2 * Copyright (C) 2004-2007, 2009-2012 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1998-2001, 2003 Internet Software Consortium.
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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_TEST (ISC_EVENTCLASS_TASK + 1)
92 #define ISC_TASKEVENT_LASTEVENT (ISC_EVENTCLASS_TASK + 65535)
105 isc_taskmgrmode_normal = 0,
106 isc_taskmgrmode_privileged
109 /*% Task and task manager methods */
110 typedef struct isc_taskmgrmethods {
111 void (*destroy)(isc_taskmgr_t **managerp);
112 void (*setmode)(isc_taskmgr_t *manager,
113 isc_taskmgrmode_t mode);
114 isc_taskmgrmode_t (*mode)(isc_taskmgr_t *manager);
115 isc_result_t (*taskcreate)(isc_taskmgr_t *manager,
116 unsigned int quantum,
118 } isc_taskmgrmethods_t;
120 typedef struct isc_taskmethods {
121 void (*attach)(isc_task_t *source, isc_task_t **targetp);
122 void (*detach)(isc_task_t **taskp);
123 void (*destroy)(isc_task_t **taskp);
124 void (*send)(isc_task_t *task, isc_event_t **eventp);
125 void (*sendanddetach)(isc_task_t **taskp, isc_event_t **eventp);
126 unsigned int (*unsend)(isc_task_t *task, void *sender, isc_eventtype_t type,
127 void *tag, isc_eventlist_t *events);
128 isc_result_t (*onshutdown)(isc_task_t *task, isc_taskaction_t action,
130 void (*shutdown)(isc_task_t *task);
131 void (*setname)(isc_task_t *task, const char *name, void *tag);
132 unsigned int (*purgeevents)(isc_task_t *task, void *sender,
133 isc_eventtype_t type, void *tag);
134 unsigned int (*purgerange)(isc_task_t *task, void *sender,
135 isc_eventtype_t first, isc_eventtype_t last,
137 isc_result_t (*beginexclusive)(isc_task_t *task);
138 void (*endexclusive)(isc_task_t *task);
139 void (*setprivilege)(isc_task_t *task, isc_boolean_t priv);
140 isc_boolean_t (*privilege)(isc_task_t *task);
144 * This structure is actually just the common prefix of a task manager
145 * object implementation's version of an isc_taskmgr_t.
147 * Direct use of this structure by clients is forbidden. task implementations
148 * may change the structure. 'magic' must be ISCAPI_TASKMGR_MAGIC for any
149 * of the isc_task_ routines to work. task implementations must maintain
150 * all task invariants.
153 unsigned int impmagic;
155 isc_taskmgrmethods_t *methods;
158 #define ISCAPI_TASKMGR_MAGIC ISC_MAGIC('A','t','m','g')
159 #define ISCAPI_TASKMGR_VALID(m) ((m) != NULL && \
160 (m)->magic == ISCAPI_TASKMGR_MAGIC)
163 * This is the common prefix of a task object. The same note as
164 * that for the taskmgr structure applies.
167 unsigned int impmagic;
169 isc_taskmethods_t *methods;
172 #define ISCAPI_TASK_MAGIC ISC_MAGIC('A','t','s','t')
173 #define ISCAPI_TASK_VALID(s) ((s) != NULL && \
174 (s)->magic == ISCAPI_TASK_MAGIC)
177 isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
184 *\li If 'quantum' is non-zero, then only that many events can be dispatched
185 * before the task must yield to other tasks waiting to execute. If
186 * quantum is zero, then the default quantum of the task manager will
189 *\li The 'quantum' option may be removed from isc_task_create() in the
190 * future. If this happens, isc_task_getquantum() and
191 * isc_task_setquantum() will be provided.
195 *\li 'manager' is a valid task manager.
197 *\li taskp != NULL && *taskp == NULL
201 *\li On success, '*taskp' is bound to the new task.
207 *\li #ISC_R_UNEXPECTED
208 *\li #ISC_R_SHUTTINGDOWN
212 isc_task_attach(isc_task_t *source, isc_task_t **targetp);
214 * Attach *targetp to source.
