_exception on error.
bool timed_lock_upgradable(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have upgradable ownership of the mutex.
//!Effects: The calling thread releases the upgradable ownership of the mutex.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_upgradable();
//Demotions
//!Precondition: The thread must have exclusive ownership of the mutex.
//!Effects: The thread atomically releases exclusive ownership and acquires
//! upgradable ownership. This operation is non-blocking.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_and_lock_upgradable();
//!Precondition: The thread must have exclusive ownership of the mutex.
//!Effects: The thread atomically releases exclusive ownership and acquires
//! sharable ownership. This operation is non-blocking.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_and_lock_sharable();
//!Precondition: The thread must have upgradable ownership of the mutex.
//!Effects: The thread atomically releases upgradable ownership and acquires
//! sharable ownership. This operation is non-blocking.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_upgradable_and_lock_sharable();
//Promotions
//!Precondition: The thread must have upgradable ownership of the mutex.
//!Effects: The thread atomically releases upgradable ownership and acquires
//! exclusive ownership. This operation will block until all threads with
//! sharable ownership release their sharable lock.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_upgradable_and_lock();
//!Precondition: The thread must have upgradable ownership of the mutex.
//!Effects: The thread atomically releases upgradable ownership and tries to
//! acquire exclusive ownership. This operation will fail if there are threads
//! with sharable ownership, but it will maintain upgradable ownership.
//!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
//!Throws: An exception derived from interprocess_exception on error.
bool try_unlock_upgradable_and_lock();
//!Precondition: The thread must have upgradable ownership of the mutex.
//!Effects: The thread atomically releases upgradable ownership and tries to acquire
//! exclusive ownership, waiting if necessary until abs_time. This operation will
//! fail if there are threads with sharable ownership or timeout reaches, but it
//! will maintain upgradable ownership.
//!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
//!Throws: An exception derived from interprocess_exception on error. */
bool timed_unlock_upgradable_and_lock(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have sharable ownership of the mutex.
//!Effects: The thread atomically releases sharable ownership and tries to acquire
//! exclusive ownership. This operation will fail if there are threads with sharable
//! or upgradable ownership, but it will maintain sharable ownership.
//!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
//!Throws: An exception derived from interprocess_exception on error.
bool try_unlock_sharable_and_lock();
//!Precondition: The thread must have sharable ownership of the mutex.
//!Effects: The thread atomically releases sharable ownership and tries to acquire
//! upgradable ownership. This operation will fail if there are threads with sharable
//! or upgradable ownership, but it will maintain sharable ownership.
//!Returns: If acquires upgradable ownership, returns true. Otherwise returns false.
//!Throws: An exception derived from interprocess_exception on error.
bool try_unlock_sharable_and_lock_upgradable();
/// @cond
private:
typedef scoped_lock<interprocess_mutex> scoped_lock_t;
//Pack all the control data in a word to be able
//to use atomic instructions in the future
struct control_word_t
{
unsigned exclusive_in : 1;
unsigned upgradable_in : 1;
unsigned num_upr_shar : sizeof(unsigned)*CHAR_BIT-2;
} m_ctrl;
interprocess_mutex m_mut;
interprocess_condition m_first_gate;
interprocess_condition m_second_gate;
private:
//Rollback structures for exceptions or failure return values
struct exclusive_rollback
{
exclusive_rollback(control_word_t &ctrl
,interprocess_condition &first_gate)
: mp_ctrl(&ctrl), m_first_gate(first_gate)
{}
void release()
{ mp_ctrl = 0; }
~exclusive_rollback()
{
if(mp_ctrl){
mp_ctrl->exclusive_in = 0;
m_first_gate.notify_all();
}
}
control_word_t *mp_ctrl;
interprocess_condition &m_first_gate;
};
struct upgradable_to_exclusive_rollback
{
upgradable_to_exclusive_rollback(control_word_t &ctrl)
: mp_ctrl(&ctrl)
{}
void release()
{ mp_ctrl = 0; }
~upgradable_to_exclusive_rollback()
{
if(mp_ctrl){
//Recover upgradable lock
mp_ctrl->upgradable_in = 1;
++mp_ctrl->num_upr_shar;
//Execute the second half of exclusive locking
mp_ctrl->exclusive_in = 0;
}
}
control_word_t *mp_ctrl;
};
template<int Dummy>
struct base_constants_t
{
static const unsigned max_readers
= ~(unsigned(3) << (sizeof(unsigned)*CHAR_BIT-2));
};
typedef base_constants_t<0> constants;
/// @endcond
};
