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 task = stgMallocBytes(sizeof(Task), "newTask");
120 task->stopped = rtsFalse;
121 task->suspended_tso = NULL;
123 task->stat = NoStatus;
126 #if defined(THREADED_RTS)
127 initCondition(&task->cond);
128 initMutex(&task->lock);
129 task->wakeup = rtsFalse;
132 #if defined(THREADED_RTS)
133 currentUserTime = getThreadCPUTime();
134 currentElapsedTime = getProcessElapsedTime();
139 task->muttimestart = currentUserTime;
140 task->elapsedtimestart = currentElapsedTime;
145 task->return_link = NULL;
147 task->all_link = all_tasks;
161 ASSERT_LOCK_HELD(&sched_mutex);
162 if (task_free_list == NULL) {
165 task = task_free_list;
166 task_free_list = task->next;
169 task->stopped = rtsFalse;
171 #if defined(THREADED_RTS)
172 task->id = osThreadId();
174 ASSERT(task->cap == NULL);
180 debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
185 boundTaskExiting (Task *task)
187 task->stopped = rtsTrue;
190 #if defined(THREADED_RTS)
191 ASSERT(osThreadId() == task->id);
193 ASSERT(myTask() == task);
194 setMyTask(task->prev_stack);
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);
204 debugTrace(DEBUG_sched, "task exiting");
208 #define TASK_ID(t) (t)->id
210 #define TASK_ID(t) (t)
214 discardTask (Task *task)
216 ASSERT_LOCK_HELD(&sched_mutex);
217 if (!task->stopped) {
218 debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
221 task->stopped = rtsTrue;
223 task->next = task_free_list;
224 task_free_list = task;
229 taskTimeStamp (Task *task USED_IF_THREADS)
231 #if defined(THREADED_RTS)
232 Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
234 currentUserTime = getThreadCPUTime();
235 currentElapsedTime = getProcessElapsedTime();
237 // XXX this is wrong; we want elapsed GC time since the
239 elapsedGCTime = stat_getElapsedGCTime();
242 currentUserTime - task->muttimestart - task->gc_time;
244 currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
246 if (task->mut_time < 0) { task->mut_time = 0; }
247 if (task->mut_etime < 0) { task->mut_etime = 0; }
252 workerTaskStop (Task *task)
254 #if defined(THREADED_RTS)
257 ASSERT(task->id == id);
258 ASSERT(myTask() == task);
263 task->stopped = rtsTrue;
266 ACQUIRE_LOCK(&sched_mutex);
267 task->next = task_free_list;
268 task_free_list = task;
269 RELEASE_LOCK(&sched_mutex);
273 resetTaskManagerAfterFork (void)
279 #if defined(THREADED_RTS)
282 startWorkerTask (Capability *cap,
283 void OSThreadProcAttr (*taskStart)(Task *task))
291 // A worker always gets a fresh Task structure.
296 // The lock here is to synchronise with taskStart(), to make sure
297 // that we have finished setting up the Task structure before the
298 // worker thread reads it.
299 ACQUIRE_LOCK(&task->lock);
303 // Give the capability directly to the worker; we can't let anyone
304 // else get in, because the new worker Task has nowhere to go to
305 // sleep so that it could be woken up again.
306 ASSERT_LOCK_HELD(&cap->lock);
307 cap->running_task = task;
309 r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
311 sysErrorBelch("failed to create OS thread");
312 stg_exit(EXIT_FAILURE);
315 debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
319 // ok, finished with the Task struct.
320 RELEASE_LOCK(&task->lock);
323 #endif /* THREADED_RTS */
327 static void *taskId(Task *task)
330 return (void *)task->id;
336 void printAllTasks(void);
342 for (task = all_tasks; task != NULL; task = task->all_link) {
343 debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
344 if (!task->stopped) {
346 debugBelch("on capability %d, ", task->cap->no);
349 debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
351 debugBelch("worker");