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18 /* $Id: task.h,v 1.69.14.2 2011-02-28 01:20:04 tbox Exp $ */
28 * \brief The task system provides a lightweight execution context, which is
29 * basically an event queue.
31 * 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.
39 * The caller must ensure that isc_taskmgr_destroy() is called only
40 * once for a given manager.
43 * No anticipated impact.
49 * No anticipated impact.
54 * \section purge Purging and Unsending
56 * Events which have been queued for a task but not delivered may be removed
57 * from the task's event queue by purging or unsending.
59 * With both types, the caller specifies a matching pattern that selects
60 * events based upon their sender, type, and tag.
62 * Purging calls isc_event_free() on the matching events.
64 * Unsending returns a list of events that matched the pattern.
65 * The caller is then responsible for them.
67 * Consumers of events should purge, not unsend.
69 * Producers of events often want to remove events when the caller indicates
70 * it is no longer interested in the object, e.g. by canceling a timer.
71 * Sometimes this can be done by purging, but for some event types, the
72 * calls to isc_event_free() cause deadlock because the event free routine
73 * wants to acquire a lock the caller is already holding. Unsending instead
74 * of purging solves this problem. As a general rule, producers should only
75 * unsend events which they have sent.
83 #include <isc/eventclass.h>
85 #include <isc/stdtime.h>
86 #include <isc/types.h>
89 #define ISC_TASKEVENT_FIRSTEVENT (ISC_EVENTCLASS_TASK + 0)
90 #define ISC_TASKEVENT_SHUTDOWN (ISC_EVENTCLASS_TASK + 1)
91 #define ISC_TASKEVENT_LASTEVENT (ISC_EVENTCLASS_TASK + 65535)
103 /*% Task and task manager methods */
104 typedef struct isc_taskmgrmethods {
105 void (*destroy)(isc_taskmgr_t **managerp);
106 isc_result_t (*taskcreate)(isc_taskmgr_t *manager,
107 unsigned int quantum,
109 } isc_taskmgrmethods_t;
111 typedef struct isc_taskmethods {
112 void (*attach)(isc_task_t *source, isc_task_t **targetp);
113 void (*detach)(isc_task_t **taskp);
114 void (*destroy)(isc_task_t **taskp);
115 void (*send)(isc_task_t *task, isc_event_t **eventp);
116 void (*sendanddetach)(isc_task_t **taskp, isc_event_t **eventp);
117 unsigned int (*unsend)(isc_task_t *task, void *sender, isc_eventtype_t type,
118 void *tag, isc_eventlist_t *events);
119 isc_result_t (*onshutdown)(isc_task_t *task, isc_taskaction_t action,
121 void (*shutdown)(isc_task_t *task);
122 void (*setname)(isc_task_t *task, const char *name, void *tag);
123 unsigned int (*purgeevents)(isc_task_t *task, void *sender,
124 isc_eventtype_t type, void *tag);
125 unsigned int (*purgerange)(isc_task_t *task, void *sender,
126 isc_eventtype_t first, isc_eventtype_t last,
128 isc_result_t (*beginexclusive)(isc_task_t *task);
129 void (*endexclusive)(isc_task_t *task);
133 * This structure is actually just the common prefix of a task manager
134 * object implementation's version of an isc_taskmgr_t.
136 * Direct use of this structure by clients is forbidden. task implementations
137 * may change the structure. 'magic' must be ISCAPI_TASKMGR_MAGIC for any
138 * of the isc_task_ routines to work. task implementations must maintain
139 * all task invariants.
142 unsigned int impmagic;
144 isc_taskmgrmethods_t *methods;
147 #define ISCAPI_TASKMGR_MAGIC ISC_MAGIC('A','t','m','g')
148 #define ISCAPI_TASKMGR_VALID(m) ((m) != NULL && \
149 (m)->magic == ISCAPI_TASKMGR_MAGIC)
152 * This is the common prefix of a task object. The same note as
153 * that for the taskmgr structure applies.
