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 void (*setexcltask)(isc_taskmgr_t *mgr, isc_task_t *task);
119 isc_result_t (*excltask)(isc_taskmgr_t *mgr, isc_task_t **taskp);
120 } isc_taskmgrmethods_t;
122 typedef struct isc_taskmethods {
123 void (*attach)(isc_task_t *source, isc_task_t **targetp);
124 void (*detach)(isc_task_t **taskp);
125 void (*destroy)(isc_task_t **taskp);
126 void (*send)(isc_task_t *task, isc_event_t **eventp);
127 void (*sendanddetach)(isc_task_t **taskp, isc_event_t **eventp);
128 unsigned int (*unsend)(isc_task_t *task, void *sender, isc_eventtype_t type,
129 void *tag, isc_eventlist_t *events);
130 isc_result_t (*onshutdown)(isc_task_t *task, isc_taskaction_t action,
132 void (*shutdown)(isc_task_t *task);
133 void (*setname)(isc_task_t *task, const char *name, void *tag);
134 unsigned int (*purgeevents)(isc_task_t *task, void *sender,
135 isc_eventtype_t type, void *tag);
136 unsigned int (*purgerange)(isc_task_t *task, void *sender,
137 isc_eventtype_t first, isc_eventtype_t last,
139 isc_result_t (*beginexclusive)(isc_task_t *task);
140 void (*endexclusive)(isc_task_t *task);
141 void (*setprivilege)(isc_task_t *task, isc_boolean_t priv);
142 isc_boolean_t (*privilege)(isc_task_t *task);
146 * This structure is actually just the common prefix of a task manager
147 * object implementation's version of an isc_taskmgr_t.
149 * Direct use of this structure by clients is forbidden. task implementations
150 * may change the structure. 'magic' must be ISCAPI_TASKMGR_MAGIC for any
151 * of the isc_task_ routines to work. task implementations must maintain
152 * all task invariants.
155 unsigned int impmagic;
157 isc_taskmgrmethods_t *methods;
160 #define ISCAPI_TASKMGR_MAGIC ISC_MAGIC('A','t','m','g')
161 #define ISCAPI_TASKMGR_VALID(m) ((m) != NULL && \
162 (m)->magic == ISCAPI_TASKMGR_MAGIC)
165 * This is the common prefix of a task object. The same note as
166 * that for the taskmgr structure applies.
169 unsigned int impmagic;
171 isc_taskmethods_t *methods;
174 #define ISCAPI_TASK_MAGIC ISC_MAGIC('A','t','s','t')
175 #define ISCAPI_TASK_VALID(s) ((s) != NULL && \
176 (s)->magic == ISCAPI_TASK_MAGIC)
179 isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
186 *\li If 'quantum' is non-zero, then only that many events can be dispatched
187 * before the task must yield to other tasks waiting to execute. If
188 * quantum is zero, then the default quantum of the task manager will
191 *\li The 'quantum' option may be removed from isc_task_create() in the
192 * future. If this happens, isc_task_getquantum() and
193 * isc_task_setquantum() will be provided.
197 *\li 'manager' is a valid task manager.
199 *\li taskp != NULL && *taskp == NULL
203 *\li On success, '*taskp' is bound to the new task.
209 *\li #ISC_R_UNEXPECTED
210 *\li #ISC_R_SHUTTINGDOWN
214 isc_task_attach(isc_task_t *source, isc_task_t **targetp);
216 * Attach *targetp to source.
220 *\li 'source' is a valid task.
222 *\li 'targetp' points to a NULL isc_task_t *.
226 *\li *targetp is attached to source.
230 isc_task_detach(isc_task_t **taskp);
232 * Detach *taskp from its task.
236 *\li '*taskp' is a valid task.
242 *\li If '*taskp' is the last reference to the task, the task is idle (has
243 * an empty event queue), and has not been shutdown, the task will be
246 *\li If '*taskp' is the last reference to the task and
247 * the task has been shutdown,
248 * all resources used by the task will be freed.
252 isc_task_send(isc_task_t *task, isc_event_t **eventp);
254 * Send '*event' to 'task'.
