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

/*
 * __lock_inherit_timeout
 *		-- inherit timeout values from parent locker.
 * This is called from the transaction system.  This will
 * return EINVAL if the parent does not exist or did not
 * have a current txn timeout set.
 *
 * PUBLIC: int __lock_inherit_timeout __P(( DB_ENV *, u_int32_t, u_int32_t));
 */
int
__lock_inherit_timeout(dbenv, parent, locker)
	DB_ENV *dbenv;
	u_int32_t parent, locker;
{
	DB_LOCKER *parent_locker, *sh_locker;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	u_int32_t locker_ndx;
	int ret;

	lt = dbenv->lk_handle;
	region = lt->reginfo.primary;
	ret = 0;
	LOCKREGION(dbenv, lt);

	/* If the parent does not exist, we are done. */
	LOCKER_LOCK(lt, region, parent, locker_ndx);
	if ((ret = __lock_getlocker(lt,
	    parent, locker_ndx, 0, &parent_locker)) != 0)
		goto err;

	/*
	 * If the parent is not there yet, thats ok.  If it
	 * does not have any timouts set, then avoid creating
	 * the child locker at this point.
	 */
	if (parent_locker == NULL ||
	    (LOCK_TIME_ISVALID(&parent_locker->tx_expire) &&
	    !F_ISSET(parent_locker, DB_LOCKER_TIMEOUT))) {
		ret = EINVAL;
		goto done;
	}

	LOCKER_LOCK(lt, region, locker, locker_ndx);
	if ((ret = __lock_getlocker(lt,
	    locker, locker_ndx, 1, &sh_locker)) != 0)
		goto err;

	sh_locker->tx_expire = parent_locker->tx_expire;

	if (F_ISSET(parent_locker, DB_LOCKER_TIMEOUT)) {
		sh_locker->lk_timeout = parent_locker->lk_timeout;
		F_SET(sh_locker, DB_LOCKER_TIMEOUT);
		if (!LOCK_TIME_ISVALID(&parent_locker->tx_expire))
			ret = EINVAL;
	}

done:
err:
	UNLOCKREGION(dbenv, lt);
	return (ret);
}

/*
 * __lock_getlocker --
 *	Get a locker in the locker hash table.  The create parameter
 * indicates if the locker should be created if it doesn't exist in
 * the table.
 *
 * This must be called with the locker bucket locked.
 *
 * PUBLIC: int __lock_getlocker __P((DB_LOCKTAB *,
 * PUBLIC:     u_int32_t, u_int32_t, int, DB_LOCKER **));
 */
int
__lock_getlocker(lt, locker, indx, create, retp)
	DB_LOCKTAB *lt;
	u_int32_t locker, indx;
	int create;
	DB_LOCKER **retp;
{
	DB_ENV *dbenv;
	DB_LOCKER *sh_locker;
	DB_LOCKREGION *region;

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

	HASHLOOKUP(lt->locker_tab,
	    indx, __db_locker, links, locker, sh_locker, __lock_locker_cmp);

	/*
	 * If we found the locker, then we can just return it.  If
	 * we didn't find the locker, then we need to create it.
	 */
	if (sh_locker == NULL && create) {
		/* Create new locker and then insert it into hash table. */
		if ((sh_locker = SH_TAILQ_FIRST(
		    &region->free_lockers, __db_locker)) == NULL) {
			__db_err(dbenv, __db_lock_err, "locker entries");
			return (ENOMEM);
		}
		SH_TAILQ_REMOVE(
		    &region->free_lockers, sh_locker, links, __db_locker);
		if (++region->stat.st_nlockers > region->stat.st_maxnlockers)
			region->stat.st_maxnlockers = region->stat.st_nlockers;

		sh_locker->id = locker;
		sh_locker->dd_id = 0;
		sh_locker->master_locker = INVALID_ROFF;
		sh_locker->parent_locker = INVALID_ROFF;
		SH_LIST_INIT(&sh_locker->child_locker);
		sh_locker->flags = 0;
		SH_LIST_INIT(&sh_locker->heldby);
		sh_locker->nlocks = 0;
		sh_locker->nwrites = 0;
		sh_locker->lk_timeout = 0;
		LOCK_SET_TIME_INVALID(&sh_locker->tx_expire);
		if (locker < TXN_MINIMUM && region->tx_timeout != 0)
			__lock_expires(dbenv,
			    &sh_locker->tx_expire, region->tx_timeout);
		LOCK_SET_TIME_INVALID(&sh_locker->lk_expire);

