env_region.c

这是国外的resip协议栈

			lastrm = cnt;
			continue;
		}

		/* Remove the file. */
		if (__db_appname(dbenv,
		    DB_APP_NONE, names[cnt], 0, NULL, &path) == 0) {
			/*
			 * Overwrite region files.  Temporary files would have
			 * been maintained in encrypted format, so there's no
			 * reason to overwrite them.  This is not an exact
			 * check on the file being a region file, but it's
			 * not likely to be wrong, and the worst thing that can
			 * happen is we overwrite a file that didn't need to be
			 * overwritten.
			 */
			if (F_ISSET(dbenv, DB_ENV_OVERWRITE) &&
			    strlen(names[cnt]) == DB_REGION_NAME_LENGTH)
				(void)__db_overwrite(dbenv, path);
			(void)__os_unlink(dbenv, path);
			__os_free(dbenv, path);
		}
	}

	if (lastrm != -1)
		if (__db_appname(dbenv,
		    DB_APP_NONE, names[lastrm], 0, NULL, &path) == 0) {
			if (F_ISSET(dbenv, DB_ENV_OVERWRITE))
				(void)__db_overwrite(dbenv, path);
			(void)__os_unlink(dbenv, path);
			__os_free(dbenv, path);
		}
	__os_dirfree(dbenv, names, fcnt);

	return (0);
}

/*
 * __db_r_attach
 *	Join/create a region.
 *
 * PUBLIC: int __db_r_attach __P((DB_ENV *, REGINFO *, size_t));
 */
int
__db_r_attach(dbenv, infop, size)
	DB_ENV *dbenv;
	REGINFO *infop;
	size_t size;
{
	REGENV *renv;
	REGION *rp;
	int ret;
	char buf[sizeof(DB_REGION_FMT) + 20];

	renv = ((REGINFO *)dbenv->reginfo)->primary;

	/* Lock the environment. */
	MUTEX_LOCK(dbenv, &renv->mutex);

	/*
	 * Find or create a REGION structure for this region.  If we create
	 * it, the REGION_CREATE flag will be set in the infop structure.
	 */
	F_CLR(infop, REGION_CREATE);
	if ((ret = __db_des_get(dbenv, dbenv->reginfo, infop, &rp)) != 0) {
		MUTEX_UNLOCK(dbenv, &renv->mutex);
		return (ret);
	}
	infop->dbenv = dbenv;
	infop->rp = rp;
	infop->type = rp->type;
	infop->id = rp->id;

	/* If we're creating the region, set the desired size. */
	if (F_ISSET(infop, REGION_CREATE))
		rp->size = (roff_t)size;

	/* Join/create the underlying region. */
	(void)snprintf(buf, sizeof(buf), DB_REGION_FMT, infop->id);
	if ((ret = __db_appname(dbenv,
	    DB_APP_NONE, buf, 0, NULL, &infop->name)) != 0)
		goto err;
	if ((ret = __os_r_attach(dbenv, infop, rp)) != 0)
		goto err;

	/*
	 * Fault the pages into memory.  Note, do this BEFORE we initialize
	 * anything because we're writing pages in created regions, not just
	 * reading them.
	 */
	(void)__db_faultmem(dbenv,
	    infop->addr, rp->size, F_ISSET(infop, REGION_CREATE));

	/*
	 * !!!
	 * The underlying layer may have just decided that we are going
	 * to create the region.  There are various system issues that
	 * can result in a useless region that requires re-initialization.
	 *
	 * If we created the region, initialize it for allocation.
	 */
	if (F_ISSET(infop, REGION_CREATE))
		__db_shalloc_init(infop, rp->size);

	/*
	 * If the underlying REGION isn't the environment, acquire a lock
	 * for it and release our lock on the environment.
	 */
	if (infop->type != REGION_TYPE_ENV) {
		MUTEX_LOCK(dbenv, &rp->mutex);
		MUTEX_UNLOCK(dbenv, &renv->mutex);
	}

	return (0);

err:	/* Discard the underlying region. */
	if (infop->addr != NULL)
		(void)__os_r_detach(dbenv,
		    infop, F_ISSET(infop, REGION_CREATE));
	infop->rp = NULL;
	infop->id = INVALID_REGION_ID;

	/* Discard the REGION structure if we created it. */
	if (F_ISSET(infop, REGION_CREATE)) {
		(void)__db_des_destroy(dbenv, rp, 1);
		F_CLR(infop, REGION_CREATE);
	}