258 *\li 'task' is a valid task.
259 *\li eventp != NULL && *eventp != NULL.
263 *\li *eventp == NULL.
267 isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp);
269 * Send '*event' to '*taskp' and then detach '*taskp' from its
274 *\li '*taskp' is a valid task.
275 *\li eventp != NULL && *eventp != NULL.
279 *\li *eventp == NULL.
283 *\li If '*taskp' is the last reference to the task, the task is
284 * idle (has an empty event queue), and has not been shutdown,
285 * the task will be shutdown.
287 *\li If '*taskp' is the last reference to the task and
288 * the task has been shutdown,
289 * all resources used by the task will be freed.
294 isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first,
295 isc_eventtype_t last, void *tag);
297 * Purge events from a task's event queue.
301 *\li 'task' is a valid task.
307 *\li Events in the event queue of 'task' whose sender is 'sender', whose
308 * type is >= first and <= last, and whose tag is 'tag' will be purged,
309 * unless they are marked as unpurgable.
311 *\li A sender of NULL will match any sender. A NULL tag matches any
316 *\li The number of events purged.
320 isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
323 * Purge events from a task's event queue.
327 *\li This function is equivalent to
330 * isc_task_purgerange(task, sender, type, type, tag);
335 *\li 'task' is a valid task.
339 *\li Events in the event queue of 'task' whose sender is 'sender', whose
340 * type is 'type', and whose tag is 'tag' will be purged, unless they
341 * are marked as unpurgable.
343 *\li A sender of NULL will match any sender. A NULL tag matches any
348 *\li The number of events purged.
352 isc_task_purgeevent(isc_task_t *task, isc_event_t *event);
354 * Purge 'event' from a task's event queue.
356 * XXXRTH: WARNING: This method may be removed before beta.
360 *\li If 'event' is on the task's event queue, it will be purged,
361 * unless it is marked as unpurgeable. 'event' does not have to be
362 * on the task's event queue; in fact, it can even be an invalid
363 * pointer. Purging only occurs if the event is actually on the task's
366 * \li Purging never changes the state of the task.
370 *\li 'task' is a valid task.
374 *\li 'event' is not in the event queue for 'task'.
378 *\li #ISC_TRUE The event was purged.
379 *\li #ISC_FALSE The event was not in the event queue,
380 * or was marked unpurgeable.
384 isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
385 isc_eventtype_t last, void *tag, isc_eventlist_t *events);
387 * Remove events from a task's event queue.
391 *\li 'task' is a valid task.
395 *\li *events is a valid list.
399 *\li Events in the event queue of 'task' whose sender is 'sender', whose
400 * type is >= first and <= last, and whose tag is 'tag' will be dequeued
401 * and appended to *events.
403 *\li A sender of NULL will match any sender. A NULL tag matches any
408 *\li The number of events unsent.
412 isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type,
413 void *tag, isc_eventlist_t *events);
415 * Remove events from a task's event queue.
419 *\li This function is equivalent to
422 * isc_task_unsendrange(task, sender, type, type, tag, events);
427 *\li 'task' is a valid task.
429 *\li *events is a valid list.
433 *\li Events in the event queue of 'task' whose sender is 'sender', whose
434 * type is 'type', and whose tag is 'tag' will be dequeued and appended
439 *\li The number of events unsent.
443 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action,
446 * Send a shutdown event with action 'action' and argument 'arg' when
447 * 'task' is shutdown.
451 *\li Shutdown events are posted in LIFO order.
455 *\li 'task' is a valid task.
457 *\li 'action' is a valid task action.
461 *\li When the task is shutdown, shutdown events requested with
462 * isc_task_onshutdown() will be appended to the task's event queue.
469 *\li #ISC_R_TASKSHUTTINGDOWN Task is shutting down.
473 isc_task_shutdown(isc_task_t *task);
479 *\li Shutting down a task causes any shutdown events requested with
480 * isc_task_onshutdown() to be posted (in LIFO order). The task
481 * moves into a "shutting down" mode which prevents further calls
482 * to isc_task_onshutdown().
484 *\li Trying to shutdown a task that has already been shutdown has no
489 *\li 'task' is a valid task.