		HASHINSERT(lt->locker_tab, indx, __db_locker, links, sh_locker);
		SH_TAILQ_INSERT_HEAD(&region->lockers,
		    sh_locker, ulinks, __db_locker);
	}

	*retp = sh_locker;
	return (0);
}

/*
 * __lock_getobj --
 *	Get an object in the object hash table.  The create parameter
 * indicates if the object should be created if it doesn't exist in
 * the table.
 *
 * This must be called with the object bucket locked.
 */
static int
__lock_getobj(lt, obj, ndx, create, retp)
	DB_LOCKTAB *lt;
	const DBT *obj;
	u_int32_t ndx;
	int create;
	DB_LOCKOBJ **retp;
{
	DB_ENV *dbenv;
	DB_LOCKOBJ *sh_obj;
	DB_LOCKREGION *region;
	int ret;
	void *p;

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

	/* Look up the object in the hash table. */
	HASHLOOKUP(lt->obj_tab,
	    ndx, __db_lockobj, links, obj, sh_obj, __lock_cmp);

	/*
	 * If we found the object, then we can just return it.  If
	 * we didn't find the object, then we need to create it.
	 */
	if (sh_obj == NULL && create) {
		/* Create new object and then insert it into hash table. */
		if ((sh_obj =
		    SH_TAILQ_FIRST(&region->free_objs, __db_lockobj)) == NULL) {
			__db_err(lt->dbenv, __db_lock_err, "object entries");
			ret = ENOMEM;
			goto err;
		}

		/*
		 * If we can fit this object in the structure, do so instead
		 * of shalloc-ing space for it.
		 */
		if (obj->size <= sizeof(sh_obj->objdata))
			p = sh_obj->objdata;
		else if ((ret = __db_shalloc(
		    lt->reginfo.addr, obj->size, 0, &p)) != 0) {
			__db_err(dbenv, "No space for lock object storage");
			goto err;
		}

		memcpy(p, obj->data, obj->size);

		SH_TAILQ_REMOVE(
		    &region->free_objs, sh_obj, links, __db_lockobj);
		if (++region->stat.st_nobjects > region->stat.st_maxnobjects)
			region->stat.st_maxnobjects = region->stat.st_nobjects;

		SH_TAILQ_INIT(&sh_obj->waiters);
		SH_TAILQ_INIT(&sh_obj->holders);
		sh_obj->lockobj.size = obj->size;
		sh_obj->lockobj.off = SH_PTR_TO_OFF(&sh_obj->lockobj, p);

		HASHINSERT(lt->obj_tab, ndx, __db_lockobj, links, sh_obj);
	}

	*retp = sh_obj;
	return (0);

err:	return (ret);
}

/*
 * __lock_is_parent --
 *	Given a locker and a transaction, return 1 if the locker is
 * an ancestor of the designcated transaction.  This is used to determine
 * if we should grant locks that appear to conflict, but don't because
 * the lock is already held by an ancestor.
 */
static int
__lock_is_parent(lt, locker, sh_locker)
	DB_LOCKTAB *lt;
	u_int32_t locker;
	DB_LOCKER *sh_locker;
{
	DB_LOCKER *parent;

	parent = sh_locker;
	while (parent->parent_locker != INVALID_ROFF) {
		parent = (DB_LOCKER *)
		    R_ADDR(&lt->reginfo, parent->parent_locker);
		if (parent->id == locker)
			return (1);
	}

	return (0);
}

/*
 * __lock_promote --
 *
 * Look through the waiters and holders lists and decide which (if any)
 * locks can be promoted.   Promote any that are eligible.
 *
 * PUBLIC: int __lock_promote __P((DB_LOCKTAB *, DB_LOCKOBJ *, u_int32_t));
 */
int
__lock_promote(lt, obj, flags)
	DB_LOCKTAB *lt;
	DB_LOCKOBJ *obj;
	u_int32_t flags;
{
	struct __db_lock *lp_w, *lp_h, *next_waiter;
	DB_LOCKER *sh_locker;
	DB_LOCKREGION *region;
	u_int32_t locker_ndx;
	int had_waiters, state_changed;

	region = lt->reginfo.primary;
	had_waiters = 0;