218 *\li 'source' is a valid task.
220 *\li 'targetp' points to a NULL isc_task_t *.
224 *\li *targetp is attached to source.
228 isc_task_detach(isc_task_t **taskp);
230 * Detach *taskp from its task.
234 *\li '*taskp' is a valid task.
240 *\li If '*taskp' is the last reference to the task, the task is idle (has
241 * an empty event queue), and has not been shutdown, the task will be
244 *\li If '*taskp' is the last reference to the task and
245 * the task has been shutdown,
246 * all resources used by the task will be freed.
250 isc_task_send(isc_task_t *task, isc_event_t **eventp);
252 * Send '*event' to 'task'.
256 *\li 'task' is a valid task.
257 *\li eventp != NULL && *eventp != NULL.
261 *\li *eventp == NULL.
265 isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp);
267 * Send '*event' to '*taskp' and then detach '*taskp' from its
272 *\li '*taskp' is a valid task.
273 *\li eventp != NULL && *eventp != NULL.
277 *\li *eventp == NULL.
281 *\li If '*taskp' is the last reference to the task, the task is
282 * idle (has an empty event queue), and has not been shutdown,
283 * the task will be shutdown.
285 *\li If '*taskp' is the last reference to the task and
286 * the task has been shutdown,
287 * all resources used by the task will be freed.
292 isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first,
293 isc_eventtype_t last, void *tag);
295 * Purge events from a task's event queue.
299 *\li 'task' is a valid task.
305 *\li Events in the event queue of 'task' whose sender is 'sender', whose
306 * type is >= first and <= last, and whose tag is 'tag' will be purged,
307 * unless they are marked as unpurgable.
309 *\li A sender of NULL will match any sender. A NULL tag matches any
314 *\li The number of events purged.
318 isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
321 * Purge events from a task's event queue.
325 *\li This function is equivalent to
328 * isc_task_purgerange(task, sender, type, type, tag);
333 *\li 'task' is a valid task.
337 *\li Events in the event queue of 'task' whose sender is 'sender', whose
338 * type is 'type', and whose tag is 'tag' will be purged, unless they
339 * are marked as unpurgable.
341 *\li A sender of NULL will match any sender. A NULL tag matches any
346 *\li The number of events purged.
350 isc_task_purgeevent(isc_task_t *task, isc_event_t *event);
352 * Purge 'event' from a task's event queue.
354 * XXXRTH: WARNING: This method may be removed before beta.
358 *\li If 'event' is on the task's event queue, it will be purged,
359 * unless it is marked as unpurgeable. 'event' does not have to be
360 * on the task's event queue; in fact, it can even be an invalid
361 * pointer. Purging only occurs if the event is actually on the task's
364 * \li Purging never changes the state of the task.
368 *\li 'task' is a valid task.
372 *\li 'event' is not in the event queue for 'task'.
376 *\li #ISC_TRUE The event was purged.
377 *\li #ISC_FALSE The event was not in the event queue,
378 * or was marked unpurgeable.
382 isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
383 isc_eventtype_t last, void *tag, isc_eventlist_t *events);
385 * Remove events from a task's event queue.
389 *\li 'task' is a valid task.
393 *\li *events is a valid list.
397 *\li Events in the event queue of 'task' whose sender is 'sender', whose
398 * type is >= first and <= last, and whose tag is 'tag' will be dequeued
399 * and appended to *events.
401 *\li A sender of NULL will match any sender. A NULL tag matches any
406 *\li The number of events unsent.
410 isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type,
411 void *tag, isc_eventlist_t *events);
413 * Remove events from a task's event queue.
417 *\li This function is equivalent to
420 * isc_task_unsendrange(task, sender, type, type, tag, events);
425 *\li 'task' is a valid task.
427 *\li *events is a valid list.
431 *\li Events in the event queue of 'task' whose sender is 'sender', whose
432 * type is 'type', and whose tag is 'tag' will be dequeued and appended
437 *\li The number of events unsent.
441 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action,
444 * Send a shutdown event with action 'action' and argument 'arg' when
445 * 'task' is shutdown.
449 *\li Shutdown events are posted in LIFO order.
