schedule.cc

   1 #include <string.h>
   2 #include <stdlib.h>
   3
   4 #include "threads.h"
   5 #include "schedule.h"
   6 #include "common.h"
   7 #include "model.h"
   8
   9 /** Constructor */
  10 Scheduler::Scheduler() :
  11         is_enabled(NULL),
  12         enabled_len(0),
  13         curr_thread_index(0),
  14         current(NULL)
  15 {
  16 }
  17
  18 void Scheduler::set_enabled(Thread *t, bool enabled_status) {
  19         int threadid=id_to_int(t->get_id());
  20         if (threadid>=enabled_len) {
  21                 bool * new_enabled=(bool *)malloc(sizeof(bool)*(threadid+1));
  22                 memset(&new_enabled[enabled_len], 0, (threadid+1-enabled_len)*sizeof(bool));
  23                 if (is_enabled != NULL) {
  24                         memcpy(new_enabled, is_enabled, enabled_len*sizeof(bool));
  25                         free(is_enabled);
  26                 }
  27                 is_enabled=new_enabled;
  28                 enabled_len=threadid+1;
  29         }
  30         is_enabled[threadid]=enabled_status;
  31 }
  32
  33 /**
  34  * Add a Thread to the scheduler's ready list.
  35  * @param t The Thread to add
  36  */
  37 void Scheduler::add_thread(Thread *t)
  38 {
  39         DEBUG("thread %d\n", t->get_id());
  40         set_enabled(t, true);
  41 }
  42
  43 /**
  44  * Remove a given Thread from the scheduler.
  45  * @param t The Thread to remove
  46  */
  47 void Scheduler::remove_thread(Thread *t)
  48 {
  49         if (current == t)
  50                 current = NULL;
  51         set_enabled(t, false);
  52 }
  53
  54 /**
  55  * Prevent a Thread from being scheduled. The sleeping Thread should be
  56  * re-awoken via Scheduler::wake.
  57  * @param thread The Thread that should sleep
  58  */
  59 void Scheduler::sleep(Thread *t)
  60 {
  61         set_enabled(t, false);
  62         t->set_state(THREAD_BLOCKED);
  63 }
  64
  65 /**
  66  * Wake a Thread up that was previously waiting (see Scheduler::wait)
  67  * @param t The Thread to wake up
  68  */
  69 void Scheduler::wake(Thread *t)
  70 {
  71         set_enabled(t, true);
  72         t->set_state(THREAD_READY);
  73 }
  74
  75 /**
  76  * Select a Thread. This implementation defaults to round-robin, if a
  77  * thread is not already provided.
  78  *
  79  * @param t Thread to run, if chosen by an external entity (e.g.,
  80  * ModelChecker). May be NULL to indicate no external choice.
  81  * @return The next Thread to run
  82  */
  83 Thread * Scheduler::next_thread(Thread *t)
  84 {
  85         if ( t == NULL ) {
  86                 int old_curr_thread = curr_thread_index;
  87                 while(true) {
  88                         curr_thread_index = (curr_thread_index+1) % enabled_len;
  89                         if (is_enabled[curr_thread_index]) {
  90                                 t = model->get_thread(int_to_id(curr_thread_index));
  91                                 break;
  92                         }
  93                         if (curr_thread_index == old_curr_thread) {
  94                                 print();
  95                                 return NULL;
  96                         }
  97                 }
  98         } else {
  99                 curr_thread_index = id_to_int(t->get_id());
 100         }
 101
 102         current = t;
 103         print();
 104         return t;
 105 }
 106
 107 /**
 108  * @return The currently-running Thread
 109  */
 110 Thread * Scheduler::get_current_thread() const
 111 {
 112         return current;
 113 }
 114
 115 /**
 116  * Print debugging information about the current state of the scheduler. Only
 117  * prints something if debugging is enabled.
 118  */
 119 void Scheduler::print() const
 120 {
 121         if (current)
 122                 DEBUG("Current thread: %d\n", current->get_id());
 123         else
 124                 DEBUG("No current thread\n");
 125 }