	/*
	 * We need to do lock promotion.  We also need to determine if we're
	 * going to need to run the deadlock detector again.  If we release
	 * locks, and there are waiters, but no one gets promoted, then we
	 * haven't fundamentally changed the lockmgr state, so we may still
	 * have a deadlock and we have to run again.  However, if there were
	 * no waiters, or we actually promoted someone, then we are OK and we
	 * don't have to run it immediately.
	 *
	 * During promotion, we look for state changes so we can return this
	 * information to the caller.
	 */

	for (lp_w = SH_TAILQ_FIRST(&obj->waiters, __db_lock),
	    state_changed = lp_w == NULL;
	    lp_w != NULL;
	    lp_w = next_waiter) {
		had_waiters = 1;
		next_waiter = SH_TAILQ_NEXT(lp_w, links, __db_lock);

		/* Waiter may have aborted or expired. */
		if (lp_w->status != DB_LSTAT_WAITING)
			continue;
		/* Are we switching locks? */
		if (LF_ISSET(DB_LOCK_NOWAITERS) && lp_w->mode == DB_LOCK_WAIT)
			continue;

		if (LF_ISSET(DB_LOCK_REMOVE)) {
			__lock_remove_waiter(lt, obj, lp_w, DB_LSTAT_NOTEXIST);
			continue;
		}
		for (lp_h = SH_TAILQ_FIRST(&obj->holders, __db_lock);
		    lp_h != NULL;
		    lp_h = SH_TAILQ_NEXT(lp_h, links, __db_lock)) {
			if (lp_h->holder != lp_w->holder &&
			    CONFLICTS(lt, region, lp_h->mode, lp_w->mode)) {
				LOCKER_LOCK(lt,
				    region, lp_w->holder, locker_ndx);
				if ((__lock_getlocker(lt, lp_w->holder,
				    locker_ndx, 0, &sh_locker)) != 0) {
					DB_ASSERT(0);
					break;
				}
				if (!__lock_is_parent(lt,
				    lp_h->holder, sh_locker))
					break;
			}
		}
		if (lp_h != NULL)	/* Found a conflict. */
			break;

		/* No conflict, promote the waiting lock. */
		SH_TAILQ_REMOVE(&obj->waiters, lp_w, links, __db_lock);
		lp_w->status = DB_LSTAT_PENDING;
		SH_TAILQ_INSERT_TAIL(&obj->holders, lp_w, links);

		/* Wake up waiter. */
		MUTEX_UNLOCK(lt->dbenv, &lp_w->mutex);
		state_changed = 1;
	}

	/*
	 * If this object had waiters and doesn't any more, then we need
	 * to remove it from the dd_obj list.
	 */
	if (had_waiters && SH_TAILQ_FIRST(&obj->waiters, __db_lock) == NULL)
		SH_TAILQ_REMOVE(&region->dd_objs, obj, dd_links, __db_lockobj);
	return (state_changed);
}

/*
 * __lock_remove_waiter --
 *	Any lock on the waitlist has a process waiting for it.  Therefore,
 * we can't return the lock to the freelist immediately.  Instead, we can
 * remove the lock from the list of waiters, set the status field of the
 * lock, and then let the process waking up return the lock to the
 * free list.
 *
 * This must be called with the Object bucket locked.
 */
static void
__lock_remove_waiter(lt, sh_obj, lockp, status)
	DB_LOCKTAB *lt;
	DB_LOCKOBJ *sh_obj;
	struct __db_lock *lockp;
	db_status_t status;
{
	DB_LOCKREGION *region;
	int do_wakeup;

	region = lt->reginfo.primary;

	do_wakeup = lockp->status == DB_LSTAT_WAITING;

