lock.c

这是linux下运行的mysql软件包,可用于linux 下安装 php + mysql + apach 的网络配置

	LOCKREGION(dbenv, lt);
	ret = __lock_put_nolock(dbenv, lock, &run_dd, 0);
	UNLOCKREGION(dbenv, lt);

	/*
	 * Only run the lock detector if put told us to AND we are running
	 * in auto-detect mode.  If we are not running in auto-detect, then
	 * a call to lock_detect here will 0 the need_dd bit, but will not
	 * actually abort anything.
	 */
	if (ret == 0 && run_dd)
		(void)dbenv->lock_detect(dbenv, 0,
		    ((DB_LOCKREGION *)lt->reginfo.primary)->detect, NULL);
	return (ret);
}

static int
__lock_put_nolock(dbenv, lock, runp, flags)
	DB_ENV *dbenv;
	DB_LOCK *lock;
	int *runp;
	u_int32_t flags;
{
	struct __db_lock *lockp;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	int ret;

	/* Check if locks have been globally turned off. */
	if (F_ISSET(dbenv, DB_ENV_NOLOCKING))
		return (0);

	lt = dbenv->lk_handle;
	region = lt->reginfo.primary;

	lockp = (struct __db_lock *)R_ADDR(&lt->reginfo, lock->off);
	LOCK_INIT(*lock);
	if (lock->gen != lockp->gen) {
		__db_err(dbenv, __db_lock_invalid, "DB_LOCK->lock_put");
		return (EINVAL);
	}

	ret = __lock_put_internal(lt,
	    lockp, lock->ndx, flags | DB_LOCK_UNLINK | DB_LOCK_FREE);

	*runp = 0;
	if (ret == 0 && region->need_dd && region->detect != DB_LOCK_NORUN)
		*runp = 1;

	return (ret);
}

/*
 * __lock_downgrade --
 *	Used to downgrade locks.  Currently this is used in two places,
 * 1) by the concurrent access product to downgrade write locks
 * back to iwrite locks and 2) to downgrade write-handle locks to read-handle
 * locks at the end of an open/create.
 *
 * PUBLIC: int __lock_downgrade __P((DB_ENV *,
 * PUBLIC:     DB_LOCK *, db_lockmode_t, u_int32_t));
 */
int
__lock_downgrade(dbenv, lock, new_mode, flags)
	DB_ENV *dbenv;
	DB_LOCK *lock;
	db_lockmode_t new_mode;
	u_int32_t flags;
{
	struct __db_lock *lockp;
	DB_LOCKER *sh_locker;
	DB_LOCKOBJ *obj;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	u_int32_t indx;
	int ret;

	COMPQUIET(flags, 0);

	PANIC_CHECK(dbenv);
	ret = 0;

	/* Check if locks have been globally turned off. */
	if (F_ISSET(dbenv, DB_ENV_NOLOCKING))
		return (0);

	lt = dbenv->lk_handle;
	region = lt->reginfo.primary;

	LOCKREGION(dbenv, lt);

	lockp = (struct __db_lock *)R_ADDR(&lt->reginfo, lock->off);
	if (lock->gen != lockp->gen) {
		__db_err(dbenv, __db_lock_invalid, "lock_downgrade");
		ret = EINVAL;
		goto out;
	}

	LOCKER_LOCK(lt, region, lockp->holder, indx);

	if ((ret = __lock_getlocker(lt, lockp->holder,
	    indx, 0, &sh_locker)) != 0 || sh_locker == NULL) {
		if (ret == 0)
			ret = EINVAL;
		__db_err(dbenv, __db_locker_invalid);
		goto out;
	}
	if (IS_WRITELOCK(lockp->mode) && !IS_WRITELOCK(new_mode))
		sh_locker->nwrites--;

	if (new_mode == DB_LOCK_WWRITE)
		F_SET(sh_locker, DB_LOCKER_DIRTY);

	lockp->mode = new_mode;

