task.c

bind 9.3结合mysql数据库

					}
					dispatch_count++;
#ifndef ISC_PLATFORM_USETHREADS
					total_dispatch_count++;
#endif /* ISC_PLATFORM_USETHREADS */
				}

				if (task->references == 0 &&
				    EMPTY(task->events) &&
				    !TASK_SHUTTINGDOWN(task)) {
					isc_boolean_t was_idle;

					/*
					 * There are no references and no
					 * pending events for this task,
					 * which means it will not become
					 * runnable again via an external
					 * action (such as sending an event
					 * or detaching).
					 *
					 * We initiate shutdown to prevent
					 * it from becoming a zombie.
					 *
					 * We do this here instead of in
					 * the "if EMPTY(task->events)" block
					 * below because:
					 *
					 *	If we post no shutdown events,
					 *	we want the task to finish.
					 *
					 *	If we did post shutdown events,
					 *	will still want the task's
					 *	quantum to be applied.
					 */
					was_idle = task_shutdown(task);
					INSIST(!was_idle);
				}

				if (EMPTY(task->events)) {
					/*
					 * Nothing else to do for this task
					 * right now.
					 */
					XTRACE(isc_msgcat_get(isc_msgcat,
							      ISC_MSGSET_TASK,
							      ISC_MSG_EMPTY,
							      "empty"));
					if (task->references == 0 &&
					    TASK_SHUTTINGDOWN(task)) {
						/*
						 * The task is done.
						 */
						XTRACE(isc_msgcat_get(
							       isc_msgcat,
							       ISC_MSGSET_TASK,
							       ISC_MSG_DONE,
							       "done"));
						finished = ISC_TRUE;
						task->state = task_state_done;
					} else
						task->state = task_state_idle;
					done = ISC_TRUE;
				} else if (dispatch_count >= task->quantum) {
					/*
					 * Our quantum has expired, but
					 * there is more work to be done.
					 * We'll requeue it to the ready
					 * queue later.
					 *
					 * We don't check quantum until
					 * dispatching at least one event,
					 * so the minimum quantum is one.
					 */
					XTRACE(isc_msgcat_get(isc_msgcat,
							      ISC_MSGSET_TASK,
							      ISC_MSG_QUANTUM,
							      "quantum"));
					task->state = task_state_ready;
					requeue = ISC_TRUE;
					done = ISC_TRUE;
				}
			} while (!done);
			UNLOCK(&task->lock);

			if (finished)
				task_finished(task);

			LOCK(&manager->lock);
			manager->tasks_running--;
#ifdef ISC_PLATFORM_USETHREADS
			if (manager->exclusive_requested &&
			    manager->tasks_running == 1) {
				SIGNAL(&manager->exclusive_granted);
			}
#endif /* ISC_PLATFORM_USETHREADS */
			if (requeue) {
				/*
				 * We know we're awake, so we don't have
				 * to wakeup any sleeping threads if the
				 * ready queue is empty before we requeue.
				 *
				 * A possible optimization if the queue is
				 * empty is to 'goto' the 'if (task != NULL)'
				 * block, avoiding the ENQUEUE of the task
				 * and the subsequent immediate DEQUEUE
				 * (since it is the only executable task).
				 * We don't do this because then we'd be
				 * skipping the exit_requested check.  The
				 * cost of ENQUEUE is low anyway, especially
				 * when you consider that we'd have to do
				 * an extra EMPTY check to see if we could
				 * do the optimization.  If the ready queue
				 * were usually nonempty, the 'optimization'
				 * might even hurt rather than help.
				 */
#ifdef ISC_PLATFORM_USETHREADS
				ENQUEUE(manager->ready_tasks, task,
					ready_link);
#else
				ENQUEUE(ready_tasks, task, ready_link);
#endif
			}
		}
	}
#ifndef ISC_PLATFORM_USETHREADS
	ISC_LIST_APPENDLIST(manager->ready_tasks, ready_tasks, ready_link);
#endif
	UNLOCK(&manager->lock);
}

#ifdef ISC_PLATFORM_USETHREADS
static isc_threadresult_t
#ifdef _WIN32
WINAPI
#endif
run(void *uap) {
	isc_taskmgr_t *manager = uap;

	XTHREADTRACE(isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
				    ISC_MSG_STARTING, "starting"));

	dispatch(manager);

	XTHREADTRACE(isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
				    ISC_MSG_EXITING, "exiting"));

	return ((isc_threadresult_t)0);
}
#endif /* ISC_PLATFORM_USETHREADS */

static void
manager_free(isc_taskmgr_t *manager) {
	isc_mem_t *mctx;

