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 "Storage.h"
  19 #include "Schedule.h"
  20 #include "Hash.h"
  21 #include "Trace.h"
  22
  23 #if HAVE_SIGNAL_H
  24 #include <signal.h>
  25 #endif
  26
  27 // Task lists and global counters.
  28 // Locks required: sched_mutex.
  29 Task *all_tasks = NULL;
  30 static Task *task_free_list = NULL; // singly-linked
  31 static nat taskCount;
  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         initialized = 1;
  61 #if defined(THREADED_RTS)
  62         newThreadLocalKey(&currentTaskKey);
  63 #endif
  64     }
  65 }
  66
  67
  68 void
  69 stopTaskManager (void)
  70 {
  71     debugTrace(DEBUG_sched,
  72                "stopping task manager, %d tasks still running",
  73                tasksRunning);
  74     /* nothing to do */
  75 }
  76
  77
  78 void
  79 freeTaskManager (void)
  80 {
  81     Task *task, *next;
  82
  83     debugTrace(DEBUG_sched, "freeing task manager");
  84
  85     ACQUIRE_LOCK(&sched_mutex);
  86     for (task = all_tasks; task != NULL; task = next) {
  87         next = task->all_link;
  88         if (task->stopped) {
  89             // We only free resources if the Task is not in use.  A
  90             // Task may still be in use if we have a Haskell thread in
  91             // a foreign call while we are attempting to shut down the
  92             // RTS (see conc059).
  93 #if defined(THREADED_RTS)
  94             closeCondition(&task->cond);
  95             closeMutex(&task->lock);
  96 #endif
  97             stgFree(task);
  98         }
  99     }
 100     all_tasks = NULL;
 101     task_free_list = NULL;
 102 #if defined(THREADED_RTS)
 103     freeThreadLocalKey(&currentTaskKey);
 104 #endif
 105     RELEASE_LOCK(&sched_mutex);
 106 }
 107
 108
 109 static Task*
 110 newTask (void)
 111 {
 112 #if defined(THREADED_RTS)
 113     Ticks currentElapsedTime, currentUserTime;
 114 #endif
 115     Task *task;
 116
 117     task = stgMallocBytes(sizeof(Task), "newTask");
 118
 119     task->cap  = NULL;
 120     task->stopped = rtsFalse;
 121     task->suspended_tso = NULL;
 122     task->tso  = NULL;
 123     task->stat = NoStatus;
 124     task->ret  = NULL;
 125
 126 #if defined(THREADED_RTS)
 127     initCondition(&task->cond);
 128     initMutex(&task->lock);
 129     task->wakeup = rtsFalse;
 130 #endif
 131
 132 #if defined(THREADED_RTS)
 133     currentUserTime = getThreadCPUTime();
 134     currentElapsedTime = getProcessElapsedTime();
 135     task->mut_time = 0;
 136     task->mut_etime = 0;
 137     task->gc_time = 0;
 138     task->gc_etime = 0;
 139     task->muttimestart = currentUserTime;
 140     task->elapsedtimestart = currentElapsedTime;
 141 #endif
 142
 143     task->prev = NULL;
 144     task->next = NULL;
 145     task->return_link = NULL;
 146
 147     task->all_link = all_tasks;
 148     all_tasks = task;
 149
 150     taskCount++;
 151     workerCount++;
 152
 153     return task;
 154 }
 155
 156 Task *
 157 newBoundTask (void)
 158 {
 159     Task *task;
 160
 161     ASSERT_LOCK_HELD(&sched_mutex);
 162     if (task_free_list == NULL) {
 163         task = newTask();
 164     } else {
 165         task = task_free_list;
 166         task_free_list = task->next;
 167         task->next = NULL;
 168         task->prev = NULL;
 169         task->stopped = rtsFalse;
 170     }
 171 #if defined(THREADED_RTS)
 172     task->id = osThreadId();
 173 #endif
 174     ASSERT(task->cap == NULL);
 175
 176     tasksRunning++;
 177
 178     taskEnter(task);
 179
 180     debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
 181     return task;
 182 }
 183
 184 void
 185 boundTaskExiting (Task *task)
 186 {
 187     task->stopped = rtsTrue;
 188     task->cap = NULL;
 189
 190 #if defined(THREADED_RTS)
 191     ASSERT(osThreadId() == task->id);
 192 #endif
 193     ASSERT(myTask() == task);
 194     setMyTask(task->prev_stack);
 195
 196     tasksRunning--;
 197
 198     // sadly, we need a lock around the free task list. Todo: eliminate.