	/* Get the object associated with this lock. */
	obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj);
	(void)__lock_promote(lt, obj, LF_ISSET(DB_LOCK_NOWAITERS));

out:	UNLOCKREGION(dbenv, lt);

	return (ret);
}

static int
__lock_put_internal(lt, lockp, obj_ndx, flags)
	DB_LOCKTAB *lt;
	struct __db_lock *lockp;
	u_int32_t obj_ndx, flags;
{
	DB_LOCKOBJ *sh_obj;
	DB_LOCKREGION *region;
	int ret, state_changed;

	region = lt->reginfo.primary;
	ret = state_changed = 0;

	if (!OBJ_LINKS_VALID(lockp)) {
		/*
		 * Someone removed this lock while we were doing a release
		 * by locker id.  We are trying to free this lock, but it's
		 * already been done; all we need to do is return it to the
		 * free list.
		 */
		lockp->status = DB_LSTAT_FREE;
		SH_TAILQ_INSERT_HEAD(
		    &region->free_locks, lockp, links, __db_lock);
		region->stat.st_nlocks--;
		return (0);
	}

	if (LF_ISSET(DB_LOCK_DOALL))
		region->stat.st_nreleases += lockp->refcount;
	else
		region->stat.st_nreleases++;

	if (!LF_ISSET(DB_LOCK_DOALL) && lockp->refcount > 1) {
		lockp->refcount--;
		return (0);
	}

	/* Increment generation number. */
	lockp->gen++;

	/* Get the object associated with this lock. */
	sh_obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj);

	/* Remove this lock from its holders/waitlist. */
	if (lockp->status != DB_LSTAT_HELD && lockp->status != DB_LSTAT_PENDING)
		__lock_remove_waiter(lt, sh_obj, lockp, DB_LSTAT_FREE);
	else {
		SH_TAILQ_REMOVE(&sh_obj->holders, lockp, links, __db_lock);
		lockp->links.stqe_prev = -1;
	}

	if (LF_ISSET(DB_LOCK_NOPROMOTE))
		state_changed = 0;
	else
		state_changed = __lock_promote(lt,
		    sh_obj, LF_ISSET(DB_LOCK_REMOVE | DB_LOCK_NOWAITERS));

	if (LF_ISSET(DB_LOCK_UNLINK))
		ret = __lock_checklocker(lt, lockp, lockp->holder, flags);

	/* Check if object should be reclaimed. */
	if (SH_TAILQ_FIRST(&sh_obj->holders, __db_lock) == NULL &&
	    SH_TAILQ_FIRST(&sh_obj->waiters, __db_lock) == NULL) {
		HASHREMOVE_EL(lt->obj_tab,
		    obj_ndx, __db_lockobj, links, sh_obj);
		if (sh_obj->lockobj.size > sizeof(sh_obj->objdata))
			__db_shalloc_free(lt->reginfo.addr,
			    SH_DBT_PTR(&sh_obj->lockobj));
		SH_TAILQ_INSERT_HEAD(
		    &region->free_objs, sh_obj, links, __db_lockobj);
		region->stat.st_nobjects--;
		state_changed = 1;
	}

	/* Free lock. */
	if (!LF_ISSET(DB_LOCK_UNLINK) && LF_ISSET(DB_LOCK_FREE)) {
		lockp->status = DB_LSTAT_FREE;
		SH_TAILQ_INSERT_HEAD(
		    &region->free_locks, lockp, links, __db_lock);
		region->stat.st_nlocks--;
	}

	/*
	 * If we did not promote anyone; we need to run the deadlock
	 * detector again.
	 */
	if (state_changed == 0)
		region->need_dd = 1;

	return (ret);
}

/*
 * Utility functions; listed alphabetically.
 */

/*
 * __lock_checklocker --
 *	If a locker has no more locks, then we can free the object.
 * Return a boolean indicating whether we freed the object or not.
 *
 * Must be called without the locker's lock set.
 */
static int
__lock_checklocker(lt, lockp, locker, flags)
	DB_LOCKTAB *lt;
	struct __db_lock *lockp;
	u_int32_t locker, flags;
{
	DB_ENV *dbenv;
	DB_LOCKER *sh_locker;
	DB_LOCKREGION *region;
	u_int32_t indx;
	int ret;

	dbenv = lt->dbenv;
	region = lt->reginfo.primary;
	ret = 0;

