mirror of
https://github.com/mangosfour/server.git
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377 lines
9.4 KiB
C++
377 lines
9.4 KiB
C++
/*
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* Copyright (c) 2005, Eric Crahen
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is furnished
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* to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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*/
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#include "zthread/Exceptions.h"
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#include "zthread/Guard.h"
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#include "Debug.h"
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#include "FastLock.h"
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#include "Scheduling.h"
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#include <assert.h>
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#include <errno.h>
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namespace ZThread {
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/**
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* @author Eric Crahen <http://www.code-foo.com>
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* @date <2003-07-16T19:52:12-0400>
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* @version 2.2.11
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* @class NullBehavior
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*/
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class NullBehavior {
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protected:
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inline void waiterArrived(ThreadImpl*) { }
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inline void waiterDeparted(ThreadImpl*) { }
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inline void ownerAcquired(ThreadImpl*) { }
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inline void ownerReleased(ThreadImpl*) { }
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};
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/**
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* @author Eric Crahen <http://www.code-foo.com>
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* @date <2003-07-16T19:52:12-0400>
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* @version 2.2.11
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* @class MutexImpl
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*
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* The MutexImpl template allows how waiter lists are sorted, and
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* what actions are taken when a thread interacts with the mutex
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* to be parametized.
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*/
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template <typename List, typename Behavior>
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class MutexImpl : Behavior {
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//! List of Events that are waiting for notification
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List _waiters;
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//! Serialize access to this Mutex
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FastLock _lock;
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//! Current owner
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volatile ThreadImpl* _owner;
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public:
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/**
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* Create a new MutexImpl
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*
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* @exception Initialization_Exception thrown if resources could not be
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* properly allocated
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*/
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MutexImpl() : _owner(0) { }
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~MutexImpl();
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void acquire();
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void release();
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bool tryAcquire(unsigned long timeout);
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};
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/**
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* Destroy this MutexImpl and release its resources
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*/
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template<typename List, typename Behavior>
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MutexImpl<List, Behavior>::~MutexImpl() {
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#ifndef NDEBUG
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// It is an error to destroy a mutex that has not been released
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if(_owner != 0) {
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ZTDEBUG("** You are destroying a mutex which was never released. **\n");
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assert(0); // Destroyed mutex while in use
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}
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if(!_waiters.empty()) {
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ZTDEBUG("** You are destroying a mutex which is blocking %d threads. **\n", _waiters.size());
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assert(0); // Destroyed mutex while in use
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}
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#endif
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}
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/**
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* Acquire a lock on the mutex. If this operation succeeds the calling
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* thread holds an exclusive lock on this mutex, otherwise it is blocked
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* until the lock can be acquired.
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*
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* @exception Deadlock_Exception thrown when the caller attempts to acquire() more
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* than once, If the checking flag is set.
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* @exception Interrupted_Exception thrown when the caller status is interrupted
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* @exception Synchronization_Exception thrown if there is some other error.
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*/
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template<typename List, typename Behavior>
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void MutexImpl<List, Behavior>::acquire() {
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ThreadImpl* self = ThreadImpl::current();
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Monitor& m = self->getMonitor();
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Monitor::STATE state;
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Guard<FastLock> g1(_lock);
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// Deadlock will occur if the current thread is the owner
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// and there is no entry count.
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if(_owner == self)
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throw Deadlock_Exception();
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// Acquire the lock if it is free and there are no waiting threads
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if(_owner == 0 && _waiters.empty()) {
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_owner = self;
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this->ownerAcquired(self);
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}
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// Otherwise, wait for a signal from a thread releasing its
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// ownership of the lock
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else {
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_waiters.insert(self);
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m.acquire();
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this->waiterArrived(self);
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{
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Guard<FastLock, UnlockedScope> g2(g1);
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state = m.wait();
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}
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this->waiterDeparted(self);
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m.release();
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// Remove from waiter list, regardless of wether release() is called or
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// not. The monitor is sticky, so its possible a state 'stuck' from a
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// previous operation and will leave the wait() w/o release() having
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// been called (e.g. interrupted)
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typename List::iterator i = std::find(_waiters.begin(), _waiters.end(), self);
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if(i != _waiters.end())
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_waiters.erase(i);
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// If awoke due to a notify(), take ownership.
