path: root/LibOVR/Src/Kernel/OVR_ThreadsWinAPI.cpp

/************************************************************************************

Filename    :   OVR_ThreadsWinAPI.cpp
Platform    :   WinAPI
Content     :   Windows specific thread-related (safe) functionality
Created     :   September 19, 2012
Notes       : 

Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.

Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License"); 
you may not use the Oculus VR Rift SDK except in compliance with the License, 
which is provided at the time of installation or download, or which 
otherwise accompanies this software in either electronic or hard copy form.

You may obtain a copy of the License at

http://www.oculusvr.com/licenses/LICENSE-3.2 

Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

************************************************************************************/

#include "OVR_Threads.h"
#include "OVR_Hash.h"
#include "OVR_Log.h"
#include "OVR_Timer.h"

#ifdef OVR_ENABLE_THREADS

// For _beginthreadex / _endtheadex
#include <process.h>

namespace OVR {


//-----------------------------------------------------------------------------------
// *** Internal Mutex implementation class

class MutexImpl : public NewOverrideBase
{
    // System mutex or semaphore
    HANDLE            hMutexOrSemaphore;
    bool              Recursive;
    volatile unsigned LockCount;
    
    friend class WaitConditionImpl;

public:
    // Constructor/destructor
    MutexImpl(bool recursive = 1);
    ~MutexImpl();

    // Locking functions
    void                DoLock();
    bool                TryLock();
    void                Unlock(Mutex* pmutex);
    // Returns 1 if the mutes is currently locked
    bool                IsLockedByAnotherThread(Mutex* pmutex);
};

// *** Constructor/destructor
MutexImpl::MutexImpl(bool recursive)
{    
    Recursive                   = recursive;
    LockCount                   = 0;
#if defined(OVR_OS_WIN32) // Older versions of Windows don't support CreateSemaphoreEx, so stick with CreateSemaphore for portability.
    hMutexOrSemaphore           = Recursive ? CreateMutex(NULL, 0, NULL) : CreateSemaphore(NULL, 1, 1, NULL);
#else
    // No CreateSemaphore() call, so emulate it.
    hMutexOrSemaphore           = Recursive ? CreateMutex(NULL, 0, NULL) : CreateSemaphoreEx(NULL, 1, 1, NULL, 0, SEMAPHORE_ALL_ACCESS);
#endif
}
MutexImpl::~MutexImpl()
{
    CloseHandle(hMutexOrSemaphore);
}


// Lock and try lock
void MutexImpl::DoLock()
{
    if (::WaitForSingleObject(hMutexOrSemaphore, INFINITE) != WAIT_OBJECT_0)
        return;
    LockCount++;
}

bool MutexImpl::TryLock()
{
    DWORD ret;
    if ((ret=::WaitForSingleObject(hMutexOrSemaphore, 0)) != WAIT_OBJECT_0)
        return 0;
    LockCount++;
    return 1;
}

void MutexImpl::Unlock(Mutex* pmutex)
{
    OVR_UNUSED(pmutex);

    unsigned lockCount;
    LockCount--;
    lockCount = LockCount;

    // Release mutex
    if ((Recursive ? ReleaseMutex(hMutexOrSemaphore) :
                     ReleaseSemaphore(hMutexOrSemaphore, 1, NULL))  != 0)
    {
        // This used to call Wait handlers if lockCount == 0.
    }
}

bool MutexImpl::IsLockedByAnotherThread(Mutex* pmutex)
{
    // There could be multiple interpretations of IsLocked with respect to current thread
    if (LockCount == 0)
        return 0;
    if (!TryLock())
        return 1;
    Unlock(pmutex);
    return 0;
}

/*
bool    MutexImpl::IsSignaled() const
{
    // An mutex is signaled if it is not locked ANYWHERE
    // Note that this is different from IsLockedByAnotherThread function,
    // that takes current thread into account
    return LockCount == 0;
}
*/