	/* Release the environment lock. */
	MUTEX_UNLOCK(dbenv, &renv->mutex);

	return (ret);
}

/*
 * __db_r_detach --
 *	Detach from a region.
 *
 * PUBLIC: int __db_r_detach __P((DB_ENV *, REGINFO *, int));
 */
int
__db_r_detach(dbenv, infop, destroy)
	DB_ENV *dbenv;
	REGINFO *infop;
	int destroy;
{
	REGENV *renv;
	REGION *rp;
	int ret, t_ret;

	renv = ((REGINFO *)dbenv->reginfo)->primary;
	rp = infop->rp;
	if (F_ISSET(dbenv, DB_ENV_PRIVATE))
		destroy = 1;

	/* Lock the environment. */
	MUTEX_LOCK(dbenv, &renv->mutex);

	/* Acquire the lock for the REGION. */
	MUTEX_LOCK(dbenv, &rp->mutex);

	/*
	 * We need to call destroy on per-subsystem info before we free the
	 * memory associated with the region.
	 */
	if (destroy)
		__db_region_destroy(dbenv, infop);

	/* Detach from the underlying OS region. */
	ret = __os_r_detach(dbenv, infop, destroy);

	/* Release the REGION lock. */
	MUTEX_UNLOCK(dbenv, &rp->mutex);

	/*
	 * If we destroyed the region, discard the REGION structure.  The only
	 * time this routine is called with the destroy flag set is when the
	 * environment is being removed, and it's likely that the only reason
	 * the environment is being removed is because we crashed.  Don't do
	 * any unnecessary shared memory manipulation.
	 */
	if (destroy &&
	    ((t_ret = __db_des_destroy(
		dbenv, rp, F_ISSET(dbenv, DB_ENV_PRIVATE))) != 0) && ret == 0)
		ret = t_ret;

	/* Release the environment lock. */
	MUTEX_UNLOCK(dbenv, &renv->mutex);

	/* Destroy the structure. */
	if (infop->name != NULL)
		__os_free(dbenv, infop->name);

	return (ret);
}

/*
 * __db_des_get --
 *	Return a reference to the shared information for a REGION,
 *	optionally creating a new entry.
 */
static int
__db_des_get(dbenv, env_infop, infop, rpp)
	DB_ENV *dbenv;
	REGINFO *env_infop, *infop;
	REGION **rpp;
{
	REGENV *renv;
	REGION *rp, *first_type;
	u_int32_t maxid;
	int ret;

	/*
	 * !!!
	 * Called with the environment already locked.
	 */
	*rpp = NULL;
	renv = env_infop->primary;

	/*
	 * If the caller wants to join a region, walk through the existing
	 * regions looking for a matching ID (if ID specified) or matching
	 * type (if type specified).  If we return based on a matching type
	 * return the "primary" region, that is, the first region that was
	 * created of this type.
	 *
	 * Track the maximum region ID so we can allocate a new region,
	 * note that we have to start at 1 because the primary environment
	 * uses ID == 1.
	 */
	maxid = REGION_ID_ENV;
	for (first_type = NULL,
	    rp = SH_LIST_FIRST(&renv->regionq, __db_region);
	    rp != NULL; rp = SH_LIST_NEXT(rp, q, __db_region)) {
		if (infop->id != INVALID_REGION_ID) {
			if (infop->id == rp->id)
				break;
			continue;
		}
		if (infop->type == rp->type &&
		    F_ISSET(infop, REGION_JOIN_OK) &&
		    (first_type == NULL || first_type->id > rp->id))
			first_type = rp;

		if (rp->id > maxid)
			maxid = rp->id;
	}
	if (rp == NULL)
		rp = first_type;

	/*
	 * If we didn't find a region and we can't create the region, fail.
	 * The caller generates any error message.
	 */
	if (rp == NULL && !F_ISSET(infop, REGION_CREATE_OK))
		return (ENOENT);

	/*
	 * If we didn't find a region, create and initialize a REGION structure
	 * for the caller.  If id was set, use that value, otherwise we use the
	 * next available ID.
	 */
	if (rp == NULL) {
		if ((ret = __db_shalloc(env_infop,
		    sizeof(REGION), MUTEX_ALIGN, &rp)) != 0) {
			__db_err(dbenv,
			    "unable to create new master region entry: %s",
			    db_strerror(ret));
			return (ret);
		}

