/* * Copyright (C) 2004-2007, 2009 Internet Systems Consortium, Inc. ("ISC") * Copyright (C) 1998-2001, 2003 Internet Software Consortium. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. */ /* $Id: task.h,v 1.61.332.2 2009/01/18 23:47:41 tbox Exp $ */ #ifndef ISC_TASK_H #define ISC_TASK_H 1 /***** ***** Module Info *****/ /*! \file isc/task.h * \brief The task system provides a lightweight execution context, which is * basically an event queue. * When a task's event queue is non-empty, the * task is runnable. A small work crew of threads, typically one per CPU, * execute runnable tasks by dispatching the events on the tasks' event * queues. Context switching between tasks is fast. * * \li MP: * The module ensures appropriate synchronization of data structures it * creates and manipulates. * The caller must ensure that isc_taskmgr_destroy() is called only * once for a given manager. * * \li Reliability: * No anticipated impact. * * \li Resources: * TBS * * \li Security: * No anticipated impact. * * \li Standards: * None. * * \section purge Purging and Unsending * * Events which have been queued for a task but not delivered may be removed * from the task's event queue by purging or unsending. * * With both types, the caller specifies a matching pattern that selects * events based upon their sender, type, and tag. * * Purging calls isc_event_free() on the matching events. * * Unsending returns a list of events that matched the pattern. * The caller is then responsible for them. * * Consumers of events should purge, not unsend. * * Producers of events often want to remove events when the caller indicates * it is no longer interested in the object, e.g. by canceling a timer. * Sometimes this can be done by purging, but for some event types, the * calls to isc_event_free() cause deadlock because the event free routine * wants to acquire a lock the caller is already holding. Unsending instead * of purging solves this problem. As a general rule, producers should only * unsend events which they have sent. */ /*** *** Imports. ***/ #include <isc/eventclass.h> #include <isc/lang.h> #include <isc/stdtime.h> #include <isc/types.h> #include <isc/xml.h> #define ISC_TASKEVENT_FIRSTEVENT (ISC_EVENTCLASS_TASK + 0) #define ISC_TASKEVENT_SHUTDOWN (ISC_EVENTCLASS_TASK + 1) #define ISC_TASKEVENT_LASTEVENT (ISC_EVENTCLASS_TASK + 65535) /***** ***** Tasks. *****/ ISC_LANG_BEGINDECLS isc_result_t isc_task_create(isc_taskmgr_t *manager, unsigned int quantum, isc_task_t **taskp); /*%< * Create a task. * * Notes: * *\li If 'quantum' is non-zero, then only that many events can be dispatched * before the task must yield to other tasks waiting to execute. If * quantum is zero, then the default quantum of the task manager will * be used. * *\li The 'quantum' option may be removed from isc_task_create() in the * future. If this happens, isc_task_getquantum() and * isc_task_setquantum() will be provided. * * Requires: * *\li 'manager' is a valid task manager. * *\li taskp != NULL && *taskp == NULL * * Ensures: * *\li On success, '*taskp' is bound to the new task. * * Returns: * *\li #ISC_R_SUCCESS *\li #ISC_R_NOMEMORY *\li #ISC_R_UNEXPECTED *\li #ISC_R_SHUTTINGDOWN */ void isc_task_attach(isc_task_t *source, isc_task_t **targetp); /*%< * Attach *targetp to source. * * Requires: * *\li 'source' is a valid task. * *\li 'targetp' points to a NULL isc_task_t *. * * Ensures: * *\li *targetp is attached to source. */ void isc_task_detach(isc_task_t **taskp); /*%< * Detach *taskp from its task. * * Requires: * *\li '*taskp' is a valid task. * * Ensures: * *\li *taskp is NULL. * *\li If '*taskp' is the last reference to the task, the task is idle (has * an empty event queue), and has not been shutdown, the task will be * shutdown. * *\li If '*taskp' is the last reference to the task and * the task has been shutdown, * all resources used by the task will be freed. */ void isc_task_send(isc_task_t *task, isc_event_t **eventp); /*%< * Send '*event' to 'task'. * * Requires: * *\li 'task' is a valid task. *\li eventp != NULL && *eventp != NULL. * * Ensures: * *\li *eventp == NULL. */ void isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp); /*%< * Send '*event' to '*taskp' and then detach '*taskp' from its * task. * * Requires: * *\li '*taskp' is a valid task. *\li eventp != NULL && *eventp != NULL. * * Ensures: * *\li *eventp == NULL. * *\li *taskp == NULL. * *\li If '*taskp' is the last reference to the task, the task is * idle (has an empty event queue), and has not been shutdown, * the task will be shutdown. * *\li If '*taskp' is the last reference to the task and * the task has been shutdown, * all resources used by the task will be freed. */ unsigned int isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first, isc_eventtype_t last, void *tag); /*%< * Purge events from a task's event queue. * * Requires: * *\li 'task' is a valid task. * *\li last >= first * * Ensures: * *\li Events in the event queue of 'task' whose sender is 'sender', whose * type is >= first and <= last, and whose tag is 'tag' will be purged, * unless they are marked as unpurgable. * *\li A sender of NULL will match any sender. A NULL tag matches any * tag. * * Returns: * *\li The number of events purged. */ unsigned int isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type, void *tag); /*%< * Purge events from a task's event queue. * * Notes: * *\li This function is equivalent to * *\code * isc_task_purgerange(task, sender, type, type, tag); *\endcode * * Requires: * *\li 'task' is a valid task. * * Ensures: * *\li Events in the event queue of 'task' whose sender is 'sender', whose * type is 'type', and whose tag is 'tag' will be purged, unless they * are marked as unpurgable. * *\li A sender of NULL will match any sender. A NULL tag matches any * tag. * * Returns: * *\li The number of events purged. */ isc_boolean_t isc_task_purgeevent(isc_task_t *task, isc_event_t *event); /*%< * Purge 'event' from a task's event queue. * * XXXRTH: WARNING: This method may be removed before beta. * * Notes: * *\li If 'event' is on the task's event queue, it will be purged, * unless it is marked as unpurgeable. 'event' does not have to be * on the task's event queue; in fact, it can even be an invalid * pointer. Purging only occurs if the event is actually on the task's * event queue. * * \li Purging never changes the state of the task. * * Requires: * *\li 'task' is a valid task. * * Ensures: * *\li 'event' is not in the event queue for 'task'. * * Returns: * *\li #ISC_TRUE The event was purged. *\li #ISC_FALSE The event was not in the event queue, * or was marked unpurgeable. */ unsigned int isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first, isc_eventtype_t last, void *tag, isc_eventlist_t *events); /*%< * Remove events from a task's event queue. * * Requires: * *\li 'task' is a valid task. * *\li last >= first. * *\li *events is a valid list. * * Ensures: * *\li Events in the event queue of 'task' whose sender is 'sender', whose * type is >= first and <= last, and whose tag is 'tag' will be dequeued * and appended to *events. * *\li A sender of NULL will match any sender. A NULL tag matches any * tag. * * Returns: * *\li The number of events unsent. */ unsigned int isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type, void *tag, isc_eventlist_t *events); /*%< * Remove events from a task's event queue. * * Notes: * *\li This function is equivalent to * *\code * isc_task_unsendrange(task, sender, type, type, tag, events); *\endcode * * Requires: * *\li 'task' is a valid task. * *\li *events is a valid list. * * Ensures: * *\li Events in the event queue of 'task' whose sender is 'sender', whose * type is 'type', and whose tag is 'tag' will be dequeued and appended * to *events. * * Returns: * *\li The number of events unsent. */ isc_result_t isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action, const void *arg); /*%< * Send a shutdown event with action 'action' and argument 'arg' when * 'task' is shutdown. * * Notes: * *\li Shutdown events are posted in LIFO order. * * Requires: * *\li 'task' is a valid task. * *\li 'action' is a valid task action. * * Ensures: * *\li When the task is shutdown, shutdown events requested with * isc_task_onshutdown() will be appended to the task's event queue. * * Returns: * *\li #ISC_R_SUCCESS *\li #ISC_R_NOMEMORY *\li #ISC_R_TASKSHUTTINGDOWN Task is shutting down. */ void isc_task_shutdown(isc_task_t *task); /*%< * Shutdown 'task'. * * Notes: * *\li Shutting down a task causes any shutdown events requested with * isc_task_onshutdown() to be posted (in LIFO order). The task * moves into a "shutting down" mode which prevents further calls * to isc_task_onshutdown(). * *\li Trying to shutdown a task that has already been shutdown has no * effect. * * Requires: * *\li 'task' is a valid task. * * Ensures: * *\li Any shutdown events requested with isc_task_onshutdown() have been * posted (in LIFO order). */ void isc_task_destroy(isc_task_t **taskp); /*%< * Destroy '*taskp'. * * Notes: * *\li This call is equivalent to: * *\code * isc_task_shutdown(*taskp); * isc_task_detach(taskp); *\endcode * * Requires: * * '*taskp' is a valid task. * * Ensures: * *\li Any shutdown events requested