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     Ticks currentElapsedTime, currentUserTime;
  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     currentUserTime = getThreadCPUTime();
 101     currentElapsedTime = getProcessElapsedTime();
 102     task->mut_time = 0.0;
 103     task->mut_etime = 0.0;
 104     task->gc_time = 0.0;
 105     task->gc_etime = 0.0;
 106     task->muttimestart = currentUserTime;
 107     task->elapsedtimestart = currentElapsedTime;
 108 #endif
 109
 110     task->prev = NULL;
 111     task->next = NULL;
 112     task->return_link = NULL;
 113
 114     task->all_link = all_tasks;
 115     all_tasks = task;
 116
 117     taskCount++;
 118     workerCount++;
 119
 120     return task;
 121 }
 122
 123 Task *
 124 newBoundTask (void)
 125 {
 126     Task *task;
 127
 128     ASSERT_LOCK_HELD(&sched_mutex);
 129     if (task_free_list == NULL) {
 130         task = newTask();
 131     } else {
 132         task = task_free_list;
 133         task_free_list = task->next;
 134         task->next = NULL;
 135         task->prev = NULL;
 136         task->stopped = rtsFalse;
 137     }
 138 #if defined(THREADED_RTS)
 139     task->id = osThreadId();
 140 #endif
 141     ASSERT(task->cap == NULL);
 142
 143     tasksRunning++;
 144
 145     taskEnter(task);
 146
 147     IF_DEBUG(scheduler,sched_belch("new task (taskCount: %d)", taskCount););
 148     return task;
 149 }
 150
 151 void
 152 boundTaskExiting (Task *task)
 153 {
 154     task->stopped = rtsTrue;
 155     task->cap = NULL;
 156
 157 #if defined(THREADED_RTS)
 158     ASSERT(osThreadId() == task->id);
 159 #endif
 160     ASSERT(myTask() == task);
 161     setMyTask(task->prev_stack);
 162
 163     tasksRunning--;
 164
 165     // sadly, we need a lock around the free task list. Todo: eliminate.
 166     ACQUIRE_LOCK(&sched_mutex);
 167     task->next = task_free_list;
 168     task_free_list = task;
 169     RELEASE_LOCK(&sched_mutex);
 170
 171     IF_DEBUG(scheduler,sched_belch("task exiting"));
 172 }
 173
 174 void
 175 discardTask (Task *task)
 176 {
 177     ASSERT_LOCK_HELD(&sched_mutex);
 178     if (!task->stopped) {
 179         IF_DEBUG(scheduler,sched_belch("discarding task %p",(void *)task->id));
 180         task->cap = NULL;
 181         task->tso = NULL;
 182         task->stopped = rtsTrue;
 183         tasksRunning--;
 184         task->next = task_free_list;
 185         task_free_list = task;
 186     }
 187 }
 188
 189 void
 190 taskStop (Task *task)
 191 {
 192 #if defined(THREADED_RTS)
 193     OSThreadId id;
 194     Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
 195
 196     id = osThreadId();
 197     ASSERT(task->id == id);
 198     ASSERT(myTask() == task);
 199
 200     currentUserTime = getThreadCPUTime();
 201     currentElapsedTime = getProcessElapsedTime();
 202
 203     // XXX this is wrong; we want elapsed GC time since the
 204     // Task started.
 205     elapsedGCTime = stat_getElapsedGCTime();
 206
 207     task->mut_time =
 208         currentUserTime - task->muttimestart - task->gc_time;
 209     task->mut_etime =
 210         currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
 211
 212     if (task->mut_time < 0.0)  { task->mut_time = 0.0;  }
 213     if (task->mut_etime < 0.0) { task->mut_etime = 0.0; }
 214 #endif
 215
 216     task->stopped = rtsTrue;
 217     tasksRunning--;
 218 }
 219
 220 void
 221 resetTaskManagerAfterFork (void)
 222 {
 223 #warning TODO!
 224     taskCount = 0;
 225 }
 226
 227 #if defined(THREADED_RTS)
 228
 229 void
 230 startWorkerTask (Capability *cap,
 231                  void OSThreadProcAttr (*taskStart)(Task *task))
 232 {
 233   int r;
 234   OSThreadId tid;
 235   Task *task;
 236
 237   if (workerCount >= maxWorkers) {
 238       barf("too many workers; runaway worker creation?");
 239   }
 240   workerCount++;
 241
 242   // A worker always gets a fresh Task structure.
 243   task = newTask();
 244
 245   tasksRunning++;
 246
 247   // The lock here is to synchronise with taskStart(), to make sure
 248   // that we have finished setting up the Task structure before the
 249   // worker thread reads it.
 250   ACQUIRE_LOCK(&task->lock);
 251
 252   task->cap = cap;
 253
 254   // Give the capability directly to the worker; we can't let anyone
 255   // else get in, because the new worker Task has nowhere to go to
 256   // sleep so that it could be woken up again.
 257   ASSERT_LOCK_HELD(&cap->lock);
 258   cap->running_task = task;
 259
 260   r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
 261   if (r != 0) {
 262     barf("startTask: Can't create new task");
 263   }
 264
 265   IF_DEBUG(scheduler,sched_belch("new worker task (taskCount: %d)", taskCount););
 266
 267   task->id = tid;
 268
 269   // ok, finished with the Task struct.
 270   RELEASE_LOCK(&task->lock);
 271 }
 272
 273 #endif /* THREADED_RTS */
 274
 275 #ifdef DEBUG
 276
 277 static void *taskId(Task *task)
 278 {
 279 #ifdef THREADED_RTS
 280     return (void *)task->id;
 281 #else
 282     return (void *)task;
 283 #endif
 284 }
 285
 286 void printAllTasks(void);
 287
 288 void
 289 printAllTasks(void)
 290 {
 291     Task *task;
 292     for (task = all_tasks; task != NULL; task = task->all_link) {
 293         debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
 294         if (!task->stopped) {
 295             if (task->cap) {
 296                 debugBelch("on capability %d, ", task->cap->no);
 297             }
 298             if (task->tso) {
 299                 debugBelch("bound to thread %d", task->tso->id);
 300             } else {
 301                 debugBelch("worker");
 302             }
 303         }
 304         debugBelch("\n");
 305     }
 306 }
 307
 308 #endif
 309