2 * Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1998-2001, 2003 Internet Software Consortium.
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18 /* $Id: task.h,v 1.49.206.3 2004/03/09 05:21:09 marka Exp $ */
30 * The task system provides a lightweight execution context, which is
31 * basically an event queue. When a task's event queue is non-empty, the
32 * task is runnable. A small work crew of threads, typically one per CPU,
33 * execute runnable tasks by dispatching the events on the tasks' event
34 * queues. Context switching between tasks is fast.
37 * The module ensures appropriate synchronization of data structures it
38 * creates and manipulates.
40 * The caller must ensure that isc_taskmgr_destroy() is called only
41 * once for a given manager.
44 * No anticipated impact.
50 * No anticipated impact.
61 #include <isc/eventclass.h>
63 #include <isc/stdtime.h>
64 #include <isc/types.h>
66 #define ISC_TASKEVENT_FIRSTEVENT (ISC_EVENTCLASS_TASK + 0)
67 #define ISC_TASKEVENT_SHUTDOWN (ISC_EVENTCLASS_TASK + 1)
68 #define ISC_TASKEVENT_LASTEVENT (ISC_EVENTCLASS_TASK + 65535)
77 isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
84 * If 'quantum' is non-zero, then only that many events can be dispatched
85 * before the task must yield to other tasks waiting to execute. If
86 * quantum is zero, then the default quantum of the task manager will
89 * The 'quantum' option may be removed from isc_task_create() in the
90 * future. If this happens, isc_task_getquantum() and
91 * isc_task_setquantum() will be provided.
95 * 'manager' is a valid task manager.
97 * taskp != NULL && *taskp == NULL
101 * On success, '*taskp' is bound to the new task.
112 isc_task_attach(isc_task_t *source, isc_task_t **targetp);
114 * Attach *targetp to source.
118 * 'source' is a valid task.
120 * 'targetp' points to a NULL isc_task_t *.
124 * *targetp is attached to source.
128 isc_task_detach(isc_task_t **taskp);
130 * Detach *taskp from its task.
134 * '*taskp' is a valid task.
140 * If '*taskp' is the last reference to the task, the task is idle (has
141 * an empty event queue), and has not been shutdown, the task will be
144 * If '*taskp' is the last reference to the task and
145 * the task has been shutdown,
147 * All resources used by the task will be freed.
151 isc_task_send(isc_task_t *task, isc_event_t **eventp);
153 * Send '*event' to 'task'.
157 * 'task' is a valid task.
158 * eventp != NULL && *eventp != NULL.
166 isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp);
168 * Send '*event' to '*taskp' and then detach '*taskp' from its
173 * '*taskp' is a valid task.
174 * eventp != NULL && *eventp != NULL.
182 * If '*taskp' is the last reference to the task, the task is
183 * idle (has an empty event queue), and has not been shutdown,
184 * the task will be shutdown.
186 * If '*taskp' is the last reference to the task and
187 * the task has been shutdown,
189 * All resources used by the task will be freed.
193 * Purging and Unsending
195 * Events which have been queued for a task but not delivered may be removed
196 * from the task's event queue by purging or unsending.
198 * With both types, the caller specifies a matching pattern that selects
199 * events based upon their sender, type, and tag.
201 * Purging calls isc_event_free() on the matching events.
203 * Unsending returns a list of events that matched the pattern.
204 * The caller is then responsible for them.
206 * Consumers of events should purge, not unsend.
208 * Producers of events often want to remove events when the caller indicates
209 * it is no longer interested in the object, e.g. by cancelling a timer.
210 * Sometimes this can be done by purging, but for some event types, the
211 * calls to isc_event_free() cause deadlock because the event free routine
212 * wants to acquire a lock the caller is already holding. Unsending instead
213 * of purging solves this problem. As a general rule, producers should only
214 * unsend events which they have sent.
218 isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first,
219 isc_eventtype_t last, void *tag);
221 * Purge events from a task's event queue.
225 * 'task' is a valid task.
231 * Events in the event queue of 'task' whose sender is 'sender', whose
232 * type is >= first and <= last, and whose tag is 'tag' will be purged,
233 * unless they are marked as unpurgable.
235 * A sender of NULL will match any sender. A NULL tag matches any
240 * The number of events purged.
244 isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
247 * Purge events from a task's event queue.
251 * This function is equivalent to
253 * isc_task_purgerange(task, sender, type, type, tag);
257 * 'task' is a valid task.
261 * Events in the event queue of 'task' whose sender is 'sender', whose
262 * type is 'type', and whose tag is 'tag' will be purged, unless they
263 * are marked as unpurgable.
265 * A sender of NULL will match any sender. A NULL tag matches any
270 * The number of events purged.
274 isc_task_purgeevent(isc_task_t *task, isc_event_t *event);
276 * Purge 'event' from a task's event queue.
278 * XXXRTH: WARNING: This method may be removed before beta.
282 * If 'event' is on the task's event queue, it will be purged,
283 * unless it is marked as unpurgeable. 'event' does not have to be
284 * on the task's event queue; in fact, it can even be an invalid
285 * pointer. Purging only occurs if the event is actually on the task's
288 * Purging never changes the state of the task.
292 * 'task' is a valid task.
296 * 'event' is not in the event queue for 'task'.
300 * ISC_TRUE The event was purged.
301 * ISC_FALSE The event was not in the event queue,
302 * or was marked unpurgeable.
306 isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
307 isc_eventtype_t last, void *tag, isc_eventlist_t *events);
309 * Remove events from a task's event queue.
313 * 'task' is a valid task.
317 * *events is a valid list.
321 * Events in the event queue of 'task' whose sender is 'sender', whose
322 * type is >= first and <= last, and whose tag is 'tag' will be dequeued
323 * and appended to *events.
