schedule.cc

   1 #include "threads.h"
   2 #include "schedule.h"
   3 #include "common.h"
   4 #include "model.h"
   5
   6 /** Constructor */
   7 Scheduler::Scheduler() :
   8         is_enabled(NULL),
   9         enabled_len(0),
  10         curr_thread_index(0),
  11         current(NULL)
  12 {
  13 }
  14
  15 void Scheduler::set_enabled(Thread *t, bool enabled_status) {
  16         int threadid=id_to_int(t->get_id());
  17         if (threadid>=enabled_len) {
  18                 bool * new_enabled=(bool *)malloc(sizeof(bool)*(threadid+1));
  19                 memcpy(new_enabled, is_enabled, enabled_len*sizeof(bool));
  20                 memset(&new_enabled[enabled_len], 0, (threadid+1-enabled_len)*sizeof(bool));
  21                 free(is_enabled);
  22                 is_enabled=new_enabled;
  23                 enabled_len=threadid+1;
  24         }
  25         is_enabled[threadid]=enabled_status;
  26 }
  27
  28 /**
  29  * Add a Thread to the scheduler's ready list.
  30  * @param t The Thread to add
  31  */
  32 void Scheduler::add_thread(Thread *t)
  33 {
  34         DEBUG("thread %d\n", t->get_id());
  35         set_enabled(t, true);
  36 }
  37
  38 /**
  39  * Remove a given Thread from the scheduler.
  40  * @param t The Thread to remove
  41  */
  42 void Scheduler::remove_thread(Thread *t)
  43 {
  44         if (current == t)
  45                 current = NULL;
  46         set_enabled(t, false);
  47 }
  48
  49 /**
  50  * Prevent a Thread from being scheduled. The sleeping Thread should be
  51  * re-awoken via Scheduler::wake.
  52  * @param thread The Thread that should sleep
  53  */
  54 void Scheduler::sleep(Thread *t)
  55 {
  56         set_enabled(t, false);
  57         t->set_state(THREAD_BLOCKED);
  58 }
  59
  60 /**
  61  * Wake a Thread up that was previously waiting (see Scheduler::wait)
  62  * @param t The Thread to wake up
  63  */
  64 void Scheduler::wake(Thread *t)
  65 {
  66         set_enabled(t, true);
  67         t->set_state(THREAD_READY);
  68 }
  69
  70 /**
  71  * Remove one Thread from the scheduler. This implementation defaults to FIFO,
  72  * if a thread is not already provided.
  73  *
  74  * @param t Thread to run, if chosen by an external entity (e.g.,
  75  * ModelChecker). May be NULL to indicate no external choice.
  76  * @return The next Thread to run
  77  */
  78 Thread * Scheduler::next_thread(Thread *t)
  79 {
  80         if ( t == NULL ) {
  81                 int old_curr_thread = curr_thread_index;
  82                 while(true) {
  83                         curr_thread_index = (curr_thread_index+1) % enabled_len;
  84                         if (is_enabled[curr_thread_index]) {
  85                                 t = model->get_thread(int_to_id(curr_thread_index));
  86                                 break;
  87                         }
  88                         if (curr_thread_index == old_curr_thread) {
  89                                 print();
  90                                 return NULL;
  91                         }
  92                 }
  93         } else {
  94                 curr_thread_index = id_to_int(t->get_id());
  95         }
  96
  97         current = t;
  98         print();
  99         return t;
 100 }
 101
 102 /**
 103  * @return The currently-running Thread
 104  */
 105 Thread * Scheduler::get_current_thread() const
 106 {
 107         return current;
 108 }
 109
 110 /**
 111  * Print debugging information about the current state of the scheduler. Only
 112  * prints something if debugging is enabled.
 113  */
 114 void Scheduler::print() const
 115 {
 116         if (current)
 117                 DEBUG("Current thread: %d\n", current->get_id());
 118         else
 119                 DEBUG("No current thread\n");
 120 }