// *** Actual Mutex class implementation

Mutex::Mutex(bool recursive)
{    
    pImpl = new MutexImpl(recursive);
}
Mutex::~Mutex()
{
    delete pImpl;
}

// Lock and try lock
void Mutex::DoLock()
{
    pImpl->DoLock();
}
bool Mutex::TryLock()
{
    return pImpl->TryLock();
}
void Mutex::Unlock()
{
    pImpl->Unlock(this);
}
bool Mutex::IsLockedByAnotherThread()
{
    return pImpl->IsLockedByAnotherThread(this);
}

//-----------------------------------------------------------------------------------
// ***** Event

bool Event::Wait(unsigned delay)
{
    Mutex::Locker lock(&StateMutex);

    // Do the correct amount of waiting
    if (delay == OVR_WAIT_INFINITE)
    {
        while(!State)
            StateWaitCondition.Wait(&StateMutex);
    }
    else if (delay)
    {
        if (!State)
            StateWaitCondition.Wait(&StateMutex, delay);
    }

    bool state = State;
    // Take care of temporary 'pulsing' of a state
    if (Temporary)
    {
        Temporary   = false;
        State       = false;
    }
    return state;
}

void Event::updateState(bool newState, bool newTemp, bool mustNotify)
{
    Mutex::Locker lock(&StateMutex);
    State       = newState;
    Temporary   = newTemp;
    if (mustNotify)
        StateWaitCondition.NotifyAll();    
}


//-----------------------------------------------------------------------------------
// ***** Win32 Wait Condition Implementation

// Internal implementation class
class WaitConditionImpl : public NewOverrideBase
{   
    // Event pool entries for extra events
    struct EventPoolEntry  : public NewOverrideBase
    {
        HANDLE          hEvent;
        EventPoolEntry  *pNext;
        EventPoolEntry  *pPrev;
    };
    
    Lock                WaitQueueLoc;
    // Stores free events that can be used later
    EventPoolEntry  *   pFreeEventList;
    
    // A queue of waiting objects to be signaled    
    EventPoolEntry*     pQueueHead;
    EventPoolEntry*     pQueueTail;

    // Allocation functions for free events
    EventPoolEntry*     GetNewEvent();
    void                ReleaseEvent(EventPoolEntry* pevent);

    // Queue operations
    void                QueuePush(EventPoolEntry* pentry);
    EventPoolEntry*     QueuePop();
    void                QueueFindAndRemove(EventPoolEntry* pentry);

public:

    // Constructor/destructor
    WaitConditionImpl();
    ~WaitConditionImpl();

    // Release mutex and wait for condition. The mutex is re-acqured after the wait.
    bool    Wait(Mutex *pmutex, unsigned delay = OVR_WAIT_INFINITE);

    // Notify a condition, releasing at one object waiting
    void    Notify();
    // Notify a condition, releasing all objects waiting
    void    NotifyAll();
};



WaitConditionImpl::WaitConditionImpl()
{
    pFreeEventList  = 0;
    pQueueHead      =
    pQueueTail      = 0;
}

WaitConditionImpl::~WaitConditionImpl()
{
    // Free all the resources
    EventPoolEntry* p       = pFreeEventList;
    EventPoolEntry* pentry;

    while(p)
    {
        // Move to next
        pentry = p;
        p = p->pNext;
        // Delete old
        ::CloseHandle(pentry->hEvent);
        delete pentry;  
    }   
    // Shouldn't we also consider the queue?

    // To be safe
    pFreeEventList  = 0;
    pQueueHead      =
    pQueueTail      = 0;
}


// Allocation functions for free events
WaitConditionImpl::EventPoolEntry* WaitConditionImpl::GetNewEvent()
{
    EventPoolEntry* pentry;

