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         enabled(NULL),
  12         enabled_len(0),
  13         curr_thread_index(0),
  14         current(NULL)
  15 {
  16 }
  17
  18 void Scheduler::set_enabled(Thread *t, enabled_type_t enabled_status) {
  19         int threadid=id_to_int(t->get_id());
  20         if (threadid>=enabled_len) {
  21                 enabled_type_t *new_enabled = (enabled_type_t *)snapshot_malloc(sizeof(enabled_type_t) * (threadid + 1));
  22                 memset(&new_enabled[enabled_len], 0, (threadid+1-enabled_len)*sizeof(enabled_type_t));
  23                 if (enabled != NULL) {
  24                         memcpy(new_enabled, enabled, enabled_len*sizeof(enabled_type_t));
  25                         snapshot_free(enabled);
  26                 }
  27                 enabled=new_enabled;
  28                 enabled_len=threadid+1;
  29         }
  30         enabled[threadid]=enabled_status;
  31 }
  32
  33 /**
  34  * @brief Check if a Thread is currently enabled
  35  * @param t The Thread to check
  36  * @return True if the Thread is currently enabled
  37  */
  38 bool Scheduler::is_enabled(Thread *t) const
  39 {
  40         int id = id_to_int(t->get_id());
  41         return (id >= enabled_len) ? false : (enabled[id] == THREAD_ENABLED);
  42 }
  43
  44 /**
  45  * Add a Thread to the scheduler's ready list.
  46  * @param t The Thread to add
  47  */
  48 void Scheduler::add_thread(Thread *t)
  49 {
  50         DEBUG("thread %d\n", id_to_int(t->get_id()));
  51         set_enabled(t, THREAD_ENABLED);
  52 }
  53
  54 /**
  55  * Remove a given Thread from the scheduler.
  56  * @param t The Thread to remove
  57  */
  58 void Scheduler::remove_thread(Thread *t)
  59 {
  60         if (current == t)
  61                 current = NULL;
  62         set_enabled(t, THREAD_DISABLED);
  63 }
  64
  65 /**
  66  * Prevent a Thread from being scheduled. The sleeping Thread should be
  67  * re-awoken via Scheduler::wake.
  68  * @param thread The Thread that should sleep
  69  */
  70 void Scheduler::sleep(Thread *t)
  71 {
  72         set_enabled(t, THREAD_DISABLED);
  73         t->set_state(THREAD_BLOCKED);
  74 }
  75
  76 /**
  77  * Wake a Thread up that was previously waiting (see Scheduler::wait)
  78  * @param t The Thread to wake up
  79  */
  80 void Scheduler::wake(Thread *t)
  81 {
  82         set_enabled(t, THREAD_DISABLED);
  83         t->set_state(THREAD_READY);
  84 }
  85
  86 /**
  87  * Select a Thread. This implementation defaults to round-robin, if a
  88  * thread is not already provided.
  89  *
  90  * @param t Thread to run, if chosen by an external entity (e.g.,
  91  * ModelChecker). May be NULL to indicate no external choice.
  92  * @return The next Thread to run
  93  */
  94 Thread * Scheduler::next_thread(Thread *t)
  95 {
  96         if ( t == NULL ) {
  97                 int old_curr_thread = curr_thread_index;
  98                 while(true) {
  99                         curr_thread_index = (curr_thread_index+1) % enabled_len;
 100                         if (enabled[curr_thread_index]) {
 101                                 t = model->get_thread(int_to_id(curr_thread_index));
 102                                 break;
 103                         }
 104                         if (curr_thread_index == old_curr_thread) {
 105                                 print();
 106                                 return NULL;
 107                         }
 108                 }
 109         } else {
 110                 curr_thread_index = id_to_int(t->get_id());
 111         }
 112
 113         current = t;
 114         print();
 115         return t;
 116 }
 117
 118 /**
 119  * @return The currently-running Thread
 120  */
 121 Thread * Scheduler::get_current_thread() const
 122 {
 123         return current;
 124 }
 125
 126 /**
 127  * Print debugging information about the current state of the scheduler. Only
 128  * prints something if debugging is enabled.
 129  */
 130 void Scheduler::print() const
 131 {
 132         if (current)
 133                 DEBUG("Current thread: %d\n", id_to_int(current->get_id()));
 134         else
 135                 DEBUG("No current thread\n");
 136 }