453 *\li 'task' is a valid task.
455 *\li 'action' is a valid task action.
459 *\li When the task is shutdown, shutdown events requested with
460 * isc_task_onshutdown() will be appended to the task's event queue.
467 *\li #ISC_R_TASKSHUTTINGDOWN Task is shutting down.
471 isc_task_shutdown(isc_task_t *task);
477 *\li Shutting down a task causes any shutdown events requested with
478 * isc_task_onshutdown() to be posted (in LIFO order). The task
479 * moves into a "shutting down" mode which prevents further calls
480 * to isc_task_onshutdown().
482 *\li Trying to shutdown a task that has already been shutdown has no
487 *\li 'task' is a valid task.
491 *\li Any shutdown events requested with isc_task_onshutdown() have been
492 * posted (in LIFO order).
496 isc_task_destroy(isc_task_t **taskp);
502 *\li This call is equivalent to:
505 * isc_task_shutdown(*taskp);
506 * isc_task_detach(taskp);
511 * '*taskp' is a valid task.
515 *\li Any shutdown events requested with isc_task_onshutdown() have been
516 * posted (in LIFO order).
520 *\li If '*taskp' is the last reference to the task,
521 * all resources used by the task will be freed.
525 isc_task_setname(isc_task_t *task, const char *name, void *tag);
531 *\li Only the first 15 characters of 'name' will be copied.
533 *\li Naming a task is currently only useful for debugging purposes.
537 *\li 'task' is a valid task.
541 isc_task_getname(isc_task_t *task);
543 * Get the name of 'task', as previously set using isc_task_setname().
546 *\li This function is for debugging purposes only.
549 *\li 'task' is a valid task.
552 *\li A non-NULL pointer to a null-terminated string.
553 * If the task has not been named, the string is
559 isc_task_gettag(isc_task_t *task);
561 * Get the tag value for 'task', as previously set using isc_task_settag().
564 *\li This function is for debugging purposes only.
567 *\li 'task' is a valid task.
571 isc_task_beginexclusive(isc_task_t *task);
573 * Request exclusive access for 'task', which must be the calling
574 * task. Waits for any other concurrently executing tasks to finish their
575 * current event, and prevents any new events from executing in any of the
576 * tasks sharing a task manager with 'task'.
578 * The exclusive access must be relinquished by calling
579 * isc_task_endexclusive() before returning from the current event handler.
582 *\li 'task' is the calling task.
585 *\li #ISC_R_SUCCESS The current task now has exclusive access.
586 *\li #ISC_R_LOCKBUSY Another task has already requested exclusive
591 isc_task_endexclusive(isc_task_t *task);
593 * Relinquish the exclusive access obtained by isc_task_beginexclusive(),
594 * allowing other tasks to execute.
597 *\li 'task' is the calling task, and has obtained
598 * exclusive access by calling isc_task_spl().
602 isc_task_getcurrenttime(isc_task_t *task, isc_stdtime_t *t);
604 * Provide the most recent timestamp on the task. The timestamp is considered
605 * as the "current time" in the second-order granularity.
608 *\li 'task' is a valid task.
609 *\li 't' is a valid non NULL pointer.
612 *\li '*t' has the "current time".
616 isc_task_exiting(isc_task_t *t);
618 * Returns ISC_TRUE if the task is in the process of shutting down,
619 * ISC_FALSE otherwise.
622 *\li 'task' is a valid task.
626 isc_task_setprivilege(isc_task_t *task, isc_boolean_t priv);
628 * Set or unset the task's "privileged" flag depending on the value of
631 * Under normal circumstances this flag has no effect on the task behavior,
632 * but when the task manager has been set to privileged exeuction mode via
633 * isc_taskmgr_setmode(), only tasks with the flag set will be executed,
634 * and all other tasks will wait until they're done. Once all privileged
635 * tasks have finished executing, the task manager will automatically
636 * return to normal execution mode and nonprivileged task can resume.
639 *\li 'task' is a valid task.
643 isc_task_privilege(isc_task_t *task);
645 * Returns the current value of the task's privilege flag.