493 *\li Any shutdown events requested with isc_task_onshutdown() have been
494 * posted (in LIFO order).
498 isc_task_destroy(isc_task_t **taskp);
504 *\li This call is equivalent to:
507 * isc_task_shutdown(*taskp);
508 * isc_task_detach(taskp);
513 * '*taskp' is a valid task.
517 *\li Any shutdown events requested with isc_task_onshutdown() have been
518 * posted (in LIFO order).
522 *\li If '*taskp' is the last reference to the task,
523 * all resources used by the task will be freed.
527 isc_task_setname(isc_task_t *task, const char *name, void *tag);
533 *\li Only the first 15 characters of 'name' will be copied.
535 *\li Naming a task is currently only useful for debugging purposes.
539 *\li 'task' is a valid task.
543 isc_task_getname(isc_task_t *task);
545 * Get the name of 'task', as previously set using isc_task_setname().
548 *\li This function is for debugging purposes only.
551 *\li 'task' is a valid task.
554 *\li A non-NULL pointer to a null-terminated string.
555 * If the task has not been named, the string is
561 isc_task_gettag(isc_task_t *task);
563 * Get the tag value for 'task', as previously set using isc_task_settag().
566 *\li This function is for debugging purposes only.
569 *\li 'task' is a valid task.
573 isc_task_beginexclusive(isc_task_t *task);
575 * Request exclusive access for 'task', which must be the calling
576 * task. Waits for any other concurrently executing tasks to finish their
577 * current event, and prevents any new events from executing in any of the
578 * tasks sharing a task manager with 'task'.
580 * The exclusive access must be relinquished by calling
581 * isc_task_endexclusive() before returning from the current event handler.
584 *\li 'task' is the calling task.
587 *\li #ISC_R_SUCCESS The current task now has exclusive access.
588 *\li #ISC_R_LOCKBUSY Another task has already requested exclusive
593 isc_task_endexclusive(isc_task_t *task);
595 * Relinquish the exclusive access obtained by isc_task_beginexclusive(),
596 * allowing other tasks to execute.
599 *\li 'task' is the calling task, and has obtained
600 * exclusive access by calling isc_task_spl().
604 isc_task_getcurrenttime(isc_task_t *task, isc_stdtime_t *t);
606 * Provide the most recent timestamp on the task. The timestamp is considered
607 * as the "current time" in the second-order granularity.
610 *\li 'task' is a valid task.
611 *\li 't' is a valid non NULL pointer.
614 *\li '*t' has the "current time".
618 isc_task_exiting(isc_task_t *t);
620 * Returns ISC_TRUE if the task is in the process of shutting down,
621 * ISC_FALSE otherwise.
624 *\li 'task' is a valid task.
628 isc_task_setprivilege(isc_task_t *task, isc_boolean_t priv);
630 * Set or unset the task's "privileged" flag depending on the value of
633 * Under normal circumstances this flag has no effect on the task behavior,
634 * but when the task manager has been set to privileged exeuction mode via
635 * isc_taskmgr_setmode(), only tasks with the flag set will be executed,
636 * and all other tasks will wait until they're done. Once all privileged
637 * tasks have finished executing, the task manager will automatically
638 * return to normal execution mode and nonprivileged task can resume.
641 *\li 'task' is a valid task.
645 isc_task_privilege(isc_task_t *task);
647 * Returns the current value of the task's privilege flag.
650 *\li 'task' is a valid task.
658 isc_taskmgr_createinctx(isc_mem_t *mctx, isc_appctx_t *actx,
659 unsigned int workers, unsigned int default_quantum,
660 isc_taskmgr_t **managerp);
662 isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
663 unsigned int default_quantum, isc_taskmgr_t **managerp);
665 * Create a new task manager. isc_taskmgr_createinctx() also associates
666 * the new manager with the specified application context.
670 *\li 'workers' in the number of worker threads to create. In general,
671 * the value should be close to the number of processors in the system.
672 * The 'workers' value is advisory only. An attempt will be made to
673 * create 'workers' threads, but if at least one thread creation
674 * succeeds, isc_taskmgr_create() may return ISC_R_SUCCESS.