156 unsigned int impmagic;
158 isc_taskmethods_t *methods;
161 #define ISCAPI_TASK_MAGIC ISC_MAGIC('A','t','s','t')
162 #define ISCAPI_TASK_VALID(s) ((s) != NULL && \
163 (s)->magic == ISCAPI_TASK_MAGIC)
166 isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
173 *\li If 'quantum' is non-zero, then only that many events can be dispatched
174 * before the task must yield to other tasks waiting to execute. If
175 * quantum is zero, then the default quantum of the task manager will
178 *\li The 'quantum' option may be removed from isc_task_create() in the
179 * future. If this happens, isc_task_getquantum() and
180 * isc_task_setquantum() will be provided.
184 *\li 'manager' is a valid task manager.
186 *\li taskp != NULL && *taskp == NULL
190 *\li On success, '*taskp' is bound to the new task.
196 *\li #ISC_R_UNEXPECTED
197 *\li #ISC_R_SHUTTINGDOWN
201 isc_task_attach(isc_task_t *source, isc_task_t **targetp);
203 * Attach *targetp to source.
207 *\li 'source' is a valid task.
209 *\li 'targetp' points to a NULL isc_task_t *.
213 *\li *targetp is attached to source.
217 isc_task_detach(isc_task_t **taskp);
219 * Detach *taskp from its task.
223 *\li '*taskp' is a valid task.
229 *\li If '*taskp' is the last reference to the task, the task is idle (has
230 * an empty event queue), and has not been shutdown, the task will be
233 *\li If '*taskp' is the last reference to the task and
234 * the task has been shutdown,
235 * all resources used by the task will be freed.
239 isc_task_send(isc_task_t *task, isc_event_t **eventp);
241 * Send '*event' to 'task'.
245 *\li 'task' is a valid task.
246 *\li eventp != NULL && *eventp != NULL.
250 *\li *eventp == NULL.
254 isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp);
256 * Send '*event' to '*taskp' and then detach '*taskp' from its
261 *\li '*taskp' is a valid task.
262 *\li eventp != NULL && *eventp != NULL.
266 *\li *eventp == NULL.
270 *\li If '*taskp' is the last reference to the task, the task is
271 * idle (has an empty event queue), and has not been shutdown,
272 * the task will be shutdown.
274 *\li If '*taskp' is the last reference to the task and
275 * the task has been shutdown,
276 * all resources used by the task will be freed.
281 isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first,
282 isc_eventtype_t last, void *tag);
284 * Purge events from a task's event queue.
288 *\li 'task' is a valid task.
294 *\li Events in the event queue of 'task' whose sender is 'sender', whose
295 * type is >= first and <= last, and whose tag is 'tag' will be purged,
296 * unless they are marked as unpurgable.
298 *\li A sender of NULL will match any sender. A NULL tag matches any
303 *\li The number of events purged.
307 isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
310 * Purge events from a task's event queue.
314 *\li This function is equivalent to
317 * isc_task_purgerange(task, sender, type, type, tag);
322 *\li 'task' is a valid task.
326 *\li Events in the event queue of 'task' whose sender is 'sender', whose
327 * type is 'type', and whose tag is 'tag' will be purged, unless they
328 * are marked as unpurgable.
330 *\li A sender of NULL will match any sender. A NULL tag matches any
335 *\li The number of events purged.
339 isc_task_purgeevent(isc_task_t *task, isc_event_t *event);
341 * Purge 'event' from a task's event queue.
343 * XXXRTH: WARNING: This method may be removed before beta.
347 *\li If 'event' is on the task's event queue, it will be purged,
348 * unless it is marked as unpurgeable. 'event' does not have to be
349 * on the task's event queue; in fact, it can even be an invalid
350 * pointer. Purging only occurs if the event is actually on the task's
353 * \li Purging never changes the state of the task.
357 *\li 'task' is a valid task.
361 *\li 'event' is not in the event queue for 'task'.