    // If there are any free nodes, use them
    if (pFreeEventList)
    {
        pentry          = pFreeEventList;
        pFreeEventList  = pFreeEventList->pNext;        
    }
    else
    {
        // Allocate a new node
        pentry          = new EventPoolEntry;
        pentry->pNext   = 0;
        pentry->pPrev   = 0;
        // Non-signaled manual event
        pentry->hEvent  = ::CreateEvent(NULL, TRUE, 0, NULL);
    }
    
    return pentry;
}

void WaitConditionImpl::ReleaseEvent(EventPoolEntry* pevent)
{
    // Mark event as non-signaled
    ::ResetEvent(pevent->hEvent);
    // And add it to free pool
    pevent->pNext   = pFreeEventList;
    pevent->pPrev   = 0;
    pFreeEventList  = pevent;
}

// Queue operations
void WaitConditionImpl::QueuePush(EventPoolEntry* pentry)
{
    // Items already exist? Just add to tail
    if (pQueueTail)
    {
        pentry->pPrev       = pQueueTail;
        pQueueTail->pNext   = pentry;
        pentry->pNext       = 0;        
        pQueueTail          = pentry;       
    }
    else
    {
        // No items in queue
        pentry->pNext   = 
        pentry->pPrev   = 0;
        pQueueHead      =
        pQueueTail      = pentry;
    }
}

WaitConditionImpl::EventPoolEntry* WaitConditionImpl::QueuePop()
{
    EventPoolEntry* pentry = pQueueHead;

    // No items, null pointer
    if (pentry)
    {
        // More items after this one? just grab the first item
        if (pQueueHead->pNext)
        {       
            pQueueHead  = pentry->pNext;
            pQueueHead->pPrev = 0;      
        }
        else
        {
            // Last item left
            pQueueTail =
            pQueueHead = 0;
        }
    }   
    return pentry;
}

void WaitConditionImpl::QueueFindAndRemove(EventPoolEntry* pentry)
{
    // Do an exhaustive search looking for an entry
    EventPoolEntry* p = pQueueHead;

    while(p)
    {
        // Entry found? Remove.
        if (p == pentry)
        {
            
            // Remove the node form the list
            // Prev link
            if (pentry->pPrev)
                pentry->pPrev->pNext = pentry->pNext;
            else
                pQueueHead = pentry->pNext;
            // Next link
            if (pentry->pNext)
                pentry->pNext->pPrev = pentry->pPrev;
            else
                pQueueTail = pentry->pPrev;
            // Done
            return;
        }

        // Move to next item
        p = p->pNext;
    }
}
    

bool WaitConditionImpl::Wait(Mutex *pmutex, unsigned delay)
{
    bool            result = 0;
    unsigned        i;
    unsigned        lockCount = pmutex->pImpl->LockCount;
    EventPoolEntry* pentry;

    // Mutex must have been locked
    if (lockCount == 0)
        return 0;
    
    // Add an object to the wait queue
    WaitQueueLoc.DoLock();
    QueuePush(pentry = GetNewEvent());
    WaitQueueLoc.Unlock();

    // Finally, release a mutex or semaphore
    if (pmutex->pImpl->Recursive)
    {
        // Release the recursive mutex N times
        pmutex->pImpl->LockCount = 0;
        for(i=0; i<lockCount; i++)
            ::ReleaseMutex(pmutex->pImpl->hMutexOrSemaphore);
    }
    else
    {
        pmutex->pImpl->LockCount = 0;
        ::ReleaseSemaphore(pmutex->pImpl->hMutexOrSemaphore, 1, NULL);
    }

    // Note that there is a gap here between mutex.Unlock() and Wait(). However,
    // if notify() comes in at this point in the other thread it will set our
    // corresponding event so wait will just fall through, as expected.