676 *\li If 'default_quantum' is non-zero, then it will be used as the default
677 * quantum value when tasks are created. If zero, then an implementation
678 * defined default quantum will be used.
682 *\li 'mctx' is a valid memory context.
686 *\li managerp != NULL && *managerp == NULL
688 *\li 'actx' is a valid application context (for createinctx()).
692 *\li On success, '*managerp' will be attached to the newly created task
699 *\li #ISC_R_NOTHREADS No threads could be created.
700 *\li #ISC_R_UNEXPECTED An unexpected error occurred.
701 *\li #ISC_R_SHUTTINGDOWN The non-threaded, shared, task
702 * manager shutting down.
706 isc_taskmgr_setmode(isc_taskmgr_t *manager, isc_taskmgrmode_t mode);
709 isc_taskmgr_mode(isc_taskmgr_t *manager);
711 * Set/get the current operating mode of the task manager. Valid modes are:
713 *\li isc_taskmgrmode_normal
714 *\li isc_taskmgrmode_privileged
716 * In privileged execution mode, only tasks that have had the "privilege"
717 * flag set via isc_task_setprivilege() can be executed. When all such
718 * tasks are complete, the manager automatically returns to normal mode
719 * and proceeds with running non-privileged ready tasks. This means it is
720 * necessary to have at least one privileged task waiting on the ready
721 * queue *before* setting the manager into privileged execution mode,
722 * which in turn means the task which calls this function should be in
723 * task-exclusive mode when it does so.
727 *\li 'manager' is a valid task manager.
731 isc_taskmgr_destroy(isc_taskmgr_t **managerp);
733 * Destroy '*managerp'.
737 *\li Calling isc_taskmgr_destroy() will shutdown all tasks managed by
738 * *managerp that haven't already been shutdown. The call will block
739 * until all tasks have entered the done state.
741 *\li isc_taskmgr_destroy() must not be called by a task event action,
742 * because it would block forever waiting for the event action to
743 * complete. An event action that wants to cause task manager shutdown
744 * should request some non-event action thread of execution to do the
745 * shutdown, e.g. by signaling a condition variable or using
746 * isc_app_shutdown().
748 *\li Task manager references are not reference counted, so the caller
749 * must ensure that no attempt will be made to use the manager after
750 * isc_taskmgr_destroy() returns.
754 *\li '*managerp' is a valid task manager.
756 *\li isc_taskmgr_destroy() has not be called previously on '*managerp'.
760 *\li All resources used by the task manager, and any tasks it managed,
765 isc_taskmgr_setexcltask(isc_taskmgr_t *mgr, isc_task_t *task);
767 * Set a task which will be used for all task-exclusive operations.
770 *\li 'manager' is a valid task manager.
772 *\li 'task' is a valid task.
776 isc_taskmgr_excltask(isc_taskmgr_t *mgr, isc_task_t **taskp);
778 * Attach '*taskp' to the task set by isc_taskmgr_getexcltask().
779 * This task should be used whenever running in task-exclusive mode,
780 * so as to prevent deadlock between two exclusive tasks.
783 *\li 'manager' is a valid task manager.
785 *\li taskp != NULL && *taskp == NULL
792 isc_taskmgr_renderxml(isc_taskmgr_t *mgr, xmlTextWriterPtr writer);
797 * See isc_taskmgr_create() above.
800 (*isc_taskmgrcreatefunc_t)(isc_mem_t *mctx, unsigned int workers,
801 unsigned int default_quantum,
802 isc_taskmgr_t **managerp);
805 isc_task_register(isc_taskmgrcreatefunc_t createfunc);
807 * Register a new task management implementation and add it to the list of
808 * supported implementations. This function must be called when a different
809 * event library is used than the one contained in the ISC library.
813 isc__task_register(void);
815 * A short cut function that specifies the task management module in the ISC
816 * library for isc_task_register(). An application that uses the ISC library
817 * usually do not have to care about this function: it would call
818 * isc_lib_register(), which internally calls this function.
823 #endif /* ISC_TASK_H */