task.c

bind 9.3结合mysql数据库

/*
 * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1998-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and 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.c,v 1.85.2.3.8.4 2004/03/08 21:06:29 marka Exp $ */

/*
 * Principal Author: Bob Halley
 */

/*
 * XXXRTH  Need to document the states a task can be in, and the rules
 * for changing states.
 */

#include <config.h>

#include <isc/condition.h>
#include <isc/event.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/msgs.h>
#include <isc/platform.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/thread.h>
#include <isc/util.h>

#ifndef ISC_PLATFORM_USETHREADS
#include "task_p.h"
#endif /* ISC_PLATFORM_USETHREADS */

#define ISC_TASK_NAMES 1

#ifdef ISC_TASK_TRACE
#define XTRACE(m)		fprintf(stderr, "task %p thread %lu: %s\n", \
				       task, isc_thread_self(), (m))
#define XTTRACE(t, m)		fprintf(stderr, "task %p thread %lu: %s\n", \
				       (t), isc_thread_self(), (m))
#define XTHREADTRACE(m)		fprintf(stderr, "thread %lu: %s\n", \
				       isc_thread_self(), (m))
#else
#define XTRACE(m)
#define XTTRACE(t, m)
#define XTHREADTRACE(m)
#endif

/***
 *** Types.
 ***/

typedef enum {
	task_state_idle, task_state_ready, task_state_running,
	task_state_done
} task_state_t;

#define TASK_MAGIC			ISC_MAGIC('T', 'A', 'S', 'K')
#define VALID_TASK(t)			ISC_MAGIC_VALID(t, TASK_MAGIC)

struct isc_task {
	/* Not locked. */
	unsigned int			magic;
	isc_taskmgr_t *			manager;
	isc_mutex_t			lock;
	/* Locked by task lock. */
	task_state_t			state;
	unsigned int			references;
	isc_eventlist_t			events;
	isc_eventlist_t			on_shutdown;
	unsigned int			quantum;
	unsigned int			flags;
	isc_stdtime_t			now;
#ifdef ISC_TASK_NAMES
	char				name[16];
	void *				tag;
#endif
	/* Locked by task manager lock. */
	LINK(isc_task_t)		link;
	LINK(isc_task_t)		ready_link;
};

#define TASK_F_SHUTTINGDOWN		0x01

#define TASK_SHUTTINGDOWN(t)		(((t)->flags & TASK_F_SHUTTINGDOWN) \
					 != 0)

#define TASK_MANAGER_MAGIC		ISC_MAGIC('T', 'S', 'K', 'M')
#define VALID_MANAGER(m)		ISC_MAGIC_VALID(m, TASK_MANAGER_MAGIC)

struct isc_taskmgr {
	/* Not locked. */
	unsigned int			magic;
	isc_mem_t *			mctx;
	isc_mutex_t			lock;
	unsigned int			workers;
#ifdef ISC_PLATFORM_USETHREADS
	isc_thread_t *			threads;
#endif /* ISC_PLATFORM_USETHREADS */
	/* Locked by task manager lock. */
	unsigned int			default_quantum;
	LIST(isc_task_t)		tasks;
	isc_tasklist_t			ready_tasks;
#ifdef ISC_PLATFORM_USETHREADS
	isc_condition_t			work_available;
	isc_condition_t			exclusive_granted;
#endif /* ISC_PLATFORM_USETHREADS */
	unsigned int			tasks_running;
	isc_boolean_t			exclusive_requested;
	isc_boolean_t			exiting;
#ifndef ISC_PLATFORM_USETHREADS
	unsigned int			refs;
#endif /* ISC_PLATFORM_USETHREADS */
};

#define DEFAULT_TASKMGR_QUANTUM		10
#define DEFAULT_DEFAULT_QUANTUM		5
#define FINISHED(m)			((m)->exiting && EMPTY((m)->tasks))

#ifndef ISC_PLATFORM_USETHREADS
static isc_taskmgr_t *taskmgr = NULL;
#endif /* ISC_PLATFORM_USETHREADS */

/***
 *** Tasks.
 ***/

static void
task_finished(isc_task_t *task) {
	isc_taskmgr_t *manager = task->manager;

