/*
* 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/ThreadedExecutor.h"
#include "zthread/Guard.h"
#include "zthread/FastMutex.h"
#include "zthread/Time.h"
#include "ThreadImpl.h"
namespace ZThread {
namespace {
//!
class WaiterQueue {
typedef std::deque<ThreadImpl*> ThreadList;
typedef struct group_t {
size_t id;
size_t count;
ThreadList waiters;
group_t(size_t n) : id(n), count(0) {}
} Group;
typedef std::deque<Group> GroupList;
//! Predicate to find a specific group
struct by_id : public std::unary_function<bool, Group> {
size_t id;
by_id(size_t n) : id(n) {}
bool operator()(const Group& grp) {
return grp.id == id;
}
};
//! Functor to count groups
struct counter : public std::unary_function<void, Group> {
size_t count;
counter() : count(0) {}
void operator()(const Group& grp) { count += grp.count; }
operator size_t() { return count; }
};
FastMutex _lock;
GroupList _list;
size_t _id;
size_t _generation;
public:
WaiterQueue() : _id(0), _generation(0) {
// At least one empty-group exists
_list.push_back( Group(_id++) );
}
/**
* Insert the current thread into the current waiter list
*
* @pre At least one empty group exists
* @post At least one empty group exists
*/
bool wait(unsigned long timeout) {
ThreadImpl* self = ThreadImpl::current();
Monitor& m = self->getMonitor();
Monitor::STATE state;
Guard<Lockable> g1(_lock);
// At least one empty-group exists
assert(!_list.empty());
// Return w/o waiting if there are no executing tasks
if((size_t)std::for_each(_list.begin(), _list.end(), counter()) < 1)
return true;
// Update the waiter list for the active group
_list.back().waiters.push_back(self);
size_t n = _list.back().id;
m.acquire();
{
Guard<Lockable, UnlockedScope> g2(g1);
state = timeout == 0 ? m.wait() : m.wait(timeout);
}
m.release();
// If awoke due to a reason other than the last task in the group 'n' completing,
// then then find the group 'self' is waiting in
GroupList::iterator i = std::find_if(_list.begin(), _list.end(), by_id(n));
if(i != _list.end()) {
// Remove 'self' from that list if it is still a member
ThreadList::iterator j = std::find(i->waiters.begin(), i->waiters.end(), self);
if(j != i->waiters.end())
i->waiters.erase(j);
}
// At least one empty-group exists
assert(!_list.empty());
switch(state) {
case Monitor::SIGNALED:
break;
case Monitor::TIMEDOUT:
return false;
case Monitor::INTERRUPTED:
throw Interrupted_Exception();
default:
throw Synchronization_Exception();
}
return true;
}
/**
* Increment the active group count
*
* @pre at least 1 empty group exists
* @post at least 1 non-empty group exists
*/
std::pair<size_t, size_t> increment() {
Guard<FastMutex> g(_lock);
// At least one empty-group exists
assert(!_list.empty());
GroupList::iterator i = --_list.end();
size_t n = i->id;
if(i == _list.end()) {
// A group should never have been removed until
// the final task in that group completed
assert(0);
}
i->count++;
// When the active group is being incremented, insert a new active group
// to replace it if there were waiting threads
if(i == --_list.end() && !i->waiters.empty())
_list.push_back(Group(_id++));
// At least 1 non-empty group exists
assert((size_t)std::for_each(_list.begin(), _list.end(), counter()) > 0);
return std::make_pair(n, _generation);
}
/**
* Decrease the count for the group with the given id.
*
* @param n group id
*
* @pre At least 1 non-empty group exists
* @post At least 1 empty group exists
*/
void decrement(size_t n) {
Guard<FastMutex> g1(_lock);
// At least 1 non-empty group exists
assert((size_t)std::for_each(_list.begin(), _list.end(), counter()) > 0);
// Find the requested group
GroupList::iterator i = std::find_if(_list.begin(), _list.end(), by_id(n));
if(i == _list.end()) {
// A group should never have been removed until
// the final task in that group completed
assert(0);
}
// Decrease the count for tasks in this group,
if(--i->count == 0 && i == _list.begin()) {
do {
// When the first group completes, wake all waiters for every
// group, starting from the first until a group that is not
// complete is reached
/*
// Don't remove the empty active group
if(i == --_list.end() && i->waiters.empty())
break;
*/
if( awaken(*i) ) {
// If all waiters were awakened, remove the group
i = _list.erase(i);
} else {
{
// Otherwise, unlock and yield allowing the waiter
// lists to be updated if other threads are busy
Guard<FastLock, UnlockedScope> g2(g1);
ThreadImpl::yield();
}
i = _list.begin();
}
} while(i != _list.end() && i->count == 0);
// Ensure that an active group exists
if(_list.empty())
_list.push_back( Group(++_id) );
}
// At least one group exists
assert(!_list.empty());
}
/**
*/
size_t generation(bool next = false) {
Guard<FastMutex> g(_lock);
return next ? _generation++ : _generation;
}
private:
/**
* Awaken all the waiters remaining in the given group
*
* @return
* - true if all the waiting threads were successfully awakened.