#ifdef ISC_PLATFORM_USETHREADS
	(void)isc_condition_destroy(&manager->exclusive_granted);	
	(void)isc_condition_destroy(&manager->work_available);
	isc_mem_put(manager->mctx, manager->threads,
		    manager->workers * sizeof(isc_thread_t));
#endif /* ISC_PLATFORM_USETHREADS */
	DESTROYLOCK(&manager->lock);
	manager->magic = 0;
	mctx = manager->mctx;
	isc_mem_put(mctx, manager, sizeof(*manager));
	isc_mem_detach(&mctx);
}

isc_result_t
isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
		   unsigned int default_quantum, isc_taskmgr_t **managerp)
{
	isc_result_t result;
	unsigned int i, started = 0;
	isc_taskmgr_t *manager;

	/*
	 * Create a new task manager.
	 */

	REQUIRE(workers > 0);
	REQUIRE(managerp != NULL && *managerp == NULL);

#ifndef ISC_PLATFORM_USETHREADS
	UNUSED(i);
	UNUSED(started);
	UNUSED(workers);

	if (taskmgr != NULL) {
		taskmgr->refs++;
		*managerp = taskmgr;
		return (ISC_R_SUCCESS);
	}
#endif /* ISC_PLATFORM_USETHREADS */

	manager = isc_mem_get(mctx, sizeof(*manager));
	if (manager == NULL)
		return (ISC_R_NOMEMORY);
	manager->magic = TASK_MANAGER_MAGIC;
	manager->mctx = NULL;
	manager->workers = 0;
	if (isc_mutex_init(&manager->lock) != ISC_R_SUCCESS) {
		UNEXPECTED_ERROR(__FILE__, __LINE__,
				 "isc_mutex_init() %s",
				 isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
						ISC_MSG_FAILED, "failed"));
		result = ISC_R_UNEXPECTED;
		goto cleanup_mgr;
	}
#ifdef ISC_PLATFORM_USETHREADS
	manager->threads = isc_mem_get(mctx, workers * sizeof(isc_thread_t));
	if (manager->threads == NULL) {
		result = ISC_R_NOMEMORY;
		goto cleanup_lock;
	}
	if (isc_condition_init(&manager->work_available) != ISC_R_SUCCESS) {
		UNEXPECTED_ERROR(__FILE__, __LINE__,
				 "isc_condition_init() %s",
				 isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
						ISC_MSG_FAILED, "failed"));
		result = ISC_R_UNEXPECTED;
		goto cleanup_threads;
	}
	if (isc_condition_init(&manager->exclusive_granted) != ISC_R_SUCCESS) {
		UNEXPECTED_ERROR(__FILE__, __LINE__,
				 "isc_condition_init() %s",
				 isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
						ISC_MSG_FAILED, "failed"));
		result = ISC_R_UNEXPECTED;
		goto cleanup_workavailable;
	}
#endif /* ISC_PLATFORM_USETHREADS */
	if (default_quantum == 0)
		default_quantum = DEFAULT_DEFAULT_QUANTUM;
	manager->default_quantum = default_quantum;
	INIT_LIST(manager->tasks);
	INIT_LIST(manager->ready_tasks);
	manager->tasks_running = 0;
	manager->exclusive_requested = ISC_FALSE;
	manager->exiting = ISC_FALSE;
	manager->workers = 0;

	isc_mem_attach(mctx, &manager->mctx);

#ifdef ISC_PLATFORM_USETHREADS
	LOCK(&manager->lock);
	/*
	 * Start workers.
	 */
	for (i = 0; i < workers; i++) {
		if (isc_thread_create(run, manager,
				      &manager->threads[manager->workers]) ==
		    ISC_R_SUCCESS) {
			manager->workers++;
			started++;
		}
	}
	UNLOCK(&manager->lock);

	if (started == 0) {
		manager_free(manager);
		return (ISC_R_NOTHREADS);
	}
	isc_thread_setconcurrency(workers);
#else /* ISC_PLATFORM_USETHREADS */
	manager->refs = 1;
	taskmgr = manager;
#endif /* ISC_PLATFORM_USETHREADS */

	*managerp = manager;

	return (ISC_R_SUCCESS);

#ifdef ISC_PLATFORM_USETHREADS
 cleanup_workavailable:
	(void)isc_condition_destroy(&manager->work_available);
 cleanup_threads:
	isc_mem_put(mctx, manager->threads, workers * sizeof(isc_thread_t));
 cleanup_lock:
	DESTROYLOCK(&manager->lock);
#endif
 cleanup_mgr:
	isc_mem_put(mctx, manager, sizeof(*manager));
	return (result);
}

void
isc_taskmgr_destroy(isc_taskmgr_t **managerp) {
	isc_taskmgr_t *manager;
	isc_task_t *task;
	unsigned int i;

