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     RELEASE_LOCK(&sched_mutex);
 103 }
 104
 105
 106 static Task*
 107 newTask (void)
 108 {
 109 #if defined(THREADED_RTS)
 110     Ticks currentElapsedTime, currentUserTime;
 111 #endif
 112     Task *task;
 113
 114     task = stgMallocBytes(sizeof(Task), "newTask");
 115
 116     task->cap  = NULL;
 117     task->stopped = rtsFalse;
 118     task->suspended_tso = NULL;
 119     task->tso  = NULL;
 120     task->stat = NoStatus;
 121     task->ret  = NULL;
 122
 123 #if defined(THREADED_RTS)
 124     initCondition(&task->cond);
 125     initMutex(&task->lock);
 126     task->wakeup = rtsFalse;
 127 #endif
 128
 129 #if defined(THREADED_RTS)
 130     currentUserTime = getThreadCPUTime();
 131     currentElapsedTime = getProcessElapsedTime();
 132     task->mut_time = 0;
 133     task->mut_etime = 0;
 134     task->gc_time = 0;
 135     task->gc_etime = 0;
 136     task->muttimestart = currentUserTime;
 137     task->elapsedtimestart = currentElapsedTime;
 138 #endif
 139
 140     task->prev = NULL;
 141     task->next = NULL;
 142     task->return_link = NULL;
 143
 144     task->all_link = all_tasks;
 145     all_tasks = task;
 146
 147     taskCount++;
 148     workerCount++;
 149
 150     return task;
 151 }
 152
 153 Task *
 154 newBoundTask (void)
 155 {
 156     Task *task;
 157
 158     ASSERT_LOCK_HELD(&sched_mutex);
 159     if (task_free_list == NULL) {
 160         task = newTask();
 161     } else {
 162         task = task_free_list;
 163         task_free_list = task->next;
 164         task->next = NULL;
 165         task->prev = NULL;
 166         task->stopped = rtsFalse;
 167     }
 168 #if defined(THREADED_RTS)
 169     task->id = osThreadId();
 170 #endif
 171     ASSERT(task->cap == NULL);
 172
 173     tasksRunning++;
 174
 175     taskEnter(task);
 176
 177     debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
 178     return task;
 179 }
 180
 181 void
 182 boundTaskExiting (Task *task)
 183 {
 184     task->stopped = rtsTrue;
 185     task->cap = NULL;
 186
 187 #if defined(THREADED_RTS)
 188     ASSERT(osThreadId() == task->id);
 189 #endif
 190     ASSERT(myTask() == task);
 191     setMyTask(task->prev_stack);
 192
 193     tasksRunning--;
 194
 195     // sadly, we need a lock around the free task list. Todo: eliminate.
 196     ACQUIRE_LOCK(&sched_mutex);
 197     task->next = task_free_list;
 198     task_free_list = task;
 199     RELEASE_LOCK(&sched_mutex);
 200
 201     debugTrace(DEBUG_sched, "task exiting");
 202 }
 203
 204 #ifdef THREADED_RTS
 205 #define TASK_ID(t) (t)->id
 206 #else
 207 #define TASK_ID(t) (t)
 208 #endif
 209
 210 void
 211 discardTask (Task *task)
 212 {
 213     ASSERT_LOCK_HELD(&sched_mutex);
 214     if (!task->stopped) {
 215         debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
 216         task->cap = NULL;
 217         task->tso = NULL;
 218         task->stopped = rtsTrue;
 219         tasksRunning--;
 220         task->next = task_free_list;
 221         task_free_list = task;
 222     }
 223 }
 224
 225 void
 226 taskTimeStamp (Task *task USED_IF_THREADS)
 227 {
 228 #if defined(THREADED_RTS)
 229     Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
 230
 231     currentUserTime = getThreadCPUTime();
 232     currentElapsedTime = getProcessElapsedTime();
 233
 234     // XXX this is wrong; we want elapsed GC time since the
 235     // Task started.
 236     elapsedGCTime = stat_getElapsedGCTime();
 237
 238     task->mut_time =
 239         currentUserTime - task->muttimestart - task->gc_time;
 240     task->mut_etime =
 241         currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
 242
 243     if (task->mut_time  < 0) { task->mut_time  = 0; }
 244     if (task->mut_etime < 0) { task->mut_etime = 0; }
 245 #endif
 246 }
 247
 248 void
 249 workerTaskStop (Task *task)
 250 {
 251 #if defined(THREADED_RTS)
 252     OSThreadId id;
 253     id = osThreadId();
 254     ASSERT(task->id == id);
 255     ASSERT(myTask() == task);
 256 #endif
 257
 258     taskTimeStamp(task);
 259     task->stopped = rtsTrue;
 260     tasksRunning--;
 261
 262     ACQUIRE_LOCK(&sched_mutex);
 263     task->next = task_free_list;
 264     task_free_list = task;
 265     RELEASE_LOCK(&sched_mutex);
 266 }
 267
 268 void
 269 resetTaskManagerAfterFork (void)
 270 {
 271     // TODO!
 272     taskCount = 0;
 273 }
 274
 275 #if defined(THREADED_RTS)
 276
 277 void
 278 startWorkerTask (Capability *cap,
 279                  void OSThreadProcAttr (*taskStart)(Task *task))
 280 {
 281   int r;
 282   OSThreadId tid;
 283   Task *task;
 284
 285   workerCount++;
 286
 287   // A worker always gets a fresh Task structure.
 288   task = newTask();
 289
 290   tasksRunning++;
 291
 292   // The lock here is to synchronise with taskStart(), to make sure
 293   // that we have finished setting up the Task structure before the
 294   // worker thread reads it.
 295   ACQUIRE_LOCK(&task->lock);
 296
 297   task->cap = cap;
 298
 299   // Give the capability directly to the worker; we can't let anyone
 300   // else get in, because the new worker Task has nowhere to go to
 301   // sleep so that it could be woken up again.
 302   ASSERT_LOCK_HELD(&cap->lock);
 303   cap->running_task = task;
 304
 305   r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
 306   if (r != 0) {
 307     sysErrorBelch("failed to create OS thread");
 308     stg_exit(EXIT_FAILURE);
 309   }
 310
 311   debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
 312
 313   task->id = tid;
 314
 315   // ok, finished with the Task struct.
 316   RELEASE_LOCK(&task->lock);
 317 }
 318
 319 #endif /* THREADED_RTS */
 320
 321 #ifdef DEBUG
 322
 323 static void *taskId(Task *task)
 324 {
 325 #ifdef THREADED_RTS
 326     return (void *)task->id;
 327 #else
 328     return (void *)task;
 329 #endif
 330 }
 331
 332 void printAllTasks(void);
 333
 334 void
 335 printAllTasks(void)
 336 {
 337     Task *task;
 338     for (task = all_tasks; task != NULL; task = task->all_link) {
 339         debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
 340         if (!task->stopped) {
 341             if (task->cap) {
 342                 debugBelch("on capability %d, ", task->cap->no);
 343             }
 344             if (task->tso) {
 345               debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
 346             } else {
 347                 debugBelch("worker");
 348             }
 349         }
 350         debugBelch("\n");
 351     }
 352 }
 353
 354 #endif
 355