	SH_TAILQ_REMOVE(&sh_obj->waiters, lockp, links, __db_lock);
	lockp->links.stqe_prev = -1;
	lockp->status = status;
	if (SH_TAILQ_FIRST(&sh_obj->waiters, __db_lock) == NULL)
		SH_TAILQ_REMOVE(
		    &region->dd_objs,
		    sh_obj, dd_links, __db_lockobj);

	/*
	 * Wake whoever is waiting on this lock.
	 *
	 * The MUTEX_UNLOCK macro normally resolves to a single argument,
	 * keep the compiler quiet.
	 */
	if (do_wakeup)
		MUTEX_UNLOCK(lt->dbenv, &lockp->mutex);
}

/*
 * __lock_expires -- set the expire time given the time to live.
 * We assume that if timevalp is set then it contains "now".
 * This avoids repeated system calls to get the time.
 */
static void
__lock_expires(dbenv, timevalp, timeout)
	DB_ENV *dbenv;
	db_timeval_t *timevalp;
	db_timeout_t timeout;
{
	if (!LOCK_TIME_ISVALID(timevalp))
		__os_clock(dbenv, &timevalp->tv_sec, &timevalp->tv_usec);
	if (timeout > 1000000) {
		timevalp->tv_sec += timeout / 1000000;
		timevalp->tv_usec += timeout % 1000000;
	} else
		timevalp->tv_usec += timeout;

	if (timevalp->tv_usec > 1000000) {
		timevalp->tv_sec++;
		timevalp->tv_usec -= 1000000;
	}
}

/*
 * __lock_expired -- determine if a lock has expired.
 *
 * PUBLIC: int __lock_expired __P((DB_ENV *, db_timeval_t *, db_timeval_t *));
 */
int
__lock_expired(dbenv, now, timevalp)
	DB_ENV *dbenv;
	db_timeval_t *now, *timevalp;
{
	if (!LOCK_TIME_ISVALID(timevalp))
		return (0);

	if (!LOCK_TIME_ISVALID(now))
		__os_clock(dbenv, &now->tv_sec, &now->tv_usec);

	return (now->tv_sec > timevalp->tv_sec ||
	    (now->tv_sec == timevalp->tv_sec &&
	    now->tv_usec >= timevalp->tv_usec));
}

/*
 * __lock_trade --
 *
 * Trade locker ids on a lock.  This is used to reassign file locks from
 * a transactional locker id to a long-lived locker id.  This should be
 * called with the region mutex held.
 */
static int
__lock_trade(dbenv, lock, new_locker)
	DB_ENV *dbenv;
	DB_LOCK *lock;
	u_int32_t new_locker;
{
	struct __db_lock *lp;
	DB_LOCKREGION *region;
	DB_LOCKTAB *lt;
	DB_LOCKER *sh_locker;
	int ret;
	u_int32_t locker_ndx;

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

	lp = (struct __db_lock *)R_ADDR(&lt->reginfo, lock->off);

	/* If the lock is already released, simply return. */
	if (lp->gen != lock->gen)
		return (DB_NOTFOUND);

	/* Make sure that we can get new locker and add this lock to it. */
	LOCKER_LOCK(lt, region, new_locker, locker_ndx);
	if ((ret =
	    __lock_getlocker(lt, new_locker, locker_ndx, 0, &sh_locker)) != 0)
		return (ret);

	if (sh_locker == NULL) {
		__db_err(dbenv, "Locker does not exist");
		return (EINVAL);
	}

	/* Remove the lock from its current locker. */
	if ((ret = __lock_checklocker(lt, lp, lp->holder, DB_LOCK_UNLINK)) != 0)
		return (ret);

	/* Add lock to its new locker. */
	SH_LIST_INSERT_HEAD(&sh_locker->heldby, lp, locker_links, __db_lock);
	sh_locker->nlocks++;
	if (IS_WRITELOCK(lp->mode))
		sh_locker->nwrites++;
	lp->holder = new_locker;

	return (0);
}