365 *\li #ISC_TRUE The event was purged.
366 *\li #ISC_FALSE The event was not in the event queue,
367 * or was marked unpurgeable.
371 isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
372 isc_eventtype_t last, void *tag, isc_eventlist_t *events);
374 * Remove events from a task's event queue.
378 *\li 'task' is a valid task.
382 *\li *events is a valid list.
386 *\li Events in the event queue of 'task' whose sender is 'sender', whose
387 * type is >= first and <= last, and whose tag is 'tag' will be dequeued
388 * and appended to *events.
390 *\li A sender of NULL will match any sender. A NULL tag matches any
395 *\li The number of events unsent.
399 isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type,
400 void *tag, isc_eventlist_t *events);
402 * Remove events from a task's event queue.
406 *\li This function is equivalent to
409 * isc_task_unsendrange(task, sender, type, type, tag, events);
414 *\li 'task' is a valid task.
416 *\li *events is a valid list.
420 *\li Events in the event queue of 'task' whose sender is 'sender', whose
421 * type is 'type', and whose tag is 'tag' will be dequeued and appended
426 *\li The number of events unsent.
430 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action,
433 * Send a shutdown event with action 'action' and argument 'arg' when
434 * 'task' is shutdown.
438 *\li Shutdown events are posted in LIFO order.
442 *\li 'task' is a valid task.
444 *\li 'action' is a valid task action.
448 *\li When the task is shutdown, shutdown events requested with
449 * isc_task_onshutdown() will be appended to the task's event queue.
456 *\li #ISC_R_TASKSHUTTINGDOWN Task is shutting down.
460 isc_task_shutdown(isc_task_t *task);
466 *\li Shutting down a task causes any shutdown events requested with
467 * isc_task_onshutdown() to be posted (in LIFO order). The task
468 * moves into a "shutting down" mode which prevents further calls
469 * to isc_task_onshutdown().
471 *\li Trying to shutdown a task that has already been shutdown has no
476 *\li 'task' is a valid task.
480 *\li Any shutdown events requested with isc_task_onshutdown() have been
481 * posted (in LIFO order).
485 isc_task_destroy(isc_task_t **taskp);
491 *\li This call is equivalent to:
494 * isc_task_shutdown(*taskp);
495 * isc_task_detach(taskp);
500 * '*taskp' is a valid task.
504 *\li Any shutdown events requested with isc_task_onshutdown() have been
505 * posted (in LIFO order).
509 *\li If '*taskp' is the last reference to the task,
510 * all resources used by the task will be freed.
514 isc_task_setname(isc_task_t *task, const char *name, void *tag);
520 *\li Only the first 15 characters of 'name' will be copied.
522 *\li Naming a task is currently only useful for debugging purposes.
526 *\li 'task' is a valid task.
530 isc_task_getname(isc_task_t *task);
532 * Get the name of 'task', as previously set using isc_task_setname().
535 *\li This function is for debugging purposes only.
538 *\li 'task' is a valid task.
541 *\li A non-NULL pointer to a null-terminated string.
542 * If the task has not been named, the string is
548 isc_task_gettag(isc_task_t *task);
550 * Get the tag value for 'task', as previously set using isc_task_settag().
553 *\li This function is for debugging purposes only.
556 *\li 'task' is a valid task.
560 isc_task_beginexclusive(isc_task_t *task);
562 * Request exclusive access for 'task', which must be the calling
563 * task. Waits for any other concurrently executing tasks to finish their
564 * current event, and prevents any new events from executing in any of the
565 * tasks sharing a task manager with 'task'.
567 * The exclusive access must be relinquished by calling
568 * isc_task_endexclusive() before returning from the current event handler.
571 *\li 'task' is the calling task.
574 *\li #ISC_R_SUCCESS The current task now has exclusive access.
575 *\li #ISC_R_LOCKBUSY Another task has already requested exclusive
580 isc_task_endexclusive(isc_task_t *task);
582 * Relinquish the exclusive access obtained by isc_task_beginexclusive(),
583 * allowing other tasks to execute.