648 *\li 'task' is a valid task.
656 isc_taskmgr_createinctx(isc_mem_t *mctx, isc_appctx_t *actx,
657 unsigned int workers, unsigned int default_quantum,
658 isc_taskmgr_t **managerp);
660 isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
661 unsigned int default_quantum, isc_taskmgr_t **managerp);
663 * Create a new task manager. isc_taskmgr_createinctx() also associates
664 * the new manager with the specified application context.
668 *\li 'workers' in the number of worker threads to create. In general,
669 * the value should be close to the number of processors in the system.
670 * The 'workers' value is advisory only. An attempt will be made to
671 * create 'workers' threads, but if at least one thread creation
672 * succeeds, isc_taskmgr_create() may return ISC_R_SUCCESS.
674 *\li If 'default_quantum' is non-zero, then it will be used as the default
675 * quantum value when tasks are created. If zero, then an implementation
676 * defined default quantum will be used.
680 *\li 'mctx' is a valid memory context.
684 *\li managerp != NULL && *managerp == NULL
686 *\li 'actx' is a valid application context (for createinctx()).
690 *\li On success, '*managerp' will be attached to the newly created task
697 *\li #ISC_R_NOTHREADS No threads could be created.
698 *\li #ISC_R_UNEXPECTED An unexpected error occurred.
699 *\li #ISC_R_SHUTTINGDOWN The non-threaded, shared, task
700 * manager shutting down.
704 isc_taskmgr_setmode(isc_taskmgr_t *manager, isc_taskmgrmode_t mode);
707 isc_taskmgr_mode(isc_taskmgr_t *manager);
709 * Set/get the current operating mode of the task manager. Valid modes are:
711 *\li isc_taskmgrmode_normal
712 *\li isc_taskmgrmode_privileged
714 * In privileged execution mode, only tasks that have had the "privilege"
715 * flag set via isc_task_setprivilege() can be executed. When all such
716 * tasks are complete, the manager automatically returns to normal mode
717 * and proceeds with running non-privileged ready tasks. This means it is
718 * necessary to have at least one privileged task waiting on the ready
719 * queue *before* setting the manager into privileged execution mode,
720 * which in turn means the task which calls this function should be in
721 * task-exclusive mode when it does so.
725 *\li 'manager' is a valid task manager.
729 isc_taskmgr_destroy(isc_taskmgr_t **managerp);
731 * Destroy '*managerp'.
735 *\li Calling isc_taskmgr_destroy() will shutdown all tasks managed by
736 * *managerp that haven't already been shutdown. The call will block
737 * until all tasks have entered the done state.
739 *\li isc_taskmgr_destroy() must not be called by a task event action,
740 * because it would block forever waiting for the event action to
741 * complete. An event action that wants to cause task manager shutdown
742 * should request some non-event action thread of execution to do the
743 * shutdown, e.g. by signaling a condition variable or using
744 * isc_app_shutdown().
746 *\li Task manager references are not reference counted, so the caller
747 * must ensure that no attempt will be made to use the manager after
748 * isc_taskmgr_destroy() returns.
752 *\li '*managerp' is a valid task manager.
754 *\li isc_taskmgr_destroy() has not be called previously on '*managerp'.
758 *\li All resources used by the task manager, and any tasks it managed,
765 isc_taskmgr_renderxml(isc_taskmgr_t *mgr, xmlTextWriterPtr writer);
770 * See isc_taskmgr_create() above.
773 (*isc_taskmgrcreatefunc_t)(isc_mem_t *mctx, unsigned int workers,
774 unsigned int default_quantum,
775 isc_taskmgr_t **managerp);
778 isc_task_register(isc_taskmgrcreatefunc_t createfunc);
780 * Register a new task management implementation and add it to the list of
781 * supported implementations. This function must be called when a different
782 * event library is used than the one contained in the ISC library.
786 isc__task_register(void);
788 * A short cut function that specifies the task management module in the ISC
789 * library for isc_task_register(). An application that uses the ISC library
790 * usually do not have to care about this function: it would call
791 * isc_lib_register(), which internally calls this function.
796 #endif /* ISC_TASK_H */