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switch(state) {
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case Monitor::SIGNALED:
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assert(_owner == 0);
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_owner = self;
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this->ownerAcquired(self);
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break;
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case Monitor::INTERRUPTED:
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throw Interrupted_Exception();
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default:
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throw Synchronization_Exception();
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}
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}
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}
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/**
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* Acquire a lock on the mutex. If this operation succeeds the calling
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* thread holds an exclusive lock on this mutex. If the lock cannot be
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* obtained before the timeout expires, the caller returns false.
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*
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* @exception Deadlock_Exception thrown when the caller attempts to acquire() more
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* than once, If the checking flag is set.
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* @exception Interrupted_Exception thrown when the caller status is interrupted
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* @exception Synchronization_Exception thrown if there is some other error.
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*/
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template<typename List, typename Behavior>
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bool MutexImpl<List, Behavior>::tryAcquire(unsigned long timeout) {
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ThreadImpl* self = ThreadImpl::current();
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Monitor& m = self->getMonitor();
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Guard<FastLock> g1(_lock);
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// Deadlock will occur if the current thread is the owner
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// and there is no entry count.
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if(_owner == self)
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throw Deadlock_Exception();
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// Acquire the lock if it is free and there are no waiting threads
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if(_owner == 0 && _waiters.empty()) {
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_owner = self;
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this->ownerAcquired(self);
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}
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// Otherwise, wait for a signal from a thread releasing its
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// ownership of the lock
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else {
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_waiters.insert(self);
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Monitor::STATE state = Monitor::TIMEDOUT;
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// Don't bother waiting if the timeout is 0
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if(timeout) {
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m.acquire();
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this->waiterArrived(self);
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{
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Guard<FastLock, UnlockedScope> g2(g1);
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state = m.wait(timeout);
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}
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this->waiterDeparted(self);
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m.release();
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}
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// Remove from waiter list, regarless of weather release() is called or
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// not. The monitor is sticky, so its possible a state 'stuck' from a
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// previous operation and will leave the wait() w/o release() having
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// been called.
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typename List::iterator i = std::find(_waiters.begin(), _waiters.end(), self);
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if(i != _waiters.end())
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_waiters.erase(i);
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// If awoke due to a notify(), take ownership.
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switch(state) {
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case Monitor::SIGNALED:
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assert(0 == _owner);
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_owner = self;
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this->ownerAcquired(self);
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break;
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case Monitor::INTERRUPTED:
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throw Interrupted_Exception();
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case Monitor::TIMEDOUT:
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return false;
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default:
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throw Synchronization_Exception();
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}
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}
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return true;
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}
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/**
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* Release a lock on the mutex. If this operation succeeds the calling
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* thread no longer holds an exclusive lock on this mutex. If there are
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* waiting threads, one will be selected, assigned ownership and specifically
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* awakened.
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*
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* @exception InvalidOp_Exception - thrown if an attempt is made to
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* release a mutex not owned by the calling thread.
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*/
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template<typename List, typename Behavior>
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void MutexImpl<List, Behavior>::release() {
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ThreadImpl* impl = ThreadImpl::current();
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Guard<FastLock> g1(_lock);
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// Make sure the operation is valid
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if(_owner != impl)
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throw InvalidOp_Exception();
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_owner = 0;
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this->ownerReleased(impl);
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// Try to find a waiter with a backoff & retry scheme
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for(;;) {
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// Go through the list, attempt to notify() a waiter.
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for(typename List::iterator i = _waiters.begin(); i != _waiters.end();) {
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// Try the monitor lock, if it cant be locked skip to the next waiter
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impl = *i;
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Monitor& m = impl->getMonitor();
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if(m.tryAcquire()) {
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// If notify() is not sucessful, it is because the wait() has already
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// been ended (killed/interrupted/notify'd)
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bool woke = m.notify();
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m.release();
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// Once notify() succeeds, return
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if(woke)
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return;
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} else ++i;
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}
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if(_waiters.empty())
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return;
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{ // Backoff and try again
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Guard<FastLock, UnlockedScope> g2(g1);
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ThreadImpl::yield();
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}
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}
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}
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} // namespace ZThread
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