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