    // Block and wait on the event
    DWORD waitResult = ::WaitForSingleObject(pentry->hEvent,
                            (delay == OVR_WAIT_INFINITE) ? INFINITE : delay);
    /*
repeat_wait:
    DWORD waitResult =

    ::MsgWaitForMultipleObjects(1, &pentry->hEvent, FALSE,
                                (delay == OVR_WAIT_INFINITE) ? INFINITE : delay,
                                QS_ALLINPUT);
    */

    WaitQueueLoc.DoLock();
    switch(waitResult)
    {
        case WAIT_ABANDONED:
        case WAIT_OBJECT_0: 
            result = 1;
            // Wait was successful, therefore the event entry should already be removed
            // So just add entry back to a free list
            ReleaseEvent(pentry);
            break;
            /*
        case WAIT_OBJECT_0 + 1:
            // Messages in WINDOWS queue
            {
                MSG msg;
                PeekMessage(&msg, NULL, 0U, 0U, PM_NOREMOVE);             
                WaitQueueLoc.Unlock();
                goto repeat_wait;
            }
            break; */
        default:
            // Timeout, our entry should still be in a queue
            QueueFindAndRemove(pentry);
            ReleaseEvent(pentry);
    }
    WaitQueueLoc.Unlock();

    // Re-aquire the mutex
    for(i=0; i<lockCount; i++)
        pmutex->DoLock(); 

    // Return the result
    return result;
}

// Notify a condition, releasing the least object in a queue
void WaitConditionImpl::Notify()
{
    Lock::Locker   lock(&WaitQueueLoc);
    
    // Pop last entry & signal it
    EventPoolEntry* pentry = QueuePop();    
    if (pentry)
        ::SetEvent(pentry->hEvent); 
}

// Notify a condition, releasing all objects waiting
void WaitConditionImpl::NotifyAll()
{
    Lock::Locker   lock(&WaitQueueLoc);

    // Pop and signal all events
    // NOTE : There is no need to release the events, it's the waiters job to do so 
    EventPoolEntry* pentry = QueuePop();
    while (pentry)
    {
        ::SetEvent(pentry->hEvent);
        pentry = QueuePop();
    }
}



// *** Actual implementation of WaitCondition

WaitCondition::WaitCondition()
{
    pImpl = new WaitConditionImpl;
}
WaitCondition::~WaitCondition()
{
    delete pImpl;
}
    
// Wait without a mutex
bool    WaitCondition::Wait(Mutex *pmutex, unsigned delay)
{
    return pImpl->Wait(pmutex, delay);
}
// Notification
void    WaitCondition::Notify()
{
    pImpl->Notify();
}
void    WaitCondition::NotifyAll()
{
    pImpl->NotifyAll();
}



//-----------------------------------------------------------------------------------
// ***** Thread Class

//  Per-thread variable
//  MA: Don't use TLS for now - portability issues with DLLs, etc.
/*
#if !defined(OVR_CC_MSVC) || (OVR_CC_MSVC < 1300)
__declspec(thread)  Thread*    pCurrentThread      = 0;
#else
#pragma data_seg(".tls$")
__declspec(thread)  Thread*    pCurrentThread      = 0;
#pragma data_seg(".rwdata")
#endif
*/

// *** Thread constructors.

Thread::Thread(size_t stackSize, int processor)
{    
    CreateParams params;
    params.stackSize = stackSize;
    params.processor = processor;
    Init(params);
}

Thread::Thread(Thread::ThreadFn threadFunction, void*  userHandle, size_t stackSize, 
                 int processor, Thread::ThreadState initialState)
{
    CreateParams params(threadFunction, userHandle, stackSize, processor, initialState);
    Init(params);
}

Thread::Thread(const CreateParams& params)
{
    Init(params);
}
void Thread::Init(const CreateParams& params)
{
    // Clear the variables    
    ThreadFlags     = 0;
    ThreadHandle    = 0;
    IdValue         = 0;
    ExitCode        = 0;
    SuspendCount    = 0;
    StackSize       = params.stackSize;
    Processor       = params.processor;
    Priority        = params.priority;

    // Clear Function pointers
    ThreadFunction  = params.threadFunction;
    UserHandle      = params.userHandle;
    if (params.initialState != NotRunning)
        Start(params.initialState);

}

Thread::~Thread()
{
    // Thread should not running while object is being destroyed,
    // this would indicate ref-counting issue.
    //OVR_ASSERT(IsRunning() == 0);
  
    // Clean up thread.    
    CleanupSystemThread();
    ThreadHandle = 0;
}


// *** Overridable User functions.