325 * A sender of NULL will match any sender. A NULL tag matches any
330 * The number of events unsent.
334 isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type,
335 void *tag, isc_eventlist_t *events);
337 * Remove events from a task's event queue.
341 * This function is equivalent to
343 * isc_task_unsendrange(task, sender, type, type, tag, events);
347 * 'task' is a valid task.
349 * *events is a valid list.
353 * Events in the event queue of 'task' whose sender is 'sender', whose
354 * type is 'type', and whose tag is 'tag' will be dequeued and appended
359 * The number of events unsent.
363 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action,
366 * Send a shutdown event with action 'action' and argument 'arg' when
367 * 'task' is shutdown.
371 * Shutdown events are posted in LIFO order.
375 * 'task' is a valid task.
377 * 'action' is a valid task action.
381 * When the task is shutdown, shutdown events requested with
382 * isc_task_onshutdown() will be appended to the task's event queue.
389 * ISC_R_TASKSHUTTINGDOWN Task is shutting down.
393 isc_task_shutdown(isc_task_t *task);
399 * Shutting down a task causes any shutdown events requested with
400 * isc_task_onshutdown() to be posted (in LIFO order). The task
401 * moves into a "shutting down" mode which prevents further calls
402 * to isc_task_onshutdown().
404 * Trying to shutdown a task that has already been shutdown has no
409 * 'task' is a valid task.
413 * Any shutdown events requested with isc_task_onshutdown() have been
414 * posted (in LIFO order).
418 isc_task_destroy(isc_task_t **taskp);
424 * This call is equivalent to:
426 * isc_task_shutdown(*taskp);
427 * isc_task_detach(taskp);
431 * '*taskp' is a valid task.
435 * Any shutdown events requested with isc_task_onshutdown() have been
436 * posted (in LIFO order).
440 * If '*taskp' is the last reference to the task,
442 * All resources used by the task will be freed.
446 isc_task_setname(isc_task_t *task, const char *name, void *tag);
452 * Only the first 15 characters of 'name' will be copied.
454 * Naming a task is currently only useful for debugging purposes.
458 * 'task' is a valid task.
462 isc_task_getname(isc_task_t *task);
464 * Get the name of 'task', as previously set using isc_task_setname().
467 * This function is for debugging purposes only.
470 * 'task' is a valid task.
473 * A non-NULL pointer to a null-terminated string.
474 * If the task has not been named, the string is
480 isc_task_gettag(isc_task_t *task);
482 * Get the tag value for 'task', as previously set using isc_task_settag().
485 * This function is for debugging purposes only.
488 * 'task' is a valid task.
492 isc_task_beginexclusive(isc_task_t *task);
494 * Request exclusive access for 'task', which must be the calling
495 * task. Waits for any other concurrently executing tasks to finish their
496 * current event, and prevents any new events from executing in any of the
497 * tasks sharing a task manager with 'task'.
499 * The exclusive access must be relinquished by calling
500 * isc_task_endexclusive() before returning from the current event handler.
503 * 'task' is the calling task.
506 * ISC_R_SUCCESS The current task now has exclusive access.
507 * ISC_R_LOCKBUSY Another task has already requested exclusive
512 isc_task_endexclusive(isc_task_t *task);
514 * Relinquish the exclusive access obtained by isc_task_beginexclusive(),
515 * allowing other tasks to execute.
518 * 'task' is the calling task, and has obtained
519 * exclusive access by calling isc_task_spl().
523 isc_task_getcurrenttime(isc_task_t *task, isc_stdtime_t *t);
525 * Provide the most recent timestamp on the task. The timestamp is considered
526 * as the "current time" in the second-order granularity.
529 * 'task' is a valid task.
530 * 't' is a valid non NULL pointer.
533 * '*t' has the "current time".
541 isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
542 unsigned int default_quantum, isc_taskmgr_t **managerp);
544 * Create a new task manager.
548 * 'workers' in the number of worker threads to create. In general,
549 * the value should be close to the number of processors in the system.
550 * The 'workers' value is advisory only. An attempt will be made to
551 * create 'workers' threads, but if at least one thread creation
552 * succeeds, isc_taskmgr_create() may return ISC_R_SUCCESS.
554 * If 'default_quantum' is non-zero, then it will be used as the default
555 * quantum value when tasks are created. If zero, then an implementation
556 * defined default quantum will be used.
560 * 'mctx' is a valid memory context.
564 * managerp != NULL && *managerp == NULL
568 * On success, '*managerp' will be attached to the newly created task
575 * ISC_R_NOTHREADS No threads could be created.
576 * ISC_R_UNEXPECTED An unexpected error occurred.
580 isc_taskmgr_destroy(isc_taskmgr_t **managerp);
582 * Destroy '*managerp'.
586 * Calling isc_taskmgr_destroy() will shutdown all tasks managed by
587 * *managerp that haven't already been shutdown. The call will block
588 * until all tasks have entered the done state.
590 * isc_taskmgr_destroy() must not be called by a task event action,
591 * because it would block forever waiting for the event action to
592 * complete. An event action that wants to cause task manager shutdown
593 * should request some non-event action thread of execution to do the
594 * shutdown, e.g. by signalling a condition variable or using
595 * isc_app_shutdown().
597 * Task manager references are not reference counted, so the caller
598 * must ensure that no attempt will be made to use the manager after
599 * isc_taskmgr_destroy() returns.
603 * '*managerp' is a valid task manager.
605 * isc_taskmgr_destroy() has not be called previously on '*managerp'.
609 * All resources used by the task manager, and any tasks it managed,
615 #endif /* ISC_TASK_H */