env_region.c

这是国外的resip协议栈

	 * and acquire, and we have to know if it fails.  (It CAN fail, e.g.,
	 * SunOS, when using fcntl(2) for locking and using an in-memory
	 * filesystem as the database home.  But you knew that, I'm sure -- it
	 * probably wasn't even worth mentioning.)
	 */
	if ((ret = __db_mutex_setup(dbenv, infop, &renv->mutex,
	    MUTEX_NO_RECORD | MUTEX_NO_RLOCK)) != 0) {
		__db_err(dbenv, "%s: unable to initialize environment lock: %s",
		    infop->name, db_strerror(ret));
		goto err;
	}

	if (!F_ISSET(&renv->mutex, MUTEX_IGNORE) &&
	    (ret = __db_mutex_lock(dbenv, &renv->mutex)) != 0) {
		__db_err(dbenv, "%s: unable to acquire environment lock: %s",
		    infop->name, db_strerror(ret));
		goto err;
	}

	/*
	 * Get the underlying REGION structure for this environment.  Note,
	 * we created the underlying OS region before we acquired the REGION
	 * structure, which is backwards from the normal procedure.  Update
	 * the REGION structure.
	 */
	if ((ret = __db_des_get(dbenv, infop, infop, &rp)) != 0) {
find_err:	__db_err(dbenv,
		    "%s: unable to find environment", infop->name);
		if (ret == 0)
			ret = EINVAL;
		goto err;
	}
	infop->rp = rp;
	rp->size = tregion.size;
	rp->segid = tregion.segid;

	/*
	 * !!!
	 * If we create an environment where regions are public and in system
	 * memory, we have to inform processes joining the environment how to
	 * attach to the shared memory segment.  So, we write the shared memory
	 * identifier into the file, to be read by those other processes.
	 *
	 * XXX
	 * This is really OS-layer information, but I can't see any easy way
	 * to move it down there without passing down information that it has
	 * no right to know, e.g., that this is the one-and-only REGENV region
	 * and not some other random region.
	 */
	if (tregion.segid != INVALID_REGION_SEGID) {
		ref.size = tregion.size;
		ref.segid = tregion.segid;
		if ((ret = __os_write(
		    dbenv, dbenv->lockfhp, &ref, sizeof(ref), &nrw)) != 0) {
			__db_err(dbenv,
			    "%s: unable to write out public environment ID: %s",
			    infop->name, db_strerror(ret));
			goto err;
		}
	}

	/*
	 * If not doing thread locking, we need to save the file handle for
	 * fcntl(2) locking.  Otherwise, discard the handle, we no longer
	 * need it, and the less contact between the buffer cache and the VM,
	 * the better.
	 */
#if defined(HAVE_MUTEX_THREADS)
	if (dbenv->lockfhp != NULL) {
		 (void)__os_closehandle(dbenv, dbenv->lockfhp);
		 dbenv->lockfhp = NULL;
	}
#endif

	/* Validate the file. */
	renv->magic = DB_REGION_MAGIC;

	/* Discard our lock. */
	MUTEX_UNLOCK(dbenv, &renv->mutex);

	/* Everything looks good, we're done. */
	dbenv->reginfo = infop;
	return (0);

err:
retry:	/* Close any open file handle. */
	if (dbenv->lockfhp != NULL) {
		(void)__os_closehandle(dbenv, dbenv->lockfhp);
		dbenv->lockfhp = NULL;
	}

	/*
	 * If we joined or created the region, detach from it.  If we created
	 * it, destroy it.  Note, there's a path in the above code where we're
	 * using a temporary REGION structure because we haven't yet allocated
	 * the real one.  In that case the region address (addr) will be filled
	 * in, but the REGION pointer (rp) won't.  Fix it.
	 */
	if (infop->addr != NULL) {
		if (infop->rp == NULL)
			infop->rp = &tregion;

