nuclear@0: /************************************************************************************
nuclear@0: 
nuclear@0: Filename    :   OVR_Atomic.cpp
nuclear@0: Content     :   Contains atomic operations and inline fastest locking
nuclear@0:                 functionality. Will contain #ifdefs for OS efficiency.
nuclear@0:                 Have non-thread-safe implementation if not available.
nuclear@0: Created     :   September 19, 2012
nuclear@0: Notes       : 
nuclear@0: 
nuclear@0: Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.
nuclear@0: 
nuclear@0: Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License"); 
nuclear@0: you may not use the Oculus VR Rift SDK except in compliance with the License, 
nuclear@0: which is provided at the time of installation or download, or which 
nuclear@0: otherwise accompanies this software in either electronic or hard copy form.
nuclear@0: 
nuclear@0: You may obtain a copy of the License at
nuclear@0: 
nuclear@0: http://www.oculusvr.com/licenses/LICENSE-3.2 
nuclear@0: 
nuclear@0: Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
nuclear@0: distributed under the License is distributed on an "AS IS" BASIS,
nuclear@0: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
nuclear@0: See the License for the specific language governing permissions and
nuclear@0: limitations under the License.
nuclear@0: 
nuclear@0: ************************************************************************************/
nuclear@0: 
nuclear@0: #include "OVR_Atomic.h"
nuclear@0: #include "OVR_Allocator.h"
nuclear@0: 
nuclear@0: #ifdef OVR_ENABLE_THREADS
nuclear@0: 
nuclear@0: // Include Windows 8-Metro compatible Synchronization API
nuclear@0: #if defined(OVR_OS_MS) && defined(NTDDI_WIN8) && (NTDDI_VERSION >= NTDDI_WIN8)
nuclear@0: #include <synchapi.h>
nuclear@0: #endif
nuclear@0: 
nuclear@0: 
nuclear@0: namespace OVR {
nuclear@0: 
nuclear@0: // ***** Windows Lock implementation
nuclear@0: 
nuclear@0: #if defined(OVR_OS_MS)
nuclear@0: 
nuclear@0: // ***** Standard Win32 Lock implementation
nuclear@0: 
nuclear@0: // Constructors
nuclear@0: Lock::Lock(unsigned spinCount)
nuclear@0: {
nuclear@0:     #if defined(NTDDI_WIN8) && (NTDDI_VERSION >= NTDDI_WIN8)
nuclear@0:        // On Windows 8 we use InitializeCriticalSectionEx due to Metro-Compatibility
nuclear@0:        InitializeCriticalSectionEx(&cs, (DWORD)spinCount,
nuclear@0:                                    OVR_DEBUG_SELECT(NULL, CRITICAL_SECTION_NO_DEBUG_INFO));
nuclear@0:     #else
nuclear@0:         ::InitializeCriticalSectionAndSpinCount(&cs, (DWORD)spinCount); // This is available with WindowsXP+.
nuclear@0:     #endif
nuclear@0: }
nuclear@0: 
nuclear@0: 
nuclear@0: Lock::~Lock()
nuclear@0: {
nuclear@0:     DeleteCriticalSection(&cs);
nuclear@0: }
nuclear@0: 
nuclear@0: 
nuclear@0: #endif
nuclear@0: 
nuclear@0: 
nuclear@0: //-------------------------------------------------------------------------------------
nuclear@0: // ***** SharedLock
nuclear@0: 
nuclear@0: // This is a general purpose globally shared Lock implementation that should probably be
nuclear@0: // moved to Kernel.
nuclear@0: // May in theory busy spin-wait if we hit contention on first lock creation,
nuclear@0: // but this shouldn't matter in practice since Lock* should be cached.
nuclear@0: 
nuclear@0: 
nuclear@0: enum { LockInitMarker = 0xFFFFFFFF };
nuclear@0: 
nuclear@0: Lock* SharedLock::GetLockAddRef()
nuclear@0: {
nuclear@0:     int oldUseCount;
nuclear@0: 
nuclear@0:     do {
nuclear@0:         oldUseCount = UseCount;
nuclear@0:         if (oldUseCount == (int)LockInitMarker)
nuclear@0:             continue;
nuclear@0: 
nuclear@0:         if (oldUseCount == 0)
nuclear@0:         {
nuclear@0:             // Initialize marker
nuclear@0:             if (AtomicOps<int>::CompareAndSet_Sync(&UseCount, 0, LockInitMarker))
nuclear@0:             {
nuclear@0:                 Construct<Lock>(Buffer);
nuclear@0:                 do { }
nuclear@0:                 while (!AtomicOps<int>::CompareAndSet_Sync(&UseCount, LockInitMarker, 1));
nuclear@0:                 return toLock();
nuclear@0:             }
nuclear@0:             continue;
nuclear@0:         }
nuclear@0: 
nuclear@0:     } while (!AtomicOps<int>::CompareAndSet_NoSync(&UseCount, oldUseCount, oldUseCount + 1));
nuclear@0: 
nuclear@0:     return toLock();
nuclear@0: }
nuclear@0: 
nuclear@0: void SharedLock::ReleaseLock(Lock* plock)
nuclear@0: {
nuclear@0:     OVR_UNUSED(plock);
nuclear@0:     OVR_ASSERT(plock == toLock());
nuclear@0: 
nuclear@0:     int oldUseCount;
nuclear@0: 
nuclear@0:     do {
nuclear@0:         oldUseCount = UseCount;
nuclear@0:         OVR_ASSERT(oldUseCount != (int)LockInitMarker);
nuclear@0: 
nuclear@0:         if (oldUseCount == 1)
nuclear@0:         {
nuclear@0:             // Initialize marker
nuclear@0:             if (AtomicOps<int>::CompareAndSet_Sync(&UseCount, 1, LockInitMarker))
nuclear@0:             {
nuclear@0:                 Destruct<Lock>(toLock());
nuclear@0: 
nuclear@0:                 do { }
nuclear@0:                 while (!AtomicOps<int>::CompareAndSet_Sync(&UseCount, LockInitMarker, 0));
nuclear@0: 
nuclear@0:                 return;
nuclear@0:             }
nuclear@0:             continue;
nuclear@0:         }
nuclear@0: 
nuclear@0:     } while (!AtomicOps<int>::CompareAndSet_NoSync(&UseCount, oldUseCount, oldUseCount - 1));
nuclear@0: }
nuclear@0: 
nuclear@0: } // OVR
nuclear@0: 
nuclear@0: #endif // OVR_ENABLE_THREADS