	/*
	 * Destroy '*managerp'.
	 */

	REQUIRE(managerp != NULL);
	manager = *managerp;
	REQUIRE(VALID_MANAGER(manager));

#ifndef ISC_PLATFORM_USETHREADS
	UNUSED(i);

	if (manager->refs > 1) {
		manager->refs--;
		*managerp = NULL;
		return;
	}
#endif /* ISC_PLATFORM_USETHREADS */

	XTHREADTRACE("isc_taskmgr_destroy");
	/*
	 * Only one non-worker thread may ever call this routine.
	 * If a worker thread wants to initiate shutdown of the
	 * task manager, it should ask some non-worker thread to call
	 * isc_taskmgr_destroy(), e.g. by signalling a condition variable
	 * that the startup thread is sleeping on.
	 */

	/*
	 * Unlike elsewhere, we're going to hold this lock a long time.
	 * We need to do so, because otherwise the list of tasks could
	 * change while we were traversing it.
	 *
	 * This is also the only function where we will hold both the
	 * task manager lock and a task lock at the same time.
	 */

	LOCK(&manager->lock);

	/*
	 * Make sure we only get called once.
	 */
	INSIST(!manager->exiting);
	manager->exiting = ISC_TRUE;

	/*
	 * Post shutdown event(s) to every task (if they haven't already been
	 * posted).
	 */
	for (task = HEAD(manager->tasks);
	     task != NULL;
	     task = NEXT(task, link)) {
		LOCK(&task->lock);
		if (task_shutdown(task))
			ENQUEUE(manager->ready_tasks, task, ready_link);
		UNLOCK(&task->lock);
	}
#ifdef ISC_PLATFORM_USETHREADS
	/*
	 * Wake up any sleeping workers.  This ensures we get work done if
	 * there's work left to do, and if there are already no tasks left
	 * it will cause the workers to see manager->exiting.
	 */
	BROADCAST(&manager->work_available);
	UNLOCK(&manager->lock);

	/*
	 * Wait for all the worker threads to exit.
	 */
	for (i = 0; i < manager->workers; i++)
		(void)isc_thread_join(manager->threads[i], NULL);
#else /* ISC_PLATFORM_USETHREADS */
	/*
	 * Dispatch the shutdown events.
	 */
	UNLOCK(&manager->lock);
	while (isc__taskmgr_ready())
		(void)isc__taskmgr_dispatch();
	INSIST(ISC_LIST_EMPTY(manager->tasks));
#endif /* ISC_PLATFORM_USETHREADS */

	manager_free(manager);

	*managerp = NULL;
}

#ifndef ISC_PLATFORM_USETHREADS
isc_boolean_t
isc__taskmgr_ready(void) {
	if (taskmgr == NULL)
		return (ISC_FALSE);
	return (ISC_TF(!ISC_LIST_EMPTY(taskmgr->ready_tasks)));
}

isc_result_t
isc__taskmgr_dispatch(void) {
	isc_taskmgr_t *manager = taskmgr;

	if (taskmgr == NULL)
		return (ISC_R_NOTFOUND);

	dispatch(manager);

	return (ISC_R_SUCCESS);
}

#endif /* ISC_PLATFORM_USETHREADS */

isc_result_t
isc_task_beginexclusive(isc_task_t *task) {
#ifdef ISC_PLATFORM_USETHREADS	
	isc_taskmgr_t *manager = task->manager;
	REQUIRE(task->state == task_state_running);
	LOCK(&manager->lock);
	if (manager->exclusive_requested) {
		UNLOCK(&manager->lock);			
		return (ISC_R_LOCKBUSY);
	}
	manager->exclusive_requested = ISC_TRUE;
	while (manager->tasks_running > 1) {
		WAIT(&manager->exclusive_granted, &manager->lock);
	}
	UNLOCK(&manager->lock);	
#else
	UNUSED(task);
#endif
	return (ISC_R_SUCCESS);
}

void
isc_task_endexclusive(isc_task_t *task) {
#ifdef ISC_PLATFORM_USETHREADS	
	isc_taskmgr_t *manager = task->manager;
	REQUIRE(task->state == task_state_running);
	LOCK(&manager->lock);
	REQUIRE(manager->exclusive_requested);
	manager->exclusive_requested = ISC_FALSE;
	BROADCAST(&manager->work_available);
	UNLOCK(&manager->lock);
#else
	UNUSED(task);
#endif
}