	LOCKER_LOCK(lt, region, locker, indx);

	/* If the locker's list is NULL, free up the locker. */
	if ((ret = __lock_getlocker(lt,
	    locker, indx, 0, &sh_locker)) != 0 || sh_locker == NULL) {
		if (ret == 0)
			ret = EINVAL;
		__db_err(dbenv, __db_locker_invalid);
		goto freelock;
	}

	if (F_ISSET(sh_locker, DB_LOCKER_DELETED)) {
		LF_CLR(DB_LOCK_FREE);
		if (!LF_ISSET(DB_LOCK_IGNOREDEL))
			goto freelock;
	}

	if (LF_ISSET(DB_LOCK_UNLINK)) {
		SH_LIST_REMOVE(lockp, locker_links, __db_lock);
		if (lockp->status == DB_LSTAT_HELD) {
			sh_locker->nlocks--;
			if (IS_WRITELOCK(lockp->mode))
				sh_locker->nwrites--;
		}
	}

	if (SH_LIST_FIRST(&sh_locker->heldby, __db_lock) == NULL &&
	    LF_ISSET(DB_LOCK_FREE_LOCKER))
		__lock_freelocker( lt, region, sh_locker, indx);

freelock:
	if (LF_ISSET(DB_LOCK_FREE)) {
		lockp->status = DB_LSTAT_FREE;
		SH_TAILQ_INSERT_HEAD(
		    &region->free_locks, lockp, links, __db_lock);
		region->stat.st_nlocks--;
	}

	return (ret);
}

/*
 * __lock_addfamilylocker
 *	Put a locker entry in for a child transaction.
 *
 * PUBLIC: int __lock_addfamilylocker __P((DB_ENV *, u_int32_t, u_int32_t));
 */
int
__lock_addfamilylocker(dbenv, pid, id)
	DB_ENV *dbenv;
	u_int32_t pid, id;
{
	DB_LOCKER *lockerp, *mlockerp;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	u_int32_t ndx;
	int ret;

	lt = dbenv->lk_handle;
	region = lt->reginfo.primary;
	LOCKREGION(dbenv, lt);

	/* get/create the  parent locker info */
	LOCKER_LOCK(lt, region, pid, ndx);
	if ((ret = __lock_getlocker(dbenv->lk_handle,
	    pid, ndx, 1, &mlockerp)) != 0)
		goto err;

	/*
	 * We assume that only one thread can manipulate
	 * a single transaction family.
	 * Therefore the master locker cannot go away while
	 * we manipulate it, nor can another child in the
	 * family be created at the same time.
	 */
	LOCKER_LOCK(lt, region, id, ndx);
	if ((ret = __lock_getlocker(dbenv->lk_handle,
	    id, ndx, 1, &lockerp)) != 0)
		goto err;

	/* Point to our parent. */
	lockerp->parent_locker = R_OFFSET(&lt->reginfo, mlockerp);

	/* See if this locker is the family master. */
	if (mlockerp->master_locker == INVALID_ROFF)
		lockerp->master_locker = R_OFFSET(&lt->reginfo, mlockerp);
	else {
		lockerp->master_locker = mlockerp->master_locker;
		mlockerp = R_ADDR(&lt->reginfo, mlockerp->master_locker);
	}