/// @cond
template <int Dummy>
const unsigned interprocess_upgradable_mutex::base_constants_t<Dummy>::max_readers;
inline interprocess_upgradable_mutex::interprocess_upgradable_mutex()
{
this->m_ctrl.exclusive_in = 0;
this->m_ctrl.upgradable_in = 0;
this->m_ctrl.num_upr_shar = 0;
}
inline interprocess_upgradable_mutex::~interprocess_upgradable_mutex()
{}
inline void interprocess_upgradable_mutex::lock()
{
scoped_lock_t lock(m_mut);
//The exclusive lock must block in the first gate
//if an exclusive or upgradable lock has been acquired
while (this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in){
this->m_first_gate.wait(lock);
}
//Mark that exclusive lock has been acquired
this->m_ctrl.exclusive_in = 1;
//Prepare rollback
exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
//Now wait until all readers are gone
while (this->m_ctrl.num_upr_shar){
this->m_second_gate.wait(lock);
}
rollback.release();
}
inline bool interprocess_upgradable_mutex::try_lock()
{
scoped_lock_t lock(m_mut, try_to_lock);
//If we can't lock or any has there is any exclusive, upgradable
//or sharable mark return false;
if(!lock.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.num_upr_shar){
return false;
}
this->m_ctrl.exclusive_in = 1;
return true;
}
inline bool interprocess_upgradable_mutex::timed_lock
(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->lock();
return true;
}
scoped_lock_t lock(m_mut, abs_time);
if(!lock.owns()) return false;
//The exclusive lock must block in the first gate
//if an exclusive or upgradable lock has been acquired
while (this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in){
if(!this->m_first_gate.timed_wait(lock, abs_time)){
if(this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in){
return false;
}
break;
}
}
//Mark that exclusive lock has been acquired
this->m_ctrl.exclusive_in = 1;
//Prepare rollback
exclusive_rollback rollback(this->m_ctrl, this->m_first_gate);
//Now wait until all readers are gone
while (this->m_ctrl.num_upr_shar){
if(!this->m_second_gate.timed_wait(lock, abs_time)){
if(this->m_ctrl.num_upr_shar){
return false;
}
break;
}
}
rollback.release();
return true;
}
inline void interprocess_upgradable_mutex::unlock()
{
scoped_lock_t lock(m_mut);
this->m_ctrl.exclusive_in = 0;
this->m_first_gate.notify_all();
}
//Upgradable locking
inline void interprocess_upgradable_mutex::lock_upgradable()
{
scoped_lock_t lock(m_mut);
//The upgradable lock must block in the first gate
//if an exclusive or upgradable lock has been acquired
//or there are too many sharable locks
while(this->m_ctrl.exclusive_in || this->m_ctrl.upgradable_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
this->m_first_gate.wait(lock);
}
//Mark that upgradable lock has been acquired
//And add upgradable to the sharable count
this->m_ctrl.upgradable_in = 1;
++this->m_ctrl.num_upr_shar;
}
inline bool interprocess_upgradable_mutex::try_lock_upgradable()
{
scoped_lock_t lock(m_mut, try_to_lock);
//The upgradable lock must fail
//if an exclusive or upgradable lock has been acquired
//or there are too many sharable locks
if(!lock.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.upgradable_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
return false;
}
//Mark that upgradable lock has been acquired
//And add upgradable to the sharable count
this->m_ctrl.upgradable_in = 1;
++this->m_ctrl.num_upr_shar;
return true;
}
inline bool interprocess_upgradable_mutex::timed_lock_upgradable
(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->lock_upgradable();
return true;
}
scoped_lock_t lock(m_mut, abs_time);
if(!lock.owns()) return false;
//The upgradable lock must block in the first gate
//if an exclusive or upgradable lock has been acquired
//or there are too many sharable locks
while(this->m_ctrl.exclusive_in
|| this->m_ctrl.upgradable_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
if(!this->m_first_gate.timed_wait(lock, abs_time)){
if((this->m_ctrl.exclusive_in
|| this->m_ctrl.upgradable_in
|| this->m_ctrl.num_upr_shar == constants::max_readers)){
return false;
}
break;
}
}
//Mark that upgradable lock has been acquired
//And add upgradable to the sharable count
this->m_ctrl.upgradable_in = 1;
++this->m_ctrl.num_upr_shar;
return true;
}
inline void interprocess_upgradable_mutex::unlock_upgradable()
{
scoped_lock_t lock(m_mut);
//Mark that upgradable lock has been acquired
//And add upgradable to the sharable count
this->m_ctrl.upgradable_in = 0;
--this->m_ctrl.num_upr_shar;
this->m_first_gate.notify_all();
}
//Sharable locking
inline void interprocess_upgradable_mutex::lock_sharable()
{
scoped_lock_t lock(m_mut);
//The sharable lock must block in the first gate
//if an exclusive lock has been acquired
//or there are too many sharable locks
while(this->m_ctrl.exclusive_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
this->m_first_gate.wait(lock);
}
//Increment sharable count
++this->m_ctrl.num_upr_shar;
