KernelLand/Kernel/semaphore.c

   1 /*
   2  * Acess2 Kernel
   3  * - By John Hodge (thePowersGang)
   4  *
   5  * semaphore.c
   6  * - Semaphores
   7  */
   8 #include <acess.h>
   9 #include <semaphore.h>
  10 #include <threads_int.h>
  11
  12 #define SEMAPHORE_DEBUG         0       // Debug semaphores
  13
  14 // === CODE ===
  15 //
  16 // Initialise a semaphore
  17 //
  18 void Semaphore_Init(tSemaphore *Sem, int Value, int MaxValue, const char *Module, const char *Name)
  19 {
  20         memset(Sem, 0, sizeof(tSemaphore));
  21         Sem->Value = Value;
  22         Sem->ModName = Module;
  23         Sem->Name = Name;
  24         Sem->MaxValue = MaxValue;
  25 }
  26 //
  27 // Wait for items to be avaliable
  28 //
  29 int Semaphore_Wait(tSemaphore *Sem, int MaxToTake)
  30 {
  31         tThread *us;
  32          int    taken;
  33         if( MaxToTake < 0 ) {
  34                 Log_Warning("Threads", "Semaphore_Wait: User bug - MaxToTake(%i) < 0, Sem=%p(%s)",
  35                         MaxToTake, Sem, Sem->Name);
  36                 MaxToTake = 0;
  37         }
  38
  39         SHORTLOCK( &Sem->Protector );
  40
  41         // Check if there's already items avaliable
  42         if( Sem->Value > 0 )
  43         {
  44                 // Take what we need
  45                 if( MaxToTake && Sem->Value > MaxToTake )
  46                         taken = MaxToTake;
  47                 else
  48                         taken = Sem->Value;
  49                 Sem->Value -= taken;
  50         }
  51         else
  52         {
  53                 SHORTLOCK( &glThreadListLock );
  54
  55                 // - Remove from active list
  56                 us = Threads_RemActive();
  57                 us->Next = NULL;
  58                 // - Mark as sleeping
  59                 us->Status = THREAD_STAT_SEMAPHORESLEEP;
  60                 us->WaitPointer = Sem;
  61                 us->RetStatus = MaxToTake;      // Use RetStatus as a temp variable
  62
  63                 // - Add to waiting
  64                 if(Sem->LastWaiting) {
  65                         Sem->LastWaiting->Next = us;
  66                         Sem->LastWaiting = us;
  67                 }
  68                 else {
  69                         Sem->Waiting = us;
  70                         Sem->LastWaiting = us;
  71                 }
  72
  73                 #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
  74                 Log("%p (%i %s) waiting on semaphore %p %s:%s",
  75                         us, us->TID, us->ThreadName,
  76                         Sem, Sem->ModName, Sem->Name);
  77                 #endif
  78
  79                 SHORTREL( &Sem->Protector );    // Release first to make sure it is released
  80                 SHORTREL( &glThreadListLock );
  81                 while( us->Status == THREAD_STAT_SEMAPHORESLEEP )
  82                 {
  83                         Threads_Yield();
  84                         if(us->Status == THREAD_STAT_SEMAPHORESLEEP)
  85                                 Log_Warning("Threads", "Semaphore %p %s:%s re-schedulued while asleep",
  86                                         Sem, Sem->ModName, Sem->Name);
  87                 }
  88                 #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
  89                 Log("Semaphore %p %s:%s woken", Sem, Sem->ModName, Sem->Name);
  90                 #endif
  91                 // We're only woken when there's something avaliable (or a signal arrives)
  92                 us->WaitPointer = NULL;
  93
  94                 taken = us->RetStatus;
  95
  96                 // Get the lock again
  97                 SHORTLOCK( &Sem->Protector );
  98         }
  99
 100         // While there is space, and there are thread waiting
 101         // wake the first thread and give it what it wants (or what's left)
 102         while( (Sem->MaxValue == 0 || Sem->Value < Sem->MaxValue) && Sem->Signaling )
 103         {
 104                  int    given;
 105                 tThread *toWake = Sem->Signaling;
 106
 107                 Sem->Signaling = Sem->Signaling->Next;
 108                 // Reset ->LastWaiting to NULL if we have just removed the last waiting thread
 109                 if( Sem->Signaling == NULL )
 110                         Sem->LastSignaling = NULL;
 111
 112                 // Figure out how much to give
 113                 if( toWake->RetStatus && Sem->Value + toWake->RetStatus < Sem->MaxValue )
 114                         given = toWake->RetStatus;
 115                 else
 116                         given = Sem->MaxValue - Sem->Value;
 117                 Sem->Value -= given;
 118
 119
 120                 #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
 121                 Log("%p (%i %s) woken by wait on %p %s:%s",
 122                         toWake, toWake->TID, toWake->ThreadName,
 123                         Sem, Sem->ModName, Sem->Name);
 124                 #endif
 125
 126                 // Save the number we gave to the thread's status
 127                 toWake->RetStatus = given;
 128
 129                 // Wake the sleeper
 130                 if( toWake->Status != THREAD_STAT_ACTIVE )
 131                         Threads_AddActive(toWake);
 132         }
