source/lib/module_init.cpp

   1 /* Copyright (C) 2010 Wildfire Games.
   2  *
   3  * Permission is hereby granted, free of charge, to any person obtaining
   4  * a copy of this software and associated documentation files (the
   5  * "Software"), to deal in the Software without restriction, including
   6  * without limitation the rights to use, copy, modify, merge, publish,
   7  * distribute, sublicense, and/or sell copies of the Software, and to
   8  * permit persons to whom the Software is furnished to do so, subject to
   9  * the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included
  12  * in all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  15  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  16  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  17  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  18  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  19  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  20  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 /*
  24  * helpers for module initialization/shutdown.
  25  */
  26
  27 #include "precompiled.h"
  28 #include "lib/module_init.h"
  29
  30 #include "lib/sysdep/cpu.h"     // cpu_CAS
  31
  32 // not yet initialized, or already shutdown
  33 static const ModuleInitState UNINITIALIZED = 0; // value documented in header
  34 // running user callback - concurrent ModuleInit callers must spin
  35 static const ModuleInitState BUSY = ERR::AGAIN; // never returned
  36 // init succeeded; allow shutdown
  37 static const ModuleInitState INITIALIZED = INFO::SKIPPED;
  38
  39
  40 Status ModuleInit(volatile ModuleInitState* initState, Status (*init)())
  41 {
  42         for(;;)
  43         {
  44                 if(cpu_CAS(initState, UNINITIALIZED, BUSY))
  45                 {
  46                         Status ret = init();
  47                         *initState = (ret == INFO::OK)? INITIALIZED : ret;
  48                         COMPILER_FENCE;
  49                         return ret;
  50                 }
  51
  52                 const ModuleInitState latchedInitState = *initState;
  53                 if(latchedInitState == UNINITIALIZED || latchedInitState == BUSY)
  54                 {
  55                         cpu_Pause();
  56                         continue;
  57                 }
  58
  59                 ENSURE(latchedInitState == INITIALIZED || latchedInitState < 0);
  60                 return (Status)latchedInitState;
  61         }
  62 }
  63
  64
  65 Status ModuleShutdown(volatile ModuleInitState* initState, void (*shutdown)())
  66 {
  67         for(;;)
  68         {
  69                 if(cpu_CAS(initState, INITIALIZED, BUSY))
  70                 {
  71                         shutdown();
  72                         *initState = UNINITIALIZED;
  73                         COMPILER_FENCE;
  74                         return INFO::OK;
  75                 }
  76
  77                 const ModuleInitState latchedInitState = *initState;
  78                 if(latchedInitState == INITIALIZED || latchedInitState == BUSY)
  79                 {
  80                         cpu_Pause();
  81                         continue;
  82                 }
  83
  84                 if(latchedInitState == UNINITIALIZED)
  85                         return INFO::SKIPPED;
  86
  87                 ENSURE(latchedInitState < 0);
  88                 return (Status)latchedInitState;
  89         }
  90 }