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 #if defined(THREADED_RTS)
  88         closeCondition(&task->cond);
  89         closeMutex(&task->lock);
  90 #endif
  91         next = task->all_link;
  92         stgFree(task);
  93     }
  94     all_tasks = NULL;
  95     task_free_list = NULL;
  96     RELEASE_LOCK(&sched_mutex);
  97 }
  98
  99
 100 static Task*
 101 newTask (void)
 102 {
 103 #if defined(THREADED_RTS)
 104     Ticks currentElapsedTime, currentUserTime;
 105 #endif
 106     Task *task;
 107
 108     task = stgMallocBytes(sizeof(Task), "newTask");
 109
 110     task->cap  = NULL;
 111     task->stopped = rtsFalse;
 112     task->suspended_tso = NULL;
 113     task->tso  = NULL;
 114     task->stat = NoStatus;
 115     task->ret  = NULL;
 116
 117 #if defined(THREADED_RTS)
 118     initCondition(&task->cond);
 119     initMutex(&task->lock);
 120     task->wakeup = rtsFalse;
 121 #endif
 122
 123 #if defined(THREADED_RTS)
 124     currentUserTime = getThreadCPUTime();
 125     currentElapsedTime = getProcessElapsedTime();
 126     task->mut_time = 0;
 127     task->mut_etime = 0;
 128     task->gc_time = 0;
 129     task->gc_etime = 0;
 130     task->muttimestart = currentUserTime;
 131     task->elapsedtimestart = currentElapsedTime;
 132 #endif
 133
 134     task->prev = NULL;
 135     task->next = NULL;
 136     task->return_link = NULL;
 137
 138     task->all_link = all_tasks;
 139     all_tasks = task;
 140
 141     taskCount++;
 142     workerCount++;
 143
 144     return task;
 145 }
 146
 147 Task *
 148 newBoundTask (void)
 149 {
 150     Task *task;
 151
 152     ASSERT_LOCK_HELD(&sched_mutex);
 153     if (task_free_list == NULL) {
 154         task = newTask();
 155     } else {
 156         task = task_free_list;
 157         task_free_list = task->next;
 158         task->next = NULL;
 159         task->prev = NULL;
 160         task->stopped = rtsFalse;
 161     }
 162 #if defined(THREADED_RTS)
 163     task->id = osThreadId();
 164 #endif
 165     ASSERT(task->cap == NULL);
 166
 167     tasksRunning++;
 168
 169     taskEnter(task);
 170
 171     debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
 172     return task;
 173 }
 174
 175 void
 176 boundTaskExiting (Task *task)
 177 {
 178     task->stopped = rtsTrue;
 179     task->cap = NULL;
 180
 181 #if defined(THREADED_RTS)
 182     ASSERT(osThreadId() == task->id);
 183 #endif
 184     ASSERT(myTask() == task);
 185     setMyTask(task->prev_stack);
 186
 187     tasksRunning--;
 188
 189     // sadly, we need a lock around the free task list. Todo: eliminate.
 190     ACQUIRE_LOCK(&sched_mutex);
 191     task->next = task_free_list;
 192     task_free_list = task;
 193     RELEASE_LOCK(&sched_mutex);
 194
 195     debugTrace(DEBUG_sched, "task exiting");
 196 }
 197
 198 #ifdef THREADED_RTS
 199 #define TASK_ID(t) (t)->id
 200 #else
 201 #define TASK_ID(t) (t)
 202 #endif
 203
 204 void
 205 discardTask (Task *task)
 206 {
 207     ASSERT_LOCK_HELD(&sched_mutex);
 208     if (!task->stopped) {
 209         debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
 210         task->cap = NULL;
 211         task->tso = NULL;
 212         task->stopped = rtsTrue;
 213         tasksRunning--;
 214         task->next = task_free_list;
 215         task_free_list = task;
 216     }
 217 }
 218
 219 void
 220 taskTimeStamp (Task *task USED_IF_THREADS)
 221 {
 222 #if defined(THREADED_RTS)
 223     Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
 224
 225     currentUserTime = getThreadCPUTime();
 226     currentElapsedTime = getProcessElapsedTime();
 227
 228     // XXX this is wrong; we want elapsed GC time since the
 229     // Task started.
 230     elapsedGCTime = stat_getElapsedGCTime();
 231
 232     task->mut_time =
 233         currentUserTime - task->muttimestart - task->gc_time;
 234     task->mut_etime =
 235         currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
 236
 237     if (task->mut_time  < 0) { task->mut_time  = 0; }
 238     if (task->mut_etime < 0) { task->mut_etime = 0; }
 239 #endif
 240 }
 241
 242 void
 243 workerTaskStop (Task *task)
 244 {
 245 #if defined(THREADED_RTS)
 246     OSThreadId id;
 247     id = osThreadId();
 248     ASSERT(task->id == id);
 249     ASSERT(myTask() == task);
 250 #endif
 251
 252     taskTimeStamp(task);
 253     task->stopped = rtsTrue;
 254     tasksRunning--;
 255
 256     ACQUIRE_LOCK(&sched_mutex);
 257     task->next = task_free_list;
 258     task_free_list = task;
 259     RELEASE_LOCK(&sched_mutex);
 260 }
 261
 262 void
 263 resetTaskManagerAfterFork (void)
 264 {
 265     // TODO!
 266     taskCount = 0;
 267 }
 268
 269 #if defined(THREADED_RTS)
 270
 271 void
 272 startWorkerTask (Capability *cap,
 273                  void OSThreadProcAttr (*taskStart)(Task *task))
 274 {
 275   int r;
 276   OSThreadId tid;
 277   Task *task;
 278
 279   workerCount++;
 280
 281   // A worker always gets a fresh Task structure.
 282   task = newTask();
 283
 284   tasksRunning++;
 285
 286   // The lock here is to synchronise with taskStart(), to make sure
 287   // that we have finished setting up the Task structure before the
 288   // worker thread reads it.
 289   ACQUIRE_LOCK(&task->lock);
 290
 291   task->cap = cap;
 292
 293   // Give the capability directly to the worker; we can't let anyone
 294   // else get in, because the new worker Task has nowhere to go to
 295   // sleep so that it could be woken up again.
 296   ASSERT_LOCK_HELD(&cap->lock);
 297   cap->running_task = task;
 298
 299   r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
 300   if (r != 0) {
 301     sysErrorBelch("failed to create OS thread");
 302     stg_exit(EXIT_FAILURE);
 303   }
 304
 305   debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
 306
 307   task->id = tid;
 308
 309   // ok, finished with the Task struct.
 310   RELEASE_LOCK(&task->lock);
 311 }
 312
 313 #endif /* THREADED_RTS */
 314
 315 #ifdef DEBUG
 316
 317 static void *taskId(Task *task)
 318 {
 319 #ifdef THREADED_RTS
 320     return (void *)task->id;
 321 #else
 322     return (void *)task;
 323 #endif
 324 }
 325
 326 void printAllTasks(void);
 327
 328 void
 329 printAllTasks(void)
 330 {
 331     Task *task;
 332     for (task = all_tasks; task != NULL; task = task->all_link) {
 333         debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
 334         if (!task->stopped) {
 335             if (task->cap) {
 336                 debugBelch("on capability %d, ", task->cap->no);
 337             }
 338             if (task->tso) {
 339               debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
 340             } else {
 341                 debugBelch("worker");
 342             }
 343         }
 344         debugBelch("\n");
 345     }
 346 }
 347
 348 #endif
 349