		/* Reset the addr value that we "corrected" above. */
		infop->addr = infop->primary;
		(void)__os_r_detach(dbenv,
		    infop, F_ISSET(infop, REGION_CREATE));
	}

	/* Free the allocated name and/or REGINFO structure. */
	if (infop->name != NULL)
		__os_free(dbenv, infop->name);
	__os_free(dbenv, infop);

	/* If we had a temporary error, wait awhile and try again. */
	if (ret == 0) {
		if (++retry_cnt > 3) {
			__db_err(dbenv, "unable to join the environment");
			ret = EAGAIN;
		} else {
			__os_sleep(dbenv, retry_cnt * 3, 0);
			goto loop;
		}
	}

	return (ret);
}

/*
 * __db_e_detach --
 *	Detach from the environment.
 *
 * PUBLIC: int __db_e_detach __P((DB_ENV *, int));
 */
int
__db_e_detach(dbenv, destroy)
	DB_ENV *dbenv;
	int destroy;
{
	REGENV *renv;
	REGINFO *infop;

	infop = dbenv->reginfo;
	renv = infop->primary;

	if (F_ISSET(dbenv, DB_ENV_PRIVATE))
		destroy = 1;

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

	/* Decrement the reference count. */
	if (renv->refcnt == 0) {
		__db_err(dbenv,
		    "region %lu (environment): reference count went negative",
		    (u_long)infop->rp->id);
	} else
		--renv->refcnt;

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

	/* Close the locking file handle. */
	if (dbenv->lockfhp != NULL) {
		(void)__os_closehandle(dbenv, dbenv->lockfhp);
		dbenv->lockfhp = NULL;
	}

	/*
	 * If we are destroying the environment, destroy any system resources
	 * the crypto and replication systems may have acquired and put in the
	 * main region.
	 */
	if (destroy) {
#ifdef HAVE_CRYPTO
		(void)__crypto_region_destroy(dbenv);
#endif
		(void)__rep_region_destroy(dbenv);
	}

	/*
	 * Release the region, and kill our reference.
	 *
	 * If we are destroying the environment, destroy any system resources
	 * backing the mutex.
	 */
	if (destroy) {
		(void)__db_mutex_destroy(&renv->mutex);
		(void)__db_mutex_destroy(&infop->rp->mutex);

		/*
		 * Only free the REGION structure itself if it was separately
		 * allocated from the heap.
		 */
		if (F_ISSET(dbenv, DB_ENV_PRIVATE))
			__db_shalloc_free(infop, infop->rp);
	}

	/* Reset the addr value that we "corrected" above. */
	infop->addr = infop->primary;

	(void)__os_r_detach(dbenv, infop, destroy);
	if (infop->name != NULL)
		__os_free(dbenv, infop->name);

	/*
	 * We set the DB_ENV->reginfo field to NULL here and discard its memory.
	 * DB_ENV->remove calls __dbenv_remove to do the region remove, and
	 * __dbenv_remove attached and then detaches from the region.  We don't
	 * want to return to DB_ENV->remove with a non-NULL DB_ENV->reginfo
	 * field because it will attempt to detach again as part of its cleanup.
	 */
	__os_free(dbenv, dbenv->reginfo);
	dbenv->reginfo = NULL;

	return (0);
}

/*
 * __db_e_remove --
 *	Discard an environment if it's not in use.
 *
 * PUBLIC: int __db_e_remove __P((DB_ENV *, u_int32_t));
 */
int
__db_e_remove(dbenv, flags)
	DB_ENV *dbenv;
	u_int32_t flags;
{
	REGENV *renv;
	REGINFO *infop, reginfo;
	REGION *rp;
	u_int32_t db_env_reset;
	int force, ret;