// Default Run implementation
int Thread::Run()
{
	if (!ThreadFunction)
		return 0;

	int ret = ThreadFunction(this, UserHandle);

	return ret;
}

void Thread::OnExit()
{   
}

// Finishes the thread and releases internal reference to it.
void Thread::FinishAndRelease()
{
    // Note: thread must be US.
    ThreadFlags &= (uint32_t)~(OVR_THREAD_STARTED);
    ThreadFlags |= OVR_THREAD_FINISHED;

    // Release our reference; this is equivalent to 'delete this'
    // from the point of view of our thread.
    Release();
}


// *** ThreadList - used to tack all created threads

class ThreadList : public NewOverrideBase
{
    //------------------------------------------------------------------------
    struct ThreadHashOp
    {
        size_t operator()(const Thread* ptr)
        {
            return (((size_t)ptr) >> 6) ^ (size_t)ptr;
        }
    };

    HashSet<Thread*, ThreadHashOp>  ThreadSet;
    Mutex                           ThreadMutex;
    WaitCondition                   ThreadsEmpty;
    // Track the root thread that created us.
    ThreadId                        RootThreadId;

    static ThreadList* volatile pRunningThreads;

    void addThread(Thread *pthread)
    {
         Mutex::Locker lock(&ThreadMutex);
         ThreadSet.Add(pthread);
    }

    void removeThread(Thread *pthread)
    {
        Mutex::Locker lock(&ThreadMutex);
        ThreadSet.Remove(pthread);
        if (ThreadSet.GetSize() == 0)
            ThreadsEmpty.Notify();
    }

    void finishAllThreads()
    {
        // Only original root thread can call this.
        OVR_ASSERT(GetCurrentThreadId() == RootThreadId);

        Mutex::Locker lock(&ThreadMutex);
        while (ThreadSet.GetSize() != 0)
            ThreadsEmpty.Wait(&ThreadMutex);
    }

public:

    ThreadList()
    {
        RootThreadId = GetCurrentThreadId();
    }
    ~ThreadList() { }


    static void AddRunningThread(Thread *pthread)
    {
        // Non-atomic creation ok since only the root thread
        if (!pRunningThreads)
        {
            pRunningThreads = new ThreadList;
            OVR_ASSERT(pRunningThreads);
        }
        pRunningThreads->addThread(pthread);
    }

    // NOTE: 'pthread' might be a dead pointer when this is
    // called so it should not be accessed; it is only used
    // for removal.
    static void RemoveRunningThread(Thread *pthread)
    {
        OVR_ASSERT(pRunningThreads);        
        pRunningThreads->removeThread(pthread);
    }

    static void FinishAllThreads()
    {
        // This is ok because only root thread can wait for other thread finish.
        if (pRunningThreads)
        {           
            pRunningThreads->finishAllThreads();
            delete pRunningThreads;
            pRunningThreads = 0;
        }        
    }
};

// By default, we have no thread list.
ThreadList* volatile ThreadList::pRunningThreads = 0;


// FinishAllThreads - exposed publicly in Thread.
void Thread::FinishAllThreads()
{
    ThreadList::FinishAllThreads();
}


// *** Run override

int Thread::PRun()
{
    // Suspend us on start, if requested
    if (ThreadFlags & OVR_THREAD_START_SUSPENDED)
    {
        Suspend();
        ThreadFlags &= (uint32_t)~OVR_THREAD_START_SUSPENDED;
    }

    // Call the virtual run function
    ExitCode = Run();    

    return ExitCode;
}



/* MA: Don't use TLS for now.