	/*
	 * Link the child at the head of the master's list.
	 * The guess is when looking for deadlock that
	 * the most recent child is the one thats blocked.
	 */
	SH_LIST_INSERT_HEAD(
	    &mlockerp->child_locker, lockerp, child_link, __db_locker);

err:
	UNLOCKREGION(dbenv, lt);

	return (ret);
}

/*
 * __lock_freefamilylocker
 *	Remove a locker from the hash table and its family.
 *
 * This must be called without the locker bucket locked.
 *
 * PUBLIC: int __lock_freefamilylocker  __P((DB_LOCKTAB *, u_int32_t));
 */
int
__lock_freefamilylocker(lt, locker)
	DB_LOCKTAB *lt;
	u_int32_t locker;
{
	DB_ENV *dbenv;
	DB_LOCKER *sh_locker;
	DB_LOCKREGION *region;
	u_int32_t indx;
	int ret;

	dbenv = lt->dbenv;
	region = lt->reginfo.primary;

	LOCKREGION(dbenv, lt);
	LOCKER_LOCK(lt, region, locker, indx);

	if ((ret = __lock_getlocker(lt,
	    locker, indx, 0, &sh_locker)) != 0 || sh_locker == NULL)
		goto freelock;

	if (SH_LIST_FIRST(&sh_locker->heldby, __db_lock) != NULL) {
		ret = EINVAL;
		__db_err(dbenv, "Freeing locker with locks");
		goto freelock;
	}

	/* If this is part of a family, we must fix up its links. */
	if (sh_locker->master_locker != INVALID_ROFF)
		SH_LIST_REMOVE(sh_locker, child_link, __db_locker);

	__lock_freelocker(lt, region, sh_locker, indx);

freelock:
	UNLOCKREGION(dbenv, lt);
	return (ret);
}

/*
 * __lock_freelocker
 *	common code for deleting a locker.
 *
 * This must be called with the locker bucket locked.
 */
static void
__lock_freelocker(lt, region, sh_locker, indx)
	DB_LOCKTAB *lt;
	DB_LOCKREGION *region;
	DB_LOCKER *sh_locker;
	u_int32_t indx;

{
	HASHREMOVE_EL(
	    lt->locker_tab, indx, __db_locker, links, sh_locker);
	SH_TAILQ_INSERT_HEAD(
	    &region->free_lockers, sh_locker, links, __db_locker);
	SH_TAILQ_REMOVE(&region->lockers, sh_locker, ulinks, __db_locker);
	region->stat.st_nlockers--;
}

/*
 * __lock_set_timeout
 *		-- set timeout values in shared memory.
 * This is called from the transaction system.
 * We either set the time that this tranaction expires or the
 * amount of time that a lock for this transaction is permitted
 * to wait.
 *
 * PUBLIC: int __lock_set_timeout __P(( DB_ENV *,
 * PUBLIC:      u_int32_t, db_timeout_t, u_int32_t));
 */
int
__lock_set_timeout(dbenv, locker, timeout, op)
	DB_ENV *dbenv;
	u_int32_t locker;
	db_timeout_t timeout;
	u_int32_t op;
{
	DB_LOCKER *sh_locker;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	u_int32_t locker_ndx;
	int ret;

	lt = dbenv->lk_handle;
	region = lt->reginfo.primary;
	LOCKREGION(dbenv, lt);

	LOCKER_LOCK(lt, region, locker, locker_ndx);
	ret = __lock_getlocker(lt, locker, locker_ndx, 1, &sh_locker);
	UNLOCKREGION(dbenv, lt);
	if (ret != 0)
		return (ret);

	if (op == DB_SET_TXN_TIMEOUT) {
		if (timeout == 0)
			LOCK_SET_TIME_INVALID(&sh_locker->tx_expire);
		else
			__lock_expires(dbenv, &sh_locker->tx_expire, timeout);
	} else if (op == DB_SET_LOCK_TIMEOUT) {
		sh_locker->lk_timeout = timeout;
		F_SET(sh_locker, DB_LOCKER_TIMEOUT);
	} else if (op == DB_SET_TXN_NOW) {
		LOCK_SET_TIME_INVALID(&sh_locker->tx_expire);
		__lock_expires(dbenv, &sh_locker->tx_expire, 0);
		sh_locker->lk_expire = sh_locker->tx_expire;
	} else
		return (EINVAL);

	return (0);
}