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 RELEASE_LOCK(&sched_mutex);
109 #if defined(THREADED_RTS)
110 Ticks currentElapsedTime, currentUserTime;
114 task = stgMallocBytes(sizeof(Task), "newTask");
117 task->stopped = rtsFalse;
118 task->suspended_tso = NULL;
120 task->stat = NoStatus;
123 #if defined(THREADED_RTS)
124 initCondition(&task->cond);
125 initMutex(&task->lock);
126 task->wakeup = rtsFalse;
129 #if defined(THREADED_RTS)
130 currentUserTime = getThreadCPUTime();
131 currentElapsedTime = getProcessElapsedTime();
136 task->muttimestart = currentUserTime;
137 task->elapsedtimestart = currentElapsedTime;
142 task->return_link = NULL;
144 task->all_link = all_tasks;
158 ASSERT_LOCK_HELD(&sched_mutex);
159 if (task_free_list == NULL) {
162 task = task_free_list;
163 task_free_list = task->next;
166 task->stopped = rtsFalse;
168 #if defined(THREADED_RTS)
169 task->id = osThreadId();
171 ASSERT(task->cap == NULL);
177 debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
182 boundTaskExiting (Task *task)
184 task->stopped = rtsTrue;
187 #if defined(THREADED_RTS)
188 ASSERT(osThreadId() == task->id);
190 ASSERT(myTask() == task);
191 setMyTask(task->prev_stack);
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);
201 debugTrace(DEBUG_sched, "task exiting");
205 #define TASK_ID(t) (t)->id
207 #define TASK_ID(t) (t)
211 discardTask (Task *task)
213 ASSERT_LOCK_HELD(&sched_mutex);
214 if (!task->stopped) {
215 debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
218 task->stopped = rtsTrue;
220 task->next = task_free_list;
221 task_free_list = task;
226 taskTimeStamp (Task *task USED_IF_THREADS)
228 #if defined(THREADED_RTS)
229 Ticks currentElapsedTime, currentUserTime, elapsedGCTime;
231 currentUserTime = getThreadCPUTime();
232 currentElapsedTime = getProcessElapsedTime();
234 // XXX this is wrong; we want elapsed GC time since the
236 elapsedGCTime = stat_getElapsedGCTime();
239 currentUserTime - task->muttimestart - task->gc_time;
241 currentElapsedTime - task->elapsedtimestart - elapsedGCTime;
243 if (task->mut_time < 0) { task->mut_time = 0; }
244 if (task->mut_etime < 0) { task->mut_etime = 0; }
249 workerTaskStop (Task *task)
251 #if defined(THREADED_RTS)
254 ASSERT(task->id == id);
255 ASSERT(myTask() == task);
259 task->stopped = rtsTrue;
262 ACQUIRE_LOCK(&sched_mutex);
263 task->next = task_free_list;
264 task_free_list = task;
265 RELEASE_LOCK(&sched_mutex);
269 resetTaskManagerAfterFork (void)
275 #if defined(THREADED_RTS)
278 startWorkerTask (Capability *cap,
279 void OSThreadProcAttr (*taskStart)(Task *task))
287 // A worker always gets a fresh Task structure.
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);
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;
305 r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
307 sysErrorBelch("failed to create OS thread");
308 stg_exit(EXIT_FAILURE);
311 debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
315 // ok, finished with the Task struct.
316 RELEASE_LOCK(&task->lock);
319 #endif /* THREADED_RTS */
323 static void *taskId(Task *task)
326 return (void *)task->id;
332 void printAllTasks(void);
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) {
342 debugBelch("on capability %d, ", task->cap->no);
345 debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
347 debugBelch("worker");