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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#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 <stdbool.h>
#include <isc/eventclass.h>
#include <isc/json.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_TEST (ISC_EVENTCLASS_TASK + 1)
#define ISC_TASKEVENT_LASTEVENT (ISC_EVENTCLASS_TASK + 65535)
/*****
***** Tasks.
*****/
ISC_LANG_BEGINDECLS
/***
*** Types
***/
typedef enum {
isc_taskqueue_normal = 0,
isc_taskqueue_slow = 1,
} isc_taskqueue_t;
#define ISC_TASK_QUANTUM_SLOW 1024
typedef enum {
isc_taskmgrmode_normal = 0,
isc_taskmgrmode_privileged
} isc_taskmgrmode_t;
/*% Task and task manager methods */
typedef struct isc_taskmgrmethods {
void (*destroy)(isc_taskmgr_t **managerp);
void (*setmode)(isc_taskmgr_t *manager,
isc_taskmgrmode_t mode);
isc_taskmgrmode_t (*mode)(isc_taskmgr_t *manager);
isc_result_t (*taskcreate)(isc_taskmgr_t *manager,
unsigned int quantum,
isc_task_t **taskp);
void (*setexcltask)(isc_taskmgr_t *mgr, isc_task_t *task);
isc_result_t (*excltask)(isc_taskmgr_t *mgr, isc_task_t **taskp);
} isc_taskmgrmethods_t;
typedef struct isc_taskmethods {
void (*attach)(isc_task_t *source, isc_task_t **targetp);
void (*detach)(isc_task_t **taskp);
void (*destroy)(isc_task_t **taskp);
void (*send)(isc_task_t *task, isc_event_t **eventp);
void (*sendanddetach)(isc_task_t **taskp, isc_event_t **eventp);
unsigned int (*unsend)(isc_task_t *task, void *sender, isc_eventtype_t type,
void *tag, isc_eventlist_t *events);
isc_result_t (*onshutdown)(isc_task_t *task, isc_taskaction_t action,
void *arg);
void (*shutdown)(isc_task_t *task);
void (*setname)(isc_task_t *task, const char *name, void *tag);
unsigned int (*purgeevents)(isc_task_t *task, void *sender,
isc_eventtype_t type, void *tag);
unsigned int (*purgerange)(isc_task_t *task, void *sender,
isc_eventtype_t first, isc_eventtype_t last,
void *tag);
isc_result_t (*beginexclusive)(isc_task_t *task);
void (*endexclusive)(isc_task_t *task);
void (*setprivilege)(isc_task_t *task, bool priv);
bool (*privilege)(isc_task_t *task);
} isc_taskmethods_t;
/*%
* This structure is actually just the common prefix of a task manager
* object implementation's version of an isc_taskmgr_t.
* \brief
* Direct use of this structure by clients is forbidden. task implementations
* may change the structure. 'magic' must be ISCAPI_TASKMGR_MAGIC for any
* of the isc_task_ routines to work. task implementations must maintain
* all task invariants.
*/
struct isc_taskmgr {
unsigned int impmagic;
unsigned int magic;
isc_taskmgrmethods_t *methods;
};
#define ISCAPI_TASKMGR_MAGIC ISC_MAGIC('A','t','m','g')
#define ISCAPI_TASKMGR_VALID(m) ((m) != NULL && \
(m)->magic == ISCAPI_TASKMGR_MAGIC)
/*%
* This is the common prefix of a task object. The same note as
* that for the taskmgr structure applies.
*/
struct isc_task {
unsigned int impmagic;
unsigned int magic;
isc_taskmethods_t *methods;
};
#define ISCAPI_TASK_MAGIC ISC_MAGIC('A','t','s','t')
#define ISCAPI_TASK_VALID(s) ((s) != NULL && \
(s)->magic == ISCAPI_TASK_MAGIC)
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.
*/
bool
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 #true The event was purged.
*\li #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,
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_SHUTTINGDOWN 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);
void
isc_task_getcurrenttimex(isc_task_t *task, isc_time_t *t);
/*%<
* Provide the most recent timestamp on the task. The timestamp is considered
* as the "current time".
*
* isc_task_getcurrentime() returns the time in one-second granularity;
* isc_task_getcurrentimex() returns it in nanosecond granularity.
*
* Requires:
*\li 'task' is a valid task.
*\li 't' is a valid non NULL pointer.