 133         SHORTREL( &Sem->Protector );
 134
 135         #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
 136         Log("Semaphore %p %s:%s took %i by wait",
 137                 Sem, Sem->ModName, Sem->Name, taken);
 138         #endif
 139
 140         return taken;
 141 }
 142
 143 //
 144 // Add items to a semaphore
 145 //
 146 int Semaphore_Signal(tSemaphore *Sem, int AmmountToAdd)
 147 {
 148          int    given;
 149          int    added;
 150
 151         if( AmmountToAdd < 0 ) {
 152                 Log_Warning("Threads", "Semaphore_Signal: User bug - AmmountToAdd(%i) < 0, Sem=%p(%s)",
 153                         AmmountToAdd, Sem, Sem->Name);
 154         }
 155         SHORTLOCK( &Sem->Protector );
 156
 157         // Check if we have to block
 158         if( Sem->MaxValue && Sem->Value == Sem->MaxValue )
 159         {
 160                 tThread *us;
 161                 #if 0
 162                 Log_Debug("Threads", "Semaphore_Signal: IDLE Sem = %s:%s", Sem->ModName, Sem->Name);
 163                 Log_Debug("Threads", "Semaphore_Signal: Sem->Value(%i) == Sem->MaxValue(%i)", Sem->Value, Sem->MaxValue);
 164                 #endif
 165
 166                 SHORTLOCK( &glThreadListLock );
 167                 // - Remove from active list
 168                 us = Threads_RemActive();
 169                 us->Next = NULL;
 170                 // - Mark as sleeping
 171                 us->Status = THREAD_STAT_SEMAPHORESLEEP;
 172                 us->WaitPointer = Sem;
 173                 us->RetStatus = AmmountToAdd;   // Use RetStatus as a temp variable
 174
 175                 // - Add to waiting
 176                 if(Sem->LastSignaling) {
 177                         Sem->LastSignaling->Next = us;
 178                         Sem->LastSignaling = us;
 179                 }
 180                 else {
 181                         Sem->Signaling = us;
 182                         Sem->LastSignaling = us;
 183                 }
 184
 185                 #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
 186                 Log("%p (%i %s) signaling semaphore %p %s:%s",
 187                         us, us->TID, us->ThreadName,
 188                         Sem, Sem->ModName, Sem->Name);
 189                 #endif
 190
 191                 SHORTREL( &glThreadListLock );
 192                 SHORTREL( &Sem->Protector );
 193                 while(us->Status == THREAD_STAT_SEMAPHORESLEEP) Threads_Yield();
 194                 // We're only woken when there's something avaliable
 195                 us->WaitPointer = NULL;
 196
 197                 added = us->RetStatus;
 198
 199                 // Get the lock again
 200                 SHORTLOCK( &Sem->Protector );
 201         }
 202         // Non blocking
 203         else
 204         {
 205                 // Figure out how much we need to take off
 206                 if( Sem->MaxValue && Sem->Value + AmmountToAdd > Sem->MaxValue)
 207                         added = Sem->MaxValue - Sem->Value;
 208                 else
 209                         added = AmmountToAdd;
 210                 Sem->Value += added;
 211         }
 212
 213         // While there are items avaliable, and there are thread waiting
 214         // wake the first thread and give it what it wants (or what's left)
 215         while( Sem->Value && Sem->Waiting )
 216         {
 217                 tThread *toWake = Sem->Waiting;
 218
 219                 // Remove thread from list (double ended, so clear LastWaiting if needed)
 220                 Sem->Waiting = Sem->Waiting->Next;
 221                 if( Sem->Waiting == NULL )
 222                         Sem->LastWaiting = NULL;
 223
 224                 // Figure out how much to give to woken thread
 225                 // - Requested count is stored in ->RetStatus
 226                 if( toWake->RetStatus && Sem->Value > toWake->RetStatus )
 227                         given = toWake->RetStatus;
 228                 else
 229                         given = Sem->Value;
 230                 Sem->Value -= given;
 231
 232                 // Save the number we gave to the thread's status
 233                 toWake->RetStatus = given;
 234
 235                 if(toWake->bInstrTrace)
 236                         Log("%s(%i) given %i from %p", toWake->ThreadName, toWake->TID, given, Sem);
 237                 #if DEBUG_TRACE_STATE || SEMAPHORE_DEBUG
 238                 Log("%p (%i %s) woken by signal on %p %s:%s",
 239                         toWake, toWake->TID, toWake->ThreadName,
 240                         Sem, Sem->ModName, Sem->Name);
 241                 #endif
 242
 243                 // Wake the sleeper
 244                 if( toWake->Status != THREAD_STAT_ACTIVE )
 245                         Threads_AddActive(toWake);
 246                 else
 247                         Warning("Thread %p (%i %s) is already awake", toWake, toWake->TID, toWake->ThreadName);
 248         }
 249         SHORTREL( &Sem->Protector );
 250
 251         return added;
 252 }
 253
 254 //
 255 // Get the current value of a semaphore
 256 //
 257 int Semaphore_GetValue(tSemaphore *Sem)
 258 {
 259         return Sem->Value;
 260 }
 261
 262 // === EXPORTS ===
 263 EXPORT(Semaphore_Init);
 264 EXPORT(Semaphore_Wait);
 265 EXPORT(Semaphore_Signal);