		/* Initialize the region. */
		memset(rp, 0, sizeof(*rp));
		if ((ret = __db_mutex_setup(dbenv, env_infop, &rp->mutex,
		    MUTEX_NO_RECORD | MUTEX_NO_RLOCK)) != 0) {
			__db_shalloc_free(env_infop, rp);
			return (ret);
		}
		rp->segid = INVALID_REGION_SEGID;

		/*
		 * Set the type and ID; if no region ID was specified,
		 * allocate one.
		 */
		rp->type = infop->type;
		rp->id = infop->id == INVALID_REGION_ID ? maxid + 1 : infop->id;

		SH_LIST_INSERT_HEAD(&renv->regionq, rp, q, __db_region);
		F_SET(infop, REGION_CREATE);
	}

	*rpp = rp;
	return (0);
}

/*
 * __db_des_destroy --
 *	Destroy a reference to a REGION.
 */
static int
__db_des_destroy(dbenv, rp, shmem_safe)
	DB_ENV *dbenv;
	REGION *rp;
	int shmem_safe;
{
	REGINFO *infop;

	/*
	 * !!!
	 * Called with the environment already locked.
	 */
	infop = dbenv->reginfo;

	/*
	 * If we're calling during recovery, it may not be safe to access the
	 * shared memory, as the shared memory may have been corrupted during
	 * the crash.  If the shared memory is safe, remove the REGION entry
	 * from its linked list, destroy the mutex, and free the allocated
	 * memory.  On systems that require system mutex support, we don't
	 * have a choice -- safe or not, we have to destroy the mutex or we'll
	 * leak memory.
	 */
#ifdef HAVE_MUTEX_SYSTEM_RESOURCES
	(void)__db_mutex_destroy(&rp->mutex);
#else
	if (shmem_safe)
		(void)__db_mutex_destroy(&rp->mutex);
#endif
	if (shmem_safe) {
		SH_LIST_REMOVE(rp, q, __db_region);
		__db_shalloc_free(infop, rp);
	}

	return (0);
}

/*
 * __db_faultmem --
 *	Fault the region into memory.
 */
static int
__db_faultmem(dbenv, addr, size, created)
	DB_ENV *dbenv;
	void *addr;
	size_t size;
	int created;
{
	int ret;
	u_int8_t *p, *t;

	/* Ignore heap regions. */
	if (F_ISSET(dbenv, DB_ENV_PRIVATE))
		return (0);

	/*
	 * It's sometimes significantly faster to page-fault in all of the
	 * region's pages before we run the application, as we see nasty
	 * side-effects when we page-fault while holding various locks, i.e.,
	 * the lock takes a long time to acquire because of the underlying
	 * page fault, and the other threads convoy behind the lock holder.
	 *
	 * If we created the region, we write a non-zero value so that the
	 * system can't cheat.  If we're just joining the region, we can
	 * only read the value and try to confuse the compiler sufficiently
	 * that it doesn't figure out that we're never really using it.
	 */
	ret = 0;
	if (F_ISSET(dbenv, DB_ENV_REGION_INIT)) {
		if (created)
			for (p = addr, t = (u_int8_t *)addr + size;
			    p < t; p += OS_VMPAGESIZE)
				p[0] = 0xdb;
		else
			for (p = addr, t = (u_int8_t *)addr + size;
			    p < t; p += OS_VMPAGESIZE)
				ret |= p[0];
	}

	return (ret);
}

/*
 * __db_region_destroy --
 *	Destroy per-subsystem region information.
 *	Called with the region already locked.
 */
static void
__db_region_destroy(dbenv, infop)
	DB_ENV *dbenv;
	REGINFO *infop;
{
	switch (infop->type) {
	case REGION_TYPE_LOCK:
		__lock_region_destroy(dbenv, infop);
		break;
	case REGION_TYPE_LOG:
		__log_region_destroy(dbenv, infop);
		break;
	case REGION_TYPE_MPOOL:
		__memp_region_destroy(dbenv, infop);
		break;
	case REGION_TYPE_TXN:
		__txn_region_destroy(dbenv, infop);
		break;
	case REGION_TYPE_ENV:
	case REGION_TYPE_MUTEX:
		break;
	case INVALID_REGION_TYPE:
	default:
		DB_ASSERT(0);
		break;
	}
}