1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 2001-2005
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.
9 * -------------------------------------------------------------------------*/
13 #include "OSThreads.h"
15 #include "Capability.h"
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
32 static nat tasksRunning;
33 static nat workerCount;
35 /* -----------------------------------------------------------------------------
36 * Remembering the current thread's Task
37 * -------------------------------------------------------------------------- */
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;
47 /* -----------------------------------------------------------------------------
48 * Rest of the Task API
49 * -------------------------------------------------------------------------- */
52 initTaskManager (void)
54 static int initialized = 0;
61 #if defined(THREADED_RTS)
62 newThreadLocalKey(¤tTaskKey);
69 stopTaskManager (void)
71 debugTrace(DEBUG_sched,
72 "stopping task manager, %d tasks still running",
79 freeTaskManager (void)
83 debugTrace(DEBUG_sched, "freeing task manager");
85 ACQUIRE_LOCK(&sched_mutex);
86 for (task = all_tasks; task != NULL; task = next) {
87 next = task->all_link;
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
93 #if defined(THREADED_RTS)
94 closeCondition(&task->cond);
95 closeMutex(&task->lock);
101 task_free_list = NULL;
102 #if defined(THREADED_RTS)
103 freeThreadLocalKey(¤tTaskKey);
105 RELEASE_LOCK(&sched_mutex);
112 #if defined(THREADED_RTS)
113 Ticks currentElapsedTime, currentUserTime;
117 #define ROUND_TO_CACHE_LINE(x) ((((x)+63) / 64) * 64)
118 task = stgMallocBytes(ROUND_TO_CACHE_LINE(sizeof(Task)), "newTask");
121 task->stopped = rtsFalse;
122 task->suspended_tso = NULL;
124 task->stat = NoStatus;
127 #if defined(THREADED_RTS)
128 initCondition(&task->cond);
129 initMutex(&task->lock);
130 task->wakeup = rtsFalse;
133 #if defined(THREADED_RTS)
134 currentUserTime = getThreadCPUTime();
135 currentElapsedTime = getProcessElapsedTime();
140 task->muttimestart = currentUserTime;
141 task->elapsedtimestart = currentElapsedTime;
146 task->return_link = NULL;
148 task->all_link = all_tasks;
162 ASSERT_LOCK_HELD(&sched_mutex);
163 if (task_free_list == NULL) {
166 task = task_free_list;
167 task_free_list = task->next;
170 task->stopped = rtsFalse;
172 #if defined(THREADED_RTS)
173 task->id = osThreadId();
175 ASSERT(task->cap == NULL);
181 debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
186 boundTaskExiting (Task *task)
188 task->stopped = rtsTrue;
191 #if defined(THREADED_RTS)
192 ASSERT(osThreadId() == task->id);
194 ASSERT(myTask() == task);
195 setMyTask(task->prev_stack);
199 // sadly, we need a lock around the free task list. Todo: eliminate.
200 ACQUIRE_LOCK(&sched_mutex);
201 task->next = task_free_list;
202 task_free_list = task;
203 RELEASE_LOCK(&sched_mutex);
205 debugTrace(DEBUG_sched, "task exiting");
209 #define TASK_ID(t) (t)->id
211 #define TASK_ID(t) (t)
215 discardTask (Task *task)
217 ASSERT_LOCK_HELD(&sched_mutex);
218 if (!task->stopped) {
219 debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
222 task->stopped = rtsTrue;
224 task->next = task_free_list;
225 task_free_list = task;
230 taskTimeStamp (Task *task USED_IF_THREADS)
232 #if defined(THREADED_RTS)
233 Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
235 currentUserTime = getThreadCPUTime();
236 currentElapsedTime = getProcessElapsedTime();
238 // XXX this is wrong; we want elapsed GC time since the
240 elapsedGCTime = stat_getElapsedGCTime();
243 currentUserTime - task->muttimestart - task->gc_time;
245 currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
247 if (task->mut_time < 0) { task->mut_time = 0; }
248 if (task->mut_etime < 0) { task->mut_etime = 0; }
253 workerTaskStop (Task *task)
255 #if defined(THREADED_RTS)
258 ASSERT(task->id == id);
259 ASSERT(myTask() == task);
264 task->stopped = rtsTrue;
267 ACQUIRE_LOCK(&sched_mutex);
268 task->next = task_free_list;
269 task_free_list = task;
270 RELEASE_LOCK(&sched_mutex);
274 resetTaskManagerAfterFork (void)
280 #if defined(THREADED_RTS)
283 startWorkerTask (Capability *cap,
284 void OSThreadProcAttr (*taskStart)(Task *task))
292 // A worker always gets a fresh Task structure.
297 // The lock here is to synchronise with taskStart(), to make sure
298 // that we have finished setting up the Task structure before the
299 // worker thread reads it.
300 ACQUIRE_LOCK(&task->lock);
304 // Give the capability directly to the worker; we can't let anyone
305 // else get in, because the new worker Task has nowhere to go to
306 // sleep so that it could be woken up again.
307 ASSERT_LOCK_HELD(&cap->lock);
308 cap->running_task = task;
310 r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
312 sysErrorBelch("failed to create OS thread");
313 stg_exit(EXIT_FAILURE);
316 debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
320 // ok, finished with the Task struct.
321 RELEASE_LOCK(&task->lock);
324 #endif /* THREADED_RTS */
328 static void *taskId(Task *task)
331 return (void *)task->id;
337 void printAllTasks(void);
343 for (task = all_tasks; task != NULL; task = task->all_link) {
344 debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
345 if (!task->stopped) {
347 debugBelch("on capability %d, ", task->cap->no);
350 debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
352 debugBelch("worker");