framework/delibs/dethread/deSingleton.c

   1 /*-------------------------------------------------------------------------
   2  * drawElements Thread Library
   3  * ---------------------------
   4  *
   5  * Copyright 2014 The Android Open Source Project
   6  *
   7  * Licensed under the Apache License, Version 2.0 (the "License");
   8  * you may not use this file except in compliance with the License.
   9  * You may obtain a copy of the License at
  10  *
  11  *      http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software
  14  * distributed under the License is distributed on an "AS IS" BASIS,
  15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  * See the License for the specific language governing permissions and
  17  * limitations under the License.
  18  *
  19  *//*!
  20  * \file
  21  * \brief Thread-safe singleton.
  22  *//*--------------------------------------------------------------------*/
  23
  24 #include "deSingleton.h"
  25 #include "deAtomic.h"
  26 #include "deThread.h"
  27
  28 DE_STATIC_ASSERT(sizeof(deSingletonState) == sizeof(deUint32));
  29
  30 void deInitSingleton (volatile deSingletonState* singletonState, deSingletonConstructorFunc constructor, void* arg)
  31 {
  32         if (*singletonState != DE_SINGLETON_STATE_INITIALIZED)
  33         {
  34                 deSingletonState curState = (deSingletonState)deAtomicCompareExchange32((volatile deUint32*)singletonState, (deUint32)DE_SINGLETON_STATE_NOT_INITIALIZED, (deUint32)DE_SINGLETON_STATE_INITIALIZING);
  35
  36                 if (curState == DE_SINGLETON_STATE_NOT_INITIALIZED)
  37                 {
  38                         constructor(arg);
  39
  40                         deMemoryReadWriteFence();
  41
  42                         *singletonState = DE_SINGLETON_STATE_INITIALIZED;
  43
  44                         deMemoryReadWriteFence();
  45                 }
  46                 else if (curState == DE_SINGLETON_STATE_INITIALIZING)
  47                 {
  48                         for (;;)
  49                         {
  50                                 deMemoryReadWriteFence();
  51
  52                                 if (*singletonState == DE_SINGLETON_STATE_INITIALIZED)
  53                                         break;
  54                                 else
  55                                         deYield();
  56                         }
  57                 }
  58
  59                 DE_ASSERT(*singletonState == DE_SINGLETON_STATE_INITIALIZED);
  60         }
  61 }