	REQUIRE(EMPTY(task->events));
	REQUIRE(EMPTY(task->on_shutdown));
	REQUIRE(task->references == 0);
	REQUIRE(task->state == task_state_done);

	XTRACE("task_finished");

	LOCK(&manager->lock);
	UNLINK(manager->tasks, task, link);
#ifdef ISC_PLATFORM_USETHREADS
	if (FINISHED(manager)) {
		/*
		 * All tasks have completed and the
		 * task manager is exiting.  Wake up
		 * any idle worker threads so they
		 * can exit.
		 */
		BROADCAST(&manager->work_available);
	}
#endif /* ISC_PLATFORM_USETHREADS */
	UNLOCK(&manager->lock);

	DESTROYLOCK(&task->lock);
	task->magic = 0;
	isc_mem_put(manager->mctx, task, sizeof(*task));
}

isc_result_t
isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
		isc_task_t **taskp)
{
	isc_task_t *task;
	isc_boolean_t exiting;

	REQUIRE(VALID_MANAGER(manager));
	REQUIRE(taskp != NULL && *taskp == NULL);

	task = isc_mem_get(manager->mctx, sizeof(*task));
	if (task == NULL)
		return (ISC_R_NOMEMORY);
	XTRACE("isc_task_create");
	task->manager = manager;
	if (isc_mutex_init(&task->lock) != ISC_R_SUCCESS) {
		isc_mem_put(manager->mctx, task, sizeof(*task));
		UNEXPECTED_ERROR(__FILE__, __LINE__,
				 "isc_mutex_init() %s",
				 isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
						ISC_MSG_FAILED, "failed"));
		return (ISC_R_UNEXPECTED);
	}
	task->state = task_state_idle;
	task->references = 1;
	INIT_LIST(task->events);
	INIT_LIST(task->on_shutdown);
	task->quantum = quantum;
	task->flags = 0;
	task->now = 0;
#ifdef ISC_TASK_NAMES
	memset(task->name, 0, sizeof(task->name));
	task->tag = NULL;
#endif
	INIT_LINK(task, link);
	INIT_LINK(task, ready_link);

	exiting = ISC_FALSE;
	LOCK(&manager->lock);
	if (!manager->exiting) {
		if (task->quantum == 0)
			task->quantum = manager->default_quantum;
		APPEND(manager->tasks, task, link);
	} else
		exiting = ISC_TRUE;
	UNLOCK(&manager->lock);

	if (exiting) {
		DESTROYLOCK(&task->lock);
		isc_mem_put(manager->mctx, task, sizeof(*task));
		return (ISC_R_SHUTTINGDOWN);
	}

	task->magic = TASK_MAGIC;
	*taskp = task;

	return (ISC_R_SUCCESS);
}

void
isc_task_attach(isc_task_t *source, isc_task_t **targetp) {

	/*
	 * Attach *targetp to source.
	 */

	REQUIRE(VALID_TASK(source));
	REQUIRE(targetp != NULL && *targetp == NULL);

	XTTRACE(source, "isc_task_attach");

	LOCK(&source->lock);
	source->references++;
	UNLOCK(&source->lock);

	*targetp = source;
}

static inline isc_boolean_t
task_shutdown(isc_task_t *task) {
	isc_boolean_t was_idle = ISC_FALSE;
	isc_event_t *event, *prev;

	/*
	 * Caller must be holding the task's lock.
	 */

	XTRACE("task_shutdown");

	if (! TASK_SHUTTINGDOWN(task)) {
		XTRACE(isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
				      ISC_MSG_SHUTTINGDOWN, "shutting down"));
		task->flags |= TASK_F_SHUTTINGDOWN;
		if (task->state == task_state_idle) {
			INSIST(EMPTY(task->events));
			task->state = task_state_ready;
			was_idle = ISC_TRUE;
		}
		INSIST(task->state == task_state_ready ||
		       task->state == task_state_running);
		/*
		 * Note that we post shutdown events LIFO.
		 */
		for (event = TAIL(task->on_shutdown);
		     event != NULL;
		     event = prev) {
			prev = PREV(event, ev_link);
			DEQUEUE(task->on_shutdown, event, ev_link);
			ENQUEUE(task->events, event, ev_link);
		}
	}

	return (was_idle);
}

static inline void
task_ready(isc_task_t *task) {
	isc_taskmgr_t *manager = task->manager;