with isc_task_onshutdown() have been * posted (in LIFO order). * *\li *taskp == NULL * *\li If '*taskp' is the last reference to the task, * all resources used by the task will be freed. */ void isc_task_setname(isc_task_t *task, const char *name, void *tag); /*%< * Name 'task'. * * Notes: * *\li Only the first 15 characters of 'name' will be copied. * *\li Naming a task is currently only useful for debugging purposes. * * Requires: * *\li 'task' is a valid task. */ const char * isc_task_getname(isc_task_t *task); /*%< * Get the name of 'task', as previously set using isc_task_setname(). * * Notes: *\li This function is for debugging purposes only. * * Requires: *\li 'task' is a valid task. * * Returns: *\li A non-NULL pointer to a null-terminated string. * If the task has not been named, the string is * empty. * */ void * isc_task_gettag(isc_task_t *task); /*%< * Get the tag value for 'task', as previously set using isc_task_settag(). * * Notes: *\li This function is for debugging purposes only. * * Requires: *\li 'task' is a valid task. */ isc_result_t isc_task_beginexclusive(isc_task_t *task); /*%< * Request exclusive access for 'task', which must be the calling * task. Waits for any other concurrently executing tasks to finish their * current event, and prevents any new events from executing in any of the * tasks sharing a task manager with 'task'. * * The exclusive access must be relinquished by calling * isc_task_endexclusive() before returning from the current event handler. * * Requires: *\li 'task' is the calling task. * * Returns: *\li #ISC_R_SUCCESS The current task now has exclusive access. *\li #ISC_R_LOCKBUSY Another task has already requested exclusive * access. */ void isc_task_endexclusive(isc_task_t *task); /*%< * Relinquish the exclusive access obtained by isc_task_beginexclusive(), * allowing other tasks to execute. * * Requires: *\li 'task' is the calling task, and has obtained * exclusive access by calling isc_task_spl(). */ void isc_task_getcurrenttime(isc_task_t *task, isc_stdtime_t *t); /*%< * Provide the most recent timestamp on the task. The timestamp is considered * as the "current time" in the second-order granularity. * * Requires: *\li 'task' is a valid task. *\li 't' is a valid non NULL pointer. * * Ensures: *\li '*t' has the "current time". */ /***** ***** Task Manager. *****/ isc_result_t isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers, unsigned int default_quantum, isc_taskmgr_t **managerp); /*%< * Create a new task manager. * * Notes: * *\li 'workers' in the number of worker threads to create. In general, * the value should be close to the number of processors in the system. * The 'workers' value is advisory only. An attempt will be made to * create 'workers' threads, but if at least one thread creation * succeeds, isc_taskmgr_create() may return ISC_R_SUCCESS. * *\li If 'default_quantum' is non-zero, then it will be used as the default * quantum value when tasks are created. If zero, then an implementation * defined default quantum will be used. * * Requires: * *\li 'mctx' is a valid memory context. * *\li workers > 0 * *\li managerp != NULL && *managerp == NULL * * Ensures: * *\li On success, '*managerp' will be attached to the newly created task * manager. * * Returns: * *\li #ISC_R_SUCCESS *\li #ISC_R_NOMEMORY *\li #ISC_R_NOTHREADS No threads could be created. *\li #ISC_R_UNEXPECTED An unexpected error occurred. */ void isc_taskmgr_destroy(isc_taskmgr_t **managerp); /*%< * Destroy '*managerp'. * * Notes: * *\li Calling isc_taskmgr_destroy() will shutdown all tasks managed by * *managerp that haven't already been shutdown. The call will block * until all tasks have entered the done state. * *\li isc_taskmgr_destroy() must not be called by a task event action, * because it would block forever waiting for the event action to * complete. An event action that wants to cause task manager shutdown * should request some non-event action thread of execution to do the * shutdown, e.g. by signaling a condition variable or using * isc_app_shutdown(). * *\li Task manager references are not reference counted, so the caller * must ensure that no attempt will be made to use the manager after * isc_taskmgr_destroy() returns. * * Requires: * *\li '*managerp' is a valid task manager. * *\li isc_taskmgr_destroy() has not be called previously on '*managerp'. * * Ensures: * *\li All resources used by the task manager, and any tasks it managed, * have been freed. */ #ifdef HAVE_LIBXML2 void isc_taskmgr_renderxml(isc_taskmgr_t *mgr, xmlTextWriterPtr writer); #endif ISC_LANG_ENDDECLS #endif /* ISC_TASK_H */