* - false if there were one or more threads that could not be awakened.
*/
bool awaken(Group& grp) {
// Go through the waiter list in the given group;
for(ThreadList::iterator i = grp.waiters.begin(); i != grp.waiters.end();) {
ThreadImpl* impl = *i;
Monitor& m = impl->getMonitor();
// Try the monitor lock, if it cant be locked skip to the next waiter
if(m.tryAcquire()) {
// Notify the monitor & remove from the waiter list so time isn't
// wasted checking it again.
i = grp.waiters.erase(i);
// Try to wake the waiter, it doesn't matter if this is successful
// or not (only fails when the monitor is already going to stop waiting).
m.notify();
m.release();
} else ++i;
}
return grp.waiters.empty();
}
};
//! Synchronization point for the Executor
class ExecutorImpl {
typedef std::deque<ThreadImpl*> ThreadList;
bool _canceled;
FastMutex _lock;
//! Worker threads
ThreadList _threads;
WaiterQueue _queue;
public:
ExecutorImpl() : _canceled(false) {}
WaiterQueue& getWaiterQueue() {
return _queue;
}
void registerThread(size_t generation) {
// Interrupt slow starting threads
if(getWaiterQueue().generation() != generation)
ThreadImpl::current()->interrupt();
// Enqueue for possible future interrupt()
else {
Guard<FastMutex> g(_lock);
_threads.push_back( ThreadImpl::current() );
}
}
void unregisterThread() {
Guard<FastMutex> g(_lock);
std::remove(_threads.begin(), _threads.end(), ThreadImpl::current() );
}
void cancel() {
Guard<FastMutex> g(_lock);
_canceled = true;
}
bool isCanceled() {
if(_canceled)
return true;
Guard<FastMutex> g(_lock);
return _canceled;
}
void interrupt() {
Guard<FastMutex> g(_lock);
// Interrupt all the registered threads
for(ThreadList::iterator i = _threads.begin(); i != _threads.end(); ++i)
(*i)->interrupt();
// Bump the generation up, ensuring slow starting threads get this interrupt
getWaiterQueue().generation( true );
}
}; /* ExecutorImpl */
//! Wrap a generation and a group around a task
class Worker : public Runnable {
CountedPtr< ExecutorImpl > _impl;
Task _task;
size_t _generation;
size_t _group;
public:
Worker(const CountedPtr< ExecutorImpl >& impl, const Task& task)
: _impl(impl), _task(task) {
std::pair<size_t, size_t> pr( _impl->getWaiterQueue().increment() );
_group = pr.first;
_generation = pr.second;
}
size_t group() const {
return _group;
}
size_t generation() const {
return _generation;
}
void run() {
// Register this thread once its begun; the generation is used to ensure
// threads that are slow starting are properly interrupted
_impl->registerThread( generation() );
try {
_task->run();
} catch(...) {
/* consume the exceptions the work propogates */
}
_impl->getWaiterQueue().decrement( group() );
// Unregister this thread
_impl->unregisterThread();
}
}; /* Worker */
}
ThreadedExecutor::ThreadedExecutor() : _impl(new ExecutorImpl) {}
ThreadedExecutor::~ThreadedExecutor() {}
void ThreadedExecutor::execute(const Task& task) {
Thread t( new Worker(_impl, task) );
}
void ThreadedExecutor::interrupt() {
_impl->interrupt();
}
void ThreadedExecutor::cancel() {
_impl->cancel();
}
bool ThreadedExecutor::isCanceled() {
return _impl->isCanceled();
}
void ThreadedExecutor::wait() {
_impl->getWaiterQueue().wait(0);
}
bool ThreadedExecutor::wait(unsigned long timeout) {
return _impl->getWaiterQueue().wait(timeout == 0 ? 1 : timeout);
}
}
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