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);
68 freeTaskManager (void)
72 ASSERT_LOCK_HELD(&sched_mutex);
74 debugTrace(DEBUG_sched, "freeing task manager, %d tasks still running",
77 for (task = all_tasks; task != NULL; task = next) {
78 next = task->all_link;
80 // We only free resources if the Task is not in use. A
81 // Task may still be in use if we have a Haskell thread in
82 // a foreign call while we are attempting to shut down the
84 #if defined(THREADED_RTS)
85 closeCondition(&task->cond);
86 closeMutex(&task->lock);
92 task_free_list = NULL;
93 #if defined(THREADED_RTS)
94 freeThreadLocalKey(¤tTaskKey);
104 #if defined(THREADED_RTS)
105 Ticks currentElapsedTime, currentUserTime;
109 #define ROUND_TO_CACHE_LINE(x) ((((x)+63) / 64) * 64)
110 task = stgMallocBytes(ROUND_TO_CACHE_LINE(sizeof(Task)), "newTask");
113 task->stopped = rtsFalse;
114 task->suspended_tso = NULL;
116 task->stat = NoStatus;
119 #if defined(THREADED_RTS)
120 initCondition(&task->cond);
121 initMutex(&task->lock);
122 task->wakeup = rtsFalse;
125 #if defined(THREADED_RTS)
126 currentUserTime = getThreadCPUTime();
127 currentElapsedTime = getProcessElapsedTime();
132 task->muttimestart = currentUserTime;
133 task->elapsedtimestart = currentElapsedTime;
138 task->return_link = NULL;
140 task->all_link = all_tasks;
153 ASSERT_LOCK_HELD(&sched_mutex);
154 if (task_free_list == NULL) {
157 task = task_free_list;
158 task_free_list = task->next;
161 task->stopped = rtsFalse;
163 #if defined(THREADED_RTS)
164 task->id = osThreadId();
166 ASSERT(task->cap == NULL);
172 debugTrace(DEBUG_sched, "new task (taskCount: %d)", taskCount);
177 boundTaskExiting (Task *task)
180 task->stopped = rtsTrue;
183 #if defined(THREADED_RTS)
184 ASSERT(osThreadId() == task->id);
186 ASSERT(myTask() == task);
187 setMyTask(task->prev_stack);
191 // sadly, we need a lock around the free task list. Todo: eliminate.
192 ACQUIRE_LOCK(&sched_mutex);
193 task->next = task_free_list;
194 task_free_list = task;
195 RELEASE_LOCK(&sched_mutex);
197 debugTrace(DEBUG_sched, "task exiting");
201 #define TASK_ID(t) (t)->id
203 #define TASK_ID(t) (t)
207 discardTask (Task *task)
209 ASSERT_LOCK_HELD(&sched_mutex);
210 if (!task->stopped) {
211 debugTrace(DEBUG_sched, "discarding task %ld", (long)TASK_ID(task));
213 if (task->tso == NULL) {
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);
260 task->stopped = rtsTrue;
264 ACQUIRE_LOCK(&sched_mutex);
265 task->next = task_free_list;
266 task_free_list = task;
267 RELEASE_LOCK(&sched_mutex);
271 resetTaskManagerAfterFork (void)
277 #if defined(THREADED_RTS)
280 startWorkerTask (Capability *cap,
281 void OSThreadProcAttr (*taskStart)(Task *task))
289 // A worker always gets a fresh Task structure.
294 // The lock here is to synchronise with taskStart(), to make sure
295 // that we have finished setting up the Task structure before the
296 // worker thread reads it.
297 ACQUIRE_LOCK(&task->lock);
301 // Give the capability directly to the worker; we can't let anyone
302 // else get in, because the new worker Task has nowhere to go to
303 // sleep so that it could be woken up again.
304 ASSERT_LOCK_HELD(&cap->lock);
305 cap->running_task = task;
307 r = createOSThread(&tid, (OSThreadProc *)taskStart, task);
309 sysErrorBelch("failed to create OS thread");
310 stg_exit(EXIT_FAILURE);
313 debugTrace(DEBUG_sched, "new worker task (taskCount: %d)", taskCount);
317 // ok, finished with the Task struct.
318 RELEASE_LOCK(&task->lock);
321 #endif /* THREADED_RTS */
325 static void *taskId(Task *task)
328 return (void *)task->id;
334 void printAllTasks(void);
340 for (task = all_tasks; task != NULL; task = task->all_link) {
341 debugBelch("task %p is %s, ", taskId(task), task->stopped ? "stopped" : "alive");
342 if (!task->stopped) {
344 debugBelch("on capability %d, ", task->cap->no);
347 debugBelch("bound to thread %lu", (unsigned long)task->tso->id);
349 debugBelch("worker");