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Chaves

 
class Key {  
   boolean locked; 
   Queue waiting; 
}  
 
void lock(Key k) {  
   InterruptStatus is = saveInterruptStatus();
   disableInterrupts(); 
   if(k.locked) {  
      k.waiting.put(currentProcess); 
      currentProcess.state = WAITING; 
      transfer(currentProcess.coroutine, kernel); 
   }  
   k.locked = true; 
   is.restore(); 
   /* lock pode ser chamada por processos com interrupcoes 
      inibidas ou nao, e por isto o status \'{e} restabelecido 
   */ 
}  
 
void unlock(Key k) {   
   InterruptStatus is = saveInterruptStatus();
   disableInterrupts(); 
   if(k.waiting.empty()) {   
      k.locked = false;  
   }  else {   
      Process p = k.waiting.get(); 
      p.state = READY; 
      ready.put(p); 
   }  
   is.restore(); 
}