ghc/rts/Task.c

   1 /* -----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team 2001-2005
   4  *
   5  * The task manager subsystem.  Tasks execute STG code, with this
   6  * module providing the API which the Scheduler uses to control their
   7  * creation and destruction.
   8  *
   9  * -------------------------------------------------------------------------*/
  10
  11 #include "Rts.h"
  12 #include "RtsUtils.h"
  13 #include "OSThreads.h"
  14 #include "Task.h"
  15 #include "Capability.h"
  16 #include "Stats.h"
  17 #include "RtsFlags.h"
  18 #include "Schedule.h"
  19 #include "Hash.h"
  20
  21 #if HAVE_SIGNAL_H
  22 #include <signal.h>
  23 #endif
  24
  25 // Task lists and global counters.
  26 // Locks required: sched_mutex.
  27 Task *all_tasks = NULL;
  28 static Task *task_free_list = NULL; // singly-linked
  29 static nat taskCount;
  30 #define DEFAULT_MAX_WORKERS 64
  31 static nat maxWorkers; // we won't create more workers than this
  32 static nat tasksRunning;
  33 static nat workerCount;
  34
  35 /* -----------------------------------------------------------------------------
  36  * Remembering the current thread's Task
  37  * -------------------------------------------------------------------------- */
  38
  39 // A thread-local-storage key that we can use to get access to the
  40 // current thread's Task structure.
  41 #if defined(THREADED_RTS)
  42 ThreadLocalKey currentTaskKey;
  43 #else
  44 Task *my_task;
  45 #endif
  46
  47 /* -----------------------------------------------------------------------------
  48  * Rest of the Task API
  49  * -------------------------------------------------------------------------- */
  50
  51 void
  52 initTaskManager (void)
  53 {
  54     static int initialized = 0;
  55
  56     if (!initialized) {
  57         taskCount = 0;
  58         workerCount = 0;
  59         tasksRunning = 0;
  60         maxWorkers = DEFAULT_MAX_WORKERS;
  61         initialized = 1;
  62 #if defined(THREADED_RTS)
  63         newThreadLocalKey(&currentTaskKey);
  64 #endif
  65     }
  66 }
  67
  68
  69 void
  70 stopTaskManager (void)
  71 {
  72     IF_DEBUG(scheduler, sched_belch("stopping task manager, %d tasks still running", tasksRunning));
  73 }
  74
  75
  76 static Task*
  77 newTask (void)
  78 {
  79 #if defined(THREADED_RTS)
  80     long currentElapsedTime, currentUserTime, elapsedGCTime;
  81 #endif
  82     Task *task;
  83
  84     task = stgMallocBytes(sizeof(Task), "newTask");
  85
  86     task->cap  = NULL;
  87     task->stopped = rtsFalse;
  88     task->suspended_tso = NULL;
  89     task->tso  = NULL;
  90     task->stat = NoStatus;
  91     task->ret  = NULL;
  92
  93 #if defined(THREADED_RTS)
  94     initCondition(&task->cond);
  95     initMutex(&task->lock);
  96     task->wakeup = rtsFalse;
  97 #endif
  98
  99 #if defined(THREADED_RTS)
 100     stat_getTimes(&currentElapsedTime, &currentUserTime, &elapsedGCTime);
 101     task->mut_time = 0.0;
 102     task->mut_etime = 0.0;
 103     task->gc_time = 0.0;
 104     task->gc_etime = 0.0;
 105     task->muttimestart = currentUserTime;
 106     task->elapsedtimestart = currentElapsedTime;
 107 #endif
 108
 109     task->prev = NULL;
 110     task->next = NULL;
 111     task->return_link = NULL;
 112
 113     task->all_link = all_tasks;
 114     all_tasks = task;
 115
 116     taskCount++;
 117     workerCount++;
 118
 119     return task;
 120 }
 121
 122 Task *
 123 newBoundTask (void)
 124 {
 125     Task *task;
 126
 127     ASSERT_LOCK_HELD(&sched_mutex);
 128     if (task_free_list == NULL) {
 129         task = newTask();
 130     } else {
 131         task = task_free_list;
 132         task_free_list = task->next;
 133         task->next = NULL;
 134         task->prev = NULL;
 135         task->stopped = rtsFalse;
 136     }
 137 #if defined(THREADED_RTS)
 138     task->id = osThreadId();
 139 #endif
 140     ASSERT(task->cap == NULL);
 141
 142     tasksRunning++;
 143
 144     taskEnter(task);
 145
 146     IF_DEBUG(scheduler,sched_belch("new task (taskCount: %d)", taskCount););
 147     return task;
 148 }
 149
 150 void
 151 boundTaskExiting (Task *task)
 152 {
 153     task->stopped = rtsTrue;
 154     task->cap = NULL;
 155
 156 #if defined(THREADED_RTS)
 157     ASSERT(osThreadId() == task->id);
 158 #endif
 159     ASSERT(myTask() == task);
 160     setMyTask(task->prev_stack);
 161
 162     tasksRunning--;
 163
 164     // sadly, we need a lock around the free task list. Todo: eliminate.