// Static function to return a pointer to the current thread
void    Thread::InitCurrentThread(Thread *pthread)
{
    pCurrentThread = pthread;
}

// Static function to return a pointer to the current thread
Thread*    Thread::GetThread()
{
    return pCurrentThread;
}
*/


// *** User overridables

bool    Thread::GetExitFlag() const
{
    return (ThreadFlags & OVR_THREAD_EXIT) != 0;
}       

void    Thread::SetExitFlag(bool exitFlag)
{
    // The below is atomic since ThreadFlags is AtomicInt.
    if (exitFlag)
        ThreadFlags |= OVR_THREAD_EXIT;
    else
        ThreadFlags &= (uint32_t) ~OVR_THREAD_EXIT;
}


// Determines whether the thread was running and is now finished
bool    Thread::IsFinished() const
{
    return (ThreadFlags & OVR_THREAD_FINISHED) != 0;
}
// Determines whether the thread is suspended
bool    Thread::IsSuspended() const
{   
    return SuspendCount > 0;
}
// Returns current thread state
Thread::ThreadState Thread::GetThreadState() const
{
    if (IsSuspended())
        return Suspended;
    if (ThreadFlags & OVR_THREAD_STARTED)
        return Running;
    return NotRunning;
}
// Join thread
bool Thread::Join(int maxWaitMs) const
{
    // If polling,
    if (maxWaitMs == 0)
    {
        // Just return if finished
        return IsFinished();
    }
    // If waiting forever,
    else if (maxWaitMs > 0)
    {
        // Try waiting once
        WaitForSingleObject(ThreadHandle, maxWaitMs);

        // Return if the wait succeeded
        return IsFinished();
    }

    // While not finished,
    while (!IsFinished())
    {
        // Wait for the thread handle to signal
        WaitForSingleObject(ThreadHandle, INFINITE);
    }

    return true;
}


// ***** Thread management
/* static */
int Thread::GetOSPriority(ThreadPriority p)
{
    switch(p)
    {
    // If the process is REALTIME_PRIORITY_CLASS then it could have priority values 3 through14 and -3 through -14.
    case Thread::CriticalPriority:      return THREAD_PRIORITY_TIME_CRITICAL;   //  15
    case Thread::HighestPriority:       return THREAD_PRIORITY_HIGHEST;         //   2
    case Thread::AboveNormalPriority:   return THREAD_PRIORITY_ABOVE_NORMAL;    //   1
    case Thread::NormalPriority:        return THREAD_PRIORITY_NORMAL;          //   0
    case Thread::BelowNormalPriority:   return THREAD_PRIORITY_BELOW_NORMAL;    //  -1
    case Thread::LowestPriority:        return THREAD_PRIORITY_LOWEST;          //  -2
    case Thread::IdlePriority:          return THREAD_PRIORITY_IDLE;            // -15
    }
    return THREAD_PRIORITY_NORMAL;
}

/* static */
Thread::ThreadPriority Thread::GetOVRPriority(int osPriority)
{
    // If the process is REALTIME_PRIORITY_CLASS then it could have priority values 3 through14 and -3 through -14.
    // As a result, it's possible for those cases that an unknown/invalid ThreadPriority enum be returned. However,
    // in practice we don't expect to be using such processes.

    // The ThreadPriority types aren't linearly distributed, so we need to check for some values explicitly.
    if(osPriority == THREAD_PRIORITY_TIME_CRITICAL)
        return Thread::CriticalPriority;
    if(osPriority == THREAD_PRIORITY_IDLE)
        return Thread::IdlePriority;
    return (ThreadPriority)(Thread::NormalPriority - osPriority);
}

Thread::ThreadPriority Thread::GetPriority()
{
    int osPriority = ::GetThreadPriority(ThreadHandle);

    if(osPriority != THREAD_PRIORITY_ERROR_RETURN)
    {
        return GetOVRPriority(osPriority);
    }

    return NormalPriority;
}

/* static */
Thread::ThreadPriority Thread::GetCurrentPriority()
{
    int osPriority = ::GetThreadPriority(::GetCurrentThread());

    if(osPriority != THREAD_PRIORITY_ERROR_RETURN)
    {
        return GetOVRPriority(osPriority);
    }

    return NormalPriority;
}

bool Thread::SetPriority(ThreadPriority p)
{
    BOOL ret = ::SetThreadPriority(ThreadHandle, Thread::GetOSPriority(p));
    return (ret != FALSE);
}