	REQUIRE(VALID_MANAGER(manager));
	REQUIRE(task->state == task_state_ready);

	XTRACE("task_ready");

	LOCK(&manager->lock);

	ENQUEUE(manager->ready_tasks, task, ready_link);
#ifdef ISC_PLATFORM_USETHREADS
	SIGNAL(&manager->work_available);
#endif /* ISC_PLATFORM_USETHREADS */

	UNLOCK(&manager->lock);
}

static inline isc_boolean_t
task_detach(isc_task_t *task) {

	/*
	 * Caller must be holding the task lock.
	 */

	REQUIRE(task->references > 0);

	XTRACE("detach");

	task->references--;
	if (task->references == 0 && task->state == task_state_idle) {
		INSIST(EMPTY(task->events));
		/*
		 * There are no references to this task, and no
		 * pending events.  We could try to optimize and
		 * either initiate shutdown or clean up the task,
		 * depending on its state, but it's easier to just
		 * make the task ready and allow run() or the event
		 * loop to deal with shutting down and termination.
		 */
		task->state = task_state_ready;
		return (ISC_TRUE);
	}

	return (ISC_FALSE);
}

void
isc_task_detach(isc_task_t **taskp) {
	isc_task_t *task;
	isc_boolean_t was_idle;

	/*
	 * Detach *taskp from its task.
	 */

	REQUIRE(taskp != NULL);
	task = *taskp;
	REQUIRE(VALID_TASK(task));

	XTRACE("isc_task_detach");

	LOCK(&task->lock);
	was_idle = task_detach(task);
	UNLOCK(&task->lock);

	if (was_idle)
		task_ready(task);

	*taskp = NULL;
}

static inline isc_boolean_t
task_send(isc_task_t *task, isc_event_t **eventp) {
	isc_boolean_t was_idle = ISC_FALSE;
	isc_event_t *event;

	/*
	 * Caller must be holding the task lock.
	 */

	REQUIRE(eventp != NULL);
	event = *eventp;
	REQUIRE(event != NULL);
	REQUIRE(event->ev_type > 0);
	REQUIRE(task->state != task_state_done);

	XTRACE("task_send");

	if (task->state == task_state_idle) {
		was_idle = ISC_TRUE;
		INSIST(EMPTY(task->events));
		task->state = task_state_ready;
	}
	INSIST(task->state == task_state_ready ||
	       task->state == task_state_running);
	ENQUEUE(task->events, event, ev_link);
	*eventp = NULL;

	return (was_idle);
}

void
isc_task_send(isc_task_t *task, isc_event_t **eventp) {
	isc_boolean_t was_idle;

	/*
	 * Send '*event' to 'task'.
	 */

	REQUIRE(VALID_TASK(task));

	XTRACE("isc_task_send");

	/*
	 * We're trying hard to hold locks for as short a time as possible.
	 * We're also trying to hold as few locks as possible.  This is why
	 * some processing is deferred until after the lock is released.
	 */
	LOCK(&task->lock);
	was_idle = task_send(task, eventp);
	UNLOCK(&task->lock);

	if (was_idle) {
		/*
		 * We need to add this task to the ready queue.
		 *
		 * We've waited until now to do it because making a task
		 * ready requires locking the manager.  If we tried to do
		 * this while holding the task lock, we could deadlock.
		 *
		 * We've changed the state to ready, so no one else will
		 * be trying to add this task to the ready queue.  The
		 * only way to leave the ready state is by executing the
		 * task.  It thus doesn't matter if events are added,
		 * removed, or a shutdown is started in the interval
		 * between the time we released the task lock, and the time
		 * we add the task to the ready queue.
		 */
		task_ready(task);
	}
}

void
isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp) {
	isc_boolean_t idle1, idle2;
	isc_task_t *task;

	/*