*
* Ensures:
*\li '*t' has the "current time".
*/
bool
isc_task_exiting(isc_task_t *t);
/*%<
* Returns true if the task is in the process of shutting down,
* false otherwise.
*
* Requires:
*\li 'task' is a valid task.
*/
void
isc_task_setprivilege(isc_task_t *task, bool priv);
/*%<
* Set or unset the task's "privileged" flag depending on the value of
* 'priv'.
*
* Under normal circumstances this flag has no effect on the task behavior,
* but when the task manager has been set to privileged execution mode via
* isc_taskmgr_setmode(), only tasks with the flag set will be executed,
* and all other tasks will wait until they're done. Once all privileged
* tasks have finished executing, the task manager will automatically
* return to normal execution mode and nonprivileged task can resume.
*
* Requires:
*\li 'task' is a valid task.
*/
bool
isc_task_privilege(isc_task_t *task);
/*%<
* Returns the current value of the task's privilege flag.
*
* Requires:
*\li 'task' is a valid task.
*/
/*****
***** Task Manager.
*****/
isc_result_t
isc_taskmgr_createinctx(isc_mem_t *mctx, isc_appctx_t *actx,
unsigned int workers, unsigned int default_quantum,
isc_taskmgr_t **managerp);
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. isc_taskmgr_createinctx() also associates
* the new manager with the specified application context.
*
* 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
*
*\li 'actx' is a valid application context (for createinctx()).
*
* 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.
*\li #ISC_R_SHUTTINGDOWN The non-threaded, shared, task
* manager shutting down.
*/
void
isc_taskmgr_setmode(isc_taskmgr_t *manager, isc_taskmgrmode_t mode);
isc_taskmgrmode_t
isc_taskmgr_mode(isc_taskmgr_t *manager);
/*%<
* Set/get the current operating mode of the task manager. Valid modes are:
*
*\li isc_taskmgrmode_normal
*\li isc_taskmgrmode_privileged
*
* In privileged execution mode, only tasks that have had the "privilege"
* flag set via isc_task_setprivilege() can be executed. When all such
* tasks are complete, the manager automatically returns to normal mode
* and proceeds with running non-privileged ready tasks. This means it is
* necessary to have at least one privileged task waiting on the ready
* queue *before* setting the manager into privileged execution mode,
* which in turn means the task which calls this function should be in
* task-exclusive mode when it does so.
*
* Requires:
*
*\li 'manager' is a valid task manager.
*/
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.
*/
void
isc_taskmgr_setexcltask(isc_taskmgr_t *mgr, isc_task_t *task);
/*%<
* Set a task which will be used for all task-exclusive operations.
*
* Requires:
*\li 'manager' is a valid task manager.
*
*\li 'task' is a valid task.
*/
isc_result_t
isc_taskmgr_excltask(isc_taskmgr_t *mgr, isc_task_t **taskp);
/*%<
* Attach '*taskp' to the task set by isc_taskmgr_getexcltask().
* This task should be used whenever running in task-exclusive mode,
* so as to prevent deadlock between two exclusive tasks.
*
* Requires:
*\li 'manager' is a valid task manager.
*\li taskp != NULL && *taskp == NULL
*/
#ifdef HAVE_LIBXML2
int
isc_taskmgr_renderxml(isc_taskmgr_t *mgr, xmlTextWriterPtr writer);
#endif
#ifdef HAVE_JSON
isc_result_t
isc_taskmgr_renderjson(isc_taskmgr_t *mgr, json_object *tasksobj);
#endif
/*%<
* See isc_taskmgr_create() above.
*/
typedef isc_result_t
(*isc_taskmgrcreatefunc_t)(isc_mem_t *mctx, unsigned int workers,
unsigned int default_quantum,
isc_taskmgr_t **managerp);
isc_result_t
isc_task_register(isc_taskmgrcreatefunc_t createfunc);
/*%<
* Register a new task management implementation and add it to the list of
* supported implementations. This function must be called when a different
* event library is used than the one contained in the ISC library.
*/
isc_result_t
isc__task_register(void);
/*%<
* A short cut function that specifies the task management module in the ISC
* library for isc_task_register(). An application that uses the ISC library
* usually do not have to care about this function: it would call
* isc_lib_register(), which internally calls this function.
*/
ISC_LANG_ENDDECLS
#endif /* ISC_TASK_H */