/* static */
bool Thread::SetCurrentPriority(ThreadPriority p)
{
    BOOL ret = ::SetThreadPriority(::GetCurrentThread(), Thread::GetOSPriority(p));
    return (ret != FALSE);
}



// The actual first function called on thread start
#if defined(OVR_OS_WIN32)
unsigned WINAPI Thread_Win32StartFn(void * phandle)
#else // Other Micorosft OSs...
DWORD WINAPI Thread_Win32StartFn(void *phandle)
#endif
{
    Thread *   pthread = (Thread*)phandle;
    if (pthread->Processor != -1)
    {
        DWORD_PTR ret = SetThreadAffinityMask(GetCurrentThread(), (DWORD)pthread->Processor);
        if (ret == 0)
            OVR_DEBUG_LOG(("Could not set hardware processor for the thread"));
    }
    BOOL ret = ::SetThreadPriority(GetCurrentThread(), Thread::GetOSPriority(pthread->Priority));
    if (ret == 0)
        OVR_DEBUG_LOG(("Could not set thread priority"));
    OVR_UNUSED(ret);

    // Ensure that ThreadId is assigned once thread is running, in case
    // beginthread hasn't filled it in yet.
    pthread->IdValue = (ThreadId)(intptr_t)::GetCurrentThreadId(); // should be: typedef intptr_t ThreadId;

    DWORD       result = pthread->PRun();
    // Signal the thread as done and release it atomically.
    pthread->FinishAndRelease();
    // At this point Thread object might be dead; however we can still pass
    // it to RemoveRunningThread since it is only used as a key there.    
    ThreadList::RemoveRunningThread(pthread);
    return (unsigned) result;
}

bool Thread::Start(ThreadState initialState)
{
    if (initialState == NotRunning)
        return 0;
    if (GetThreadState() != NotRunning)
    {
        OVR_DEBUG_LOG(("Thread::Start failed - thread %p already running", this));
        return 0;
    }

    // Free old thread handle before creating the new one
    CleanupSystemThread();

    // AddRef to us until the thread is finished.
    AddRef();
    ThreadList::AddRunningThread(this);
    
    ExitCode        = 0;
    SuspendCount    = 0;
    ThreadFlags     = (initialState == Running) ? 0 : OVR_THREAD_START_SUSPENDED;
#if defined(OVR_OS_WIN32)
    ThreadHandle = (HANDLE) _beginthreadex(0, (unsigned)StackSize,
                                           Thread_Win32StartFn, this, 0, (unsigned*)&IdValue);
#else // Other Micorosft OSs...
    DWORD TheThreadId;
    ThreadHandle = CreateThread(0, (unsigned)StackSize,
                                           Thread_Win32StartFn, this, 0, &TheThreadId);
    IdValue = (ThreadId)TheThreadId;
#endif

    // Failed? Fail the function
    if (ThreadHandle == 0)
    {
        ThreadFlags = 0;
        Release();
        ThreadList::RemoveRunningThread(this);
        return 0;
    }
    return 1;
}


// Suspend the thread until resumed
bool Thread::Suspend()
{
    // Can't suspend a thread that wasn't started
    if (!(ThreadFlags & OVR_THREAD_STARTED))
        return 0;

    if (::SuspendThread(ThreadHandle) != 0xFFFFFFFF)
    {        
        SuspendCount++;        
        return 1;
    }
    return 0;
}

// Resumes currently suspended thread
bool Thread::Resume()
{
    // Can't suspend a thread that wasn't started
    if (!(ThreadFlags & OVR_THREAD_STARTED))
        return 0;

    // Decrement count, and resume thread if it is 0
    int32_t oldCount = SuspendCount.ExchangeAdd_Acquire(-1);
    if (oldCount >= 1)
    {
        if (oldCount == 1)
        {
            if (::ResumeThread(ThreadHandle) != 0xFFFFFFFF)
            {
                return 1;
            }
        }
        else
        {
            return 1;
        }
    }   
    return 0;
}