 165     ACQUIRE_LOCK(&sched_mutex);
 166     task->next = task_free_list;
 167     task_free_list = task;
 168     RELEASE_LOCK(&sched_mutex);
 169
 170     IF_DEBUG(scheduler,sched_belch("task exiting"));
 171 }
 172
 173 void
 174 discardTask (Task *task)
 175 {
 176     ASSERT_LOCK_HELD(&sched_mutex);
 177 #if defined(THREADED_RTS)
 178     closeCondition(&task->cond);
 179 #endif
 180     task->stopped = rtsTrue;
 181     task->cap = NULL;
 182     task->next = task_free_list;
 183     task_free_list = task;
 184 }
 185
 186 void
 187 taskStop (Task *task)
 188 {
 189 #if defined(THREADED_RTS)
 190     OSThreadId id;
 191     long currentElapsedTime, currentUserTime, elapsedGCTime;
 192
 193     id = osThreadId();
 194     ASSERT(task->id == id);
 195     ASSERT(myTask() == task);
 196
 197     stat_getTimes(&currentElapsedTime, &currentUserTime, &elapsedGCTime);
 198
 199     task->mut_time =
 200         currentUserTime - task->muttimestart - task->gc_time;
 201     task->mut_etime =
 202         currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
 203
 204     if (task->mut_time < 0.0)  { task->mut_time = 0.0;  }
 205     if (task->mut_etime < 0.0) { task->mut_etime = 0.0; }
 206 #endif
 207
 208     task->stopped = rtsTrue;
 209     tasksRunning--;
 210 }
 211
 212 void
 213 resetTaskManagerAfterFork (void)
 214 {
 215 #warning TODO!
 216     taskCount = 0;
 217 }
 218
 219 #if defined(THREADED_RTS)
 220
 221 void
 222 startWorkerTask (Capability *cap,
 223                  void OSThreadProcAttr (*taskStart)(Task *task))
 224 {
 225   int r;
 226   OSThreadId tid;
 227   Task *task;
 228
 229   if (workerCount >= maxWorkers) {
 230       barf("too many workers; runaway worker creation?");
 231   }
 232   workerCount++;
 233
 234   // A worker always gets a fresh Task structure.
 235   task = newTask();
 236
 237   tasksRunning++;
 238
 239   // The lock here is to synchronise with taskStart(), to make sure
 240   // that we have finished setting up the Task structure before the
 241   // worker thread reads it.
 242   ACQUIRE_LOCK(&task->lock);
 243
 244   task->cap = cap;
 245
 246   // Give the capability directly to the worker; we can't let anyone
 247   // else get in, because the new worker Task has nowhere to go to
 248   // sleep so that it could be woken up again.
 249   ASSERT_LOCK_HELD(&cap->lock);
 250   cap->running_task = task;
 251
 252   r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
 253   if (r != 0) {
 254     barf("startTask: Can't create new task");
 255   }
 256
 257   IF_DEBUG(scheduler,sched_belch("new worker task (taskCount: %d)", taskCount););
 258
 259   task->id = tid;
 260
 261   // ok, finished with the Task struct.
 262   RELEASE_LOCK(&task->lock);
 263 }
 264
 265 #endif /* THREADED_RTS */
 266
 267 #ifdef DEBUG
 268
 269 static void *taskId(Task *task)
 270 {
 271 #ifdef THREADED_RTS
 272     return (void *)task->id;
 273 #else
 274     return (void *)task;
 275 #endif
 276 }
 277
 278 void printAllTasks(void);
 279
 280 void
 281 printAllTasks(void)
 282 {
 283     Task *task;
 284     for (task = all_tasks; task != NULL; task = task->all_link) {
 285         debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
 286         if (!task->stopped) {
 287             if (task->cap) {
 288                 debugBelch("on capability %d, ", task->cap->no);
 289             }
 290             if (task->tso) {
 291                 debugBelch("bound to thread %d", task->tso->id);
 292             } else {
 293                 debugBelch("worker");
 294             }
 295         }
 296         debugBelch("\n");
 297     }
 298 }
 299
 300 #endif
 301