}
inline bool interprocess_upgradable_mutex::try_lock_sharable()
{
scoped_lock_t lock(m_mut, try_to_lock);
//The sharable lock must fail
//if an exclusive lock has been acquired
//or there are too many sharable locks
if(!lock.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
return false;
}
//Increment sharable count
++this->m_ctrl.num_upr_shar;
return true;
}
inline bool interprocess_upgradable_mutex::timed_lock_sharable
(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->lock_sharable();
return true;
}
scoped_lock_t lock(m_mut, abs_time);
if(!lock.owns()) return false;
//The sharable lock must block in the first gate
//if an exclusive lock has been acquired
//or there are too many sharable locks
while (this->m_ctrl.exclusive_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
if(!this->m_first_gate.timed_wait(lock, abs_time)){
if(this->m_ctrl.exclusive_in
|| this->m_ctrl.num_upr_shar == constants::max_readers){
return false;
}
break;
}
}
//Increment sharable count
++this->m_ctrl.num_upr_shar;
return true;
}
inline void interprocess_upgradable_mutex::unlock_sharable()
{
scoped_lock_t lock(m_mut);
//Decrement sharable count
--this->m_ctrl.num_upr_shar;
if (this->m_ctrl.num_upr_shar == 0){
this->m_second_gate.notify_one();
}
//Check if there are blocked sharables because of
//there were too many sharables
else if(this->m_ctrl.num_upr_shar == (constants::max_readers-1)){
this->m_first_gate.notify_all();
}
}
//Downgrading
inline void interprocess_upgradable_mutex::unlock_and_lock_upgradable()
{
scoped_lock_t lock(m_mut);
//Unmark it as exclusive
this->m_ctrl.exclusive_in = 0;
//Mark it as upgradable
this->m_ctrl.upgradable_in = 1;
//The sharable count should be 0 so increment it
this->m_ctrl.num_upr_shar = 1;
//Notify readers that they can enter
m_first_gate.notify_all();
}
inline void interprocess_upgradable_mutex::unlock_and_lock_sharable()
{
scoped_lock_t lock(m_mut);
//Unmark it as exclusive
this->m_ctrl.exclusive_in = 0;
//The sharable count should be 0 so increment it
this->m_ctrl.num_upr_shar = 1;
//Notify readers that they can enter
m_first_gate.notify_all();
}
inline void interprocess_upgradable_mutex::unlock_upgradable_and_lock_sharable()
{
scoped_lock_t lock(m_mut);
//Unmark it as upgradable (we don't have to decrement count)
this->m_ctrl.upgradable_in = 0;
//Notify readers/upgradable that they can enter
m_first_gate.notify_all();
}
//Upgrading
inline void interprocess_upgradable_mutex::unlock_upgradable_and_lock()
{
scoped_lock_t lock(m_mut);
//Simulate unlock_upgradable() without
//notifying sharables.
this->m_ctrl.upgradable_in = 0;
--this->m_ctrl.num_upr_shar;
//Execute the second half of exclusive locking
this->m_ctrl.exclusive_in = 1;
//Prepare rollback
upgradable_to_exclusive_rollback rollback(m_ctrl);
while (this->m_ctrl.num_upr_shar){
this->m_second_gate.wait(lock);
}
rollback.release();
}
inline bool interprocess_upgradable_mutex::try_unlock_upgradable_and_lock()
{
scoped_lock_t lock(m_mut, try_to_lock);
//Check if there are no readers
if(!lock.owns()
|| this->m_ctrl.num_upr_shar != 1){
return false;
}
//Now unlock upgradable and mark exclusive
this->m_ctrl.upgradable_in = 0;
--this->m_ctrl.num_upr_shar;
this->m_ctrl.exclusive_in = 1;
return true;
}
inline bool interprocess_upgradable_mutex::timed_unlock_upgradable_and_lock
(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->unlock_upgradable_and_lock();
return true;
}
scoped_lock_t lock(m_mut, abs_time);
if(!lock.owns()) return false;
//Simulate unlock_upgradable() without
//notifying sharables.
this->m_ctrl.upgradable_in = 0;
--this->m_ctrl.num_upr_shar;
//Execute the second half of exclusive locking
this->m_ctrl.exclusive_in = 1;
//Prepare rollback
upgradable_to_exclusive_rollback rollback(m_ctrl);
while (this->m_ctrl.num_upr_shar){
if(!this->m_second_gate.timed_wait(lock, abs_time)){
if(this->m_ctrl.num_upr_shar){
return false;
}
break;
}
}
rollback.release();
return true;
}
inline bool interprocess_upgradable_mutex::try_unlock_sharable_and_lock()
{
scoped_lock_t lock(m_mut, try_to_lock);
//If we can't lock or any has there is any exclusive, upgradable
//or sharable mark return false;
if(!lock.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.upgradable_in
|| this->m_ctrl.num_upr_shar != 1){
return false;
}
this->m_ctrl.exclusive_in = 1;
this->m_ctrl.num_upr_shar = 0;
return true;
}
inline bool interprocess_upgradable_mutex::try_unlock_sharable_and_lock_upgradable()
{
scoped_lock_t lock(m_mut, try_to_lock);
//The upgradable lock must fail
//if an exclusive or upgradable lock has been acquired
if(!lock.owns()
|| this->m_ctrl.exclusive_in
|| this->m_ctrl.upgradable_in){
return false;
}
//Mark that upgradable lock has been acquired
this->m_ctrl.upgradable_in = 1;
return true;
}
/// @endcond
} //namespace interprocess {
} //namespace boost {
#include <boost/interprocess/detail/config_end.hpp>
#endif //BOOST_INTERPROCESS_UPGRADABLE_MUTEX_HPP