// Quits with an exit code  
void Thread::Exit(int exitCode)
{
    // Can only exist the current thread.
    // MA: Don't use TLS for now.
    //if (GetThread() != this)
    //    return;

    // Call the virtual OnExit function.
    OnExit();   

    // Signal this thread object as done and release it's references.
    FinishAndRelease();
    ThreadList::RemoveRunningThread(this);

    // Call the exit function.
#if defined(OVR_OS_WIN32) // _endthreadex doesn't exist on other Microsoft OSs and instead we need to call ExitThread directly.
    _endthreadex((unsigned)exitCode);
#else
    ExitThread((unsigned)exitCode);
#endif
}


void Thread::CleanupSystemThread()
{
    if (ThreadHandle != 0)
    {
        ::CloseHandle(ThreadHandle);
        ThreadHandle = 0;
    }
}

// *** Sleep functions
// static
bool Thread::Sleep(unsigned secs)
{
    ::Sleep(secs*1000);
    return 1;
}

// static
bool Thread::MSleep(unsigned msecs)
{
    ::Sleep(msecs);
    return 1;
}



void Thread::SetThreadName( const char* name )
{
    if(IdValue)
        SetThreadName(name, IdValue);
    // Else we don't know what thread to name. We can save the name and wait until the thread is created.
}


void Thread::SetThreadName(const char* name, ThreadId threadId)
{
    // MinGW does not support SEH exceptions, hence CPP: && defined(OVR_CC_MSVC)
    #if ( !defined(OVR_BUILD_SHIPPING) || defined(OVR_BUILD_PROFILING) ) && defined(OVR_CC_MSVC)
        // http://msdn.microsoft.com/en-us/library/xcb2z8hs.aspx
        #pragma pack(push,8)
        struct THREADNAME_INFO {
            DWORD  dwType;     // Must be 0x1000
            LPCSTR szName;     // Pointer to name (in user address space)
            DWORD  dwThreadID; // Thread ID (-1 for caller thread)
            DWORD  dwFlags;    // Reserved for future use; must be zero
        };
        #pragma pack(pop)

        THREADNAME_INFO info = { 0x1000, name, (DWORD)threadId, 0 };

        __try
        {
            RaiseException( 0x406D1388, 0, sizeof(info)/sizeof(ULONG_PTR), reinterpret_cast<ULONG_PTR*>(&info));
        }
        __except( GetExceptionCode()==0x406D1388 ? EXCEPTION_CONTINUE_EXECUTION : EXCEPTION_EXECUTE_HANDLER )
        {
            return;
        }
    #endif // OVR_BUILD_SHIPPING
}


void Thread::SetCurrentThreadName( const char* name )
{
    SetThreadName(name, (ThreadId)::GetCurrentThreadId());
}


void Thread::GetThreadName(char* name, size_t /*nameCapacity*/, ThreadId /*threadId*/)
{
    // Not possible on Windows.
    name[0] = 0;
}


void Thread::GetCurrentThreadName(char* name, size_t /*nameCapacity*/)
{
    // Not possible on Windows.
    name[0] = 0;
}


// static
int  Thread::GetCPUCount()
{
    SYSTEM_INFO sysInfo;

    #if defined(_WIN32_WINNT) && (_WIN32_WINNT >= 0x0501) // GetNativeSystemInfo requires WinXP+ and a corresponding SDK (0x0501) or later.
        GetNativeSystemInfo(&sysInfo);
    #else
        GetSystemInfo(&sysInfo);
    #endif

    return (int) sysInfo.dwNumberOfProcessors;
}

// Returns the unique Id of a thread it is called on, intended for
// comparison purposes.
ThreadId GetCurrentThreadId()
{
    return (ThreadId)(intptr_t)::GetCurrentThreadId(); // should be: typedef intptr_t ThreadId;
}

} // OVR

#endif