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         ASSERT(!t->is_model_thread());
  52         set_enabled(t, THREAD_ENABLED);
  53 }
  54
  55 /**
  56  * Remove a given Thread from the scheduler.
  57  * @param t The Thread to remove
  58  */
  59 void Scheduler::remove_thread(Thread *t)
  60 {
  61         if (current == t)
  62                 current = NULL;
  63         set_enabled(t, THREAD_DISABLED);
  64 }
  65
  66 /**
  67  * Prevent a Thread from being scheduled. The sleeping Thread should be
  68  * re-awoken via Scheduler::wake.
  69  * @param thread The Thread that should sleep
  70  */
  71 void Scheduler::sleep(Thread *t)
  72 {
  73         set_enabled(t, THREAD_DISABLED);
  74         t->set_state(THREAD_BLOCKED);
  75 }
  76
  77 /**
  78  * Wake a Thread up that was previously waiting (see Scheduler::wait)
  79  * @param t The Thread to wake up
  80  */
  81 void Scheduler::wake(Thread *t)
  82 {
  83         ASSERT(!t->is_model_thread());
  84         set_enabled(t, THREAD_DISABLED);
  85         t->set_state(THREAD_READY);
  86 }
  87
  88 /**
  89  * Select a Thread. This implementation defaults to round-robin, if a
  90  * thread is not already provided.
  91  *
  92  * @param t Thread to run, if chosen by an external entity (e.g.,
  93  * ModelChecker). May be NULL to indicate no external choice.
  94  * @return The next Thread to run
  95  */
  96 Thread * Scheduler::next_thread(Thread *t)
  97 {
  98         if ( t == NULL ) {
  99                 int old_curr_thread = curr_thread_index;
 100                 while(true) {
 101                         curr_thread_index = (curr_thread_index+1) % enabled_len;
 102                         if (enabled[curr_thread_index]) {
 103                                 t = model->get_thread(int_to_id(curr_thread_index));
 104                                 break;
 105                         }
 106                         if (curr_thread_index == old_curr_thread) {
 107                                 print();
 108                                 return NULL;
 109                         }
 110                 }
 111         } else if (t->is_model_thread()) {
 112                 /* model-checker threads never run */
 113                 t = NULL;
 114         } else {
 115                 curr_thread_index = id_to_int(t->get_id());
 116         }
 117
 118         current = t;
 119         print();
 120         return t;
 121 }
 122
 123 /**
 124  * @return The currently-running Thread
 125  */
 126 Thread * Scheduler::get_current_thread() const
 127 {
 128         ASSERT(!current || !current->is_model_thread());
 129         return current;
 130 }
 131
 132 /**
 133  * Print debugging information about the current state of the scheduler. Only
 134  * prints something if debugging is enabled.
 135  */
 136 void Scheduler::print() const
 137 {
 138         if (current)
 139                 DEBUG("Current thread: %d\n", id_to_int(current->get_id()));
 140         else
 141                 DEBUG("No current thread\n");
 142 }