586 *\li 'task' is the calling task, and has obtained
587 * exclusive access by calling isc_task_spl().
591 isc_task_getcurrenttime(isc_task_t *task, isc_stdtime_t *t);
593 * Provide the most recent timestamp on the task. The timestamp is considered
594 * as the "current time" in the second-order granularity.
597 *\li 'task' is a valid task.
598 *\li 't' is a valid non NULL pointer.
601 *\li '*t' has the "current time".
605 isc_task_exiting(isc_task_t *t);
607 * Returns ISC_TRUE if the task is in the process of shutting down,
608 * ISC_FALSE otherwise.
611 *\li 'task' is a valid task.
619 isc_taskmgr_createinctx(isc_mem_t *mctx, isc_appctx_t *actx,
620 unsigned int workers, unsigned int default_quantum,
621 isc_taskmgr_t **managerp);
623 isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
624 unsigned int default_quantum, isc_taskmgr_t **managerp);
626 * Create a new task manager. isc_taskmgr_createinctx() also associates
627 * the new manager with the specified application context.
631 *\li 'workers' in the number of worker threads to create. In general,
632 * the value should be close to the number of processors in the system.
633 * The 'workers' value is advisory only. An attempt will be made to
634 * create 'workers' threads, but if at least one thread creation
635 * succeeds, isc_taskmgr_create() may return ISC_R_SUCCESS.
637 *\li If 'default_quantum' is non-zero, then it will be used as the default
638 * quantum value when tasks are created. If zero, then an implementation
639 * defined default quantum will be used.
643 *\li 'mctx' is a valid memory context.
647 *\li managerp != NULL && *managerp == NULL
649 *\li 'actx' is a valid application context (for createinctx()).
653 *\li On success, '*managerp' will be attached to the newly created task
660 *\li #ISC_R_NOTHREADS No threads could be created.
661 *\li #ISC_R_UNEXPECTED An unexpected error occurred.
662 *\li #ISC_R_SHUTTINGDOWN The non-threaded, shared, task
663 * manager shutting down.
667 isc_taskmgr_destroy(isc_taskmgr_t **managerp);
669 * Destroy '*managerp'.
673 *\li Calling isc_taskmgr_destroy() will shutdown all tasks managed by
674 * *managerp that haven't already been shutdown. The call will block
675 * until all tasks have entered the done state.
677 *\li isc_taskmgr_destroy() must not be called by a task event action,
678 * because it would block forever waiting for the event action to
679 * complete. An event action that wants to cause task manager shutdown
680 * should request some non-event action thread of execution to do the
681 * shutdown, e.g. by signaling a condition variable or using
682 * isc_app_shutdown().
684 *\li Task manager references are not reference counted, so the caller
685 * must ensure that no attempt will be made to use the manager after
686 * isc_taskmgr_destroy() returns.
690 *\li '*managerp' is a valid task manager.
692 *\li isc_taskmgr_destroy() has not be called previously on '*managerp'.
696 *\li All resources used by the task manager, and any tasks it managed,
703 isc_taskmgr_renderxml(isc_taskmgr_t *mgr, xmlTextWriterPtr writer);
708 * See isc_taskmgr_create() above.
711 (*isc_taskmgrcreatefunc_t)(isc_mem_t *mctx, unsigned int workers,
712 unsigned int default_quantum,
713 isc_taskmgr_t **managerp);
716 isc_task_register(isc_taskmgrcreatefunc_t createfunc);
718 * Register a new task management implementation and add it to the list of
719 * supported implementations. This function must be called when a different
720 * event library is used than the one contained in the ISC library.
724 isc__task_register(void);
726 * A short cut function that specifies the task management module in the ISC
727 * library for isc_task_register(). An application that uses the ISC library
728 * usually do not have to care about this function: it would call
729 * isc_lib_register(), which internally calls this function.
734 #endif /* ISC_TASK_H */