Fixed compile errors, added Semaphore code

[tpg/acess2.git] / Kernel / threads.c

diff --git a/Kernel/threads.c b/Kernel/threads.c
index 73c3f3c..8700154 100644 (file)
--- a/Kernel/threads.c
+++ b/Kernel/threads.c
@@ -62,6 +62,7 @@ tGID  Threads_GetGID(void);
  int   Threads_SetGID(Uint *Errno, tUID ID);
 void   Threads_Dump(void);
 void   Threads_DumpActive(void);
+
 void   Mutex_Acquire(tMutex *Mutex);
 void   Mutex_Release(tMutex *Mutex);
  int   Mutex_IsLocked(tMutex *Mutex);
@@ -1227,6 +1228,86 @@ int Mutex_IsLocked(tMutex *Mutex)
        return Mutex->Owner != NULL;
 }
 
+/**
+ * \brief Initialise the semaphore
+ * \param Value        Initial value of the semaphore
+ * \param Label        Symbolic name
+ */
+void Semaphore_Init(tSemaphore *Sem, int Value, const char *Label)
+{
+       Sem->Value = Value;
+       Sem->Name = Label;
+}
+
+/**
+ * \brief Acquire a "item" from the semaphore
+ */
+void Semaphore_Wait(tSemaphore *Sem)
+{
+       tThread *us;
+       
+       SHORTLOCK( &Sem->Protector );
+       if( Sem->Value > 0 ) {
+               Sem->Value --;
+               SHORTREL( &Sem->Protector );
+               return ;
+       }
+       
+       SHORTLOCK( &glThreadListLock );
+       
+       // - Remove from active list
+       us = Threads_RemActive();
+       us->Next = NULL;
+       // - Mark as sleeping
+       us->Status = THREAD_STAT_SEMAPHORESLEEP;
+       us->WaitPointer = Sem;
+       
+       // - Add to waiting
+       if(Sem->LastWaiting) {
+               Sem->LastWaiting->Next = us;
+               Sem->LastWaiting = us;
+       }
+       else {
+               Sem->Waiting = us;
+               Sem->LastWaiting = us;
+       }
+       
+       SHORTREL( &glThreadListLock );
+       SHORTREL( &Sem->Protector );
+       while(us->Status == THREAD_STAT_MUTEXSLEEP)     Threads_Yield();
+       // We're only woken when there's something avaliable
+       us->WaitPointer = NULL;
+}
+
+/**
+ * \brief Add an "item" to the semaphore
+ */
+void Semaphore_Signal(tSemaphore *Sem)
+{
+       SHORTLOCK( &Sem->Protector );
+       Sem->Value ++;
+       
+       if( Sem->Waiting )
+       {
+               tThread *toWake = Sem->Waiting;
+               
+               Sem->Waiting = Sem->Waiting->Next;      // Next!
+               // Reset ->LastWaiting to NULL if we have just removed the last waiting thread
+               if( Sem->Waiting == NULL )
+                       Sem->LastWaiting = NULL;
+               
+               // Wake new owner
+               SHORTLOCK( &glThreadListLock );
+               if( toWake->Status != THREAD_STAT_ACTIVE )
+                       Threads_AddActive(toWake);
+               SHORTREL( &glThreadListLock );
+               
+               // Decrement (the value is now "owned" by `toWake`)
+               Sem->Value --;
+       }
+       SHORTREL( &Sem->Protector );
+}
+
 // === EXPORTS ===
 EXPORT(Threads_GetUID);
 EXPORT(Threads_GetGID);