 199     ACQUIRE_LOCK(&sched_mutex);
 200     task->next = task_free_list;
 201     task_free_list = task;
 202     RELEASE_LOCK(&sched_mutex);
 203
 204     debugTrace(DEBUG_sched, "task exiting");
 205 }
 206
 207 #ifdef THREADED_RTS
 208 #define TASK_ID(t) (t)->id
 209 #else
 210 #define TASK_ID(t) (t)
 211 #endif
 212
 213 void
 214 discardTask (Task *task)
 215 {
 216     ASSERT_LOCK_HELD(&sched_mutex);
 217     if (!task->stopped) {
 218         debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
 219         task->cap = NULL;
 220         task->tso = NULL;
 221         task->stopped = rtsTrue;
 222         tasksRunning--;
 223         task->next = task_free_list;
 224         task_free_list = task;
 225     }
 226 }
 227
 228 void
 229 taskTimeStamp (Task *task USED_IF_THREADS)
 230 {
 231 #if defined(THREADED_RTS)
 232     Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
 233
 234     currentUserTime = getThreadCPUTime();
 235     currentElapsedTime = getProcessElapsedTime();
 236
 237     // XXX this is wrong; we want elapsed GC time since the
 238     // Task started.
 239     elapsedGCTime = stat_getElapsedGCTime();
 240
 241     task->mut_time =
 242         currentUserTime - task->muttimestart - task->gc_time;
 243     task->mut_etime =
 244         currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
 245
 246     if (task->mut_time  < 0) { task->mut_time  = 0; }
 247     if (task->mut_etime < 0) { task->mut_etime = 0; }
 248 #endif
 249 }
 250
 251 void
 252 workerTaskStop (Task *task)
 253 {
 254 #if defined(THREADED_RTS)
 255     OSThreadId id;
 256     id = osThreadId();
 257     ASSERT(task->id == id);
 258     ASSERT(myTask() == task);
 259 #endif
 260
 261     taskTimeStamp(task);
 262     task->stopped = rtsTrue;
 263     tasksRunning--;
 264
 265     ACQUIRE_LOCK(&sched_mutex);
 266     task->next = task_free_list;
 267     task_free_list = task;
 268     RELEASE_LOCK(&sched_mutex);
 269 }
 270
 271 void
 272 resetTaskManagerAfterFork (void)
 273 {
 274     // TODO!
 275     taskCount = 0;
 276 }
 277
 278 #if defined(THREADED_RTS)
 279
 280 void
 281 startWorkerTask (Capability *cap,
 282                  void OSThreadProcAttr (*taskStart)(Task *task))
 283 {
 284   int r;
 285   OSThreadId tid;
 286   Task *task;
 287
 288   workerCount++;
 289
 290   // A worker always gets a fresh Task structure.
 291   task = newTask();
 292
 293   tasksRunning++;
 294
 295   // The lock here is to synchronise with taskStart(), to make sure
 296   // that we have finished setting up the Task structure before the
 297   // worker thread reads it.
 298   ACQUIRE_LOCK(&task->lock);
 299
 300   task->cap = cap;
 301
 302   // Give the capability directly to the worker; we can't let anyone
 303   // else get in, because the new worker Task has nowhere to go to
 304   // sleep so that it could be woken up again.
 305   ASSERT_LOCK_HELD(&cap->lock);
 306   cap->running_task = task;
 307
 308   r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
 309   if (r != 0) {
 310     sysErrorBelch("failed to create OS thread");
 311     stg_exit(EXIT_FAILURE);
 312   }
 313
 314   debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
 315
 316   task->id = tid;
 317
 318   // ok, finished with the Task struct.
 319   RELEASE_LOCK(&task->lock);
 320 }
 321
 322 #endif /* THREADED_RTS */
 323
 324 #ifdef DEBUG
 325
 326 static void *taskId(Task *task)
 327 {
 328 #ifdef THREADED_RTS
 329     return (void *)task->id;
 330 #else
 331     return (void *)task;
 332 #endif
 333 }
 334
 335 void printAllTasks(void);
 336
 337 void
 338 printAllTasks(void)
 339 {
 340     Task *task;
 341     for (task = all_tasks; task != NULL; task = task->all_link) {
 342         debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
 343         if (!task->stopped) {
 344             if (task->cap) {
 345                 debugBelch("on capability %d, ", task->cap->no);
 346             }
 347             if (task->tso) {
 348               debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
 349             } else {
 350                 debugBelch("worker");
 351             }
 352         }
 353         debugBelch("\n");
 354     }
 355 }
 356
 357 #endif
 358