	force = LF_ISSET(DB_FORCE) ? 1 : 0;
	/*
	 * This routine has to walk a nasty line between not looking into
	 * the environment (which may be corrupted after an app or system
	 * crash), and removing everything that needs removing.  What we
	 * do is:
	 *	1. Connect to the environment (so it better be OK).
	 *	2. If the environment is in use (reference count is non-zero),
	 *	   return EBUSY.
	 *	3. Overwrite the magic number so that any threads of control
	 *	   attempting to connect will backoff and retry.
	 *	4. Walk the list of regions.  Connect to each region and then
	 *	   disconnect with the destroy flag set.  This shouldn't cause
	 *	   any problems, even if the region is corrupted, because we
	 *	   should never be looking inside the region.
	 *	5. Walk the list of files in the directory, unlinking any
	 *	   files that match a region name.  Unlink the environment
	 *	   file last.
	 *
	 * If the force flag is set, we do not acquire any locks during this
	 * process.
	 */
	db_env_reset = F_ISSET(dbenv, DB_ENV_NOLOCKING | DB_ENV_NOPANIC);
	if (force)
		F_SET(dbenv, DB_ENV_NOLOCKING);
	F_SET(dbenv, DB_ENV_NOPANIC);

	/* Join the environment. */
	if ((ret = __db_e_attach(dbenv, NULL)) != 0) {
		/*
		 * If we can't join it, we assume that's because it doesn't
		 * exist.  It would be better to know why we failed, but it
		 * probably isn't important.
		 */
		ret = 0;
		if (force)
			goto remfiles;
		goto done;
	}

	infop = dbenv->reginfo;
	renv = infop->primary;

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

	/*
	 * If it's in use, we're done unless we're forcing the issue or the
	 * environment has panic'd.  (Presumably, if the environment panic'd,
	 * the thread holding the reference count may not have cleaned up.)
	 */
	if (renv->refcnt == 1 || renv->envpanic == 1 || force) {
		/*
		 * Set the panic flag and overwrite the magic number.
		 *
		 * !!!
		 * From this point on, there's no going back, we pretty
		 * much ignore errors, and just whack on whatever we can.
		 */
		renv->envpanic = 1;
		renv->magic = 0;

		/*
		 * Unlock the environment.  We should no longer need the lock
		 * because we've poisoned the pool, but we can't continue to
		 * hold it either, because other routines may want it.
		 */
		MUTEX_UNLOCK(dbenv, &renv->mutex);

		/*
		 * Attach to each sub-region and destroy it.
		 *
		 * !!!
		 * The REGION_CREATE_OK flag is set for Windows/95 -- regions
		 * are zero'd out when the last reference to the region goes
		 * away, in which case the underlying OS region code requires
		 * callers be prepared to create the region in order to join it.
		 */
		memset(&reginfo, 0, sizeof(reginfo));
		for (rp = SH_LIST_FIRST(&renv->regionq, __db_region);
		    rp != NULL; rp = SH_LIST_NEXT(rp, q, __db_region)) {
			if (rp->type == REGION_TYPE_ENV)
				continue;

			/*
			 * If we get here and can't attach and/or detach to the
			 * region, it's a mess.  Ignore errors, there's nothing
			 * we can do about them.
			 */
			reginfo.id = rp->id;
			reginfo.flags = REGION_CREATE_OK;
			if (__db_r_attach(dbenv, &reginfo, 0) == 0) {
				R_UNLOCK(dbenv, &reginfo);
				(void)__db_r_detach(dbenv, &reginfo, 1);
			}
		}

		/* Destroy the environment's region. */
		(void)__db_e_detach(dbenv, 1);

		/* Discard any remaining physical files. */
remfiles:	(void)__db_e_remfile(dbenv);
	} else {
		/* Unlock the environment. */
		MUTEX_UNLOCK(dbenv, &renv->mutex);

		/* Discard the environment. */
		(void)__db_e_detach(dbenv, 0);

		ret = EBUSY;
	}

done:	F_CLR(dbenv, DB_ENV_NOLOCKING | DB_ENV_NOPANIC);
	F_SET(dbenv, db_env_reset);

	return (ret);
}

/*
 * __db_e_remfile --
 *	Discard any region files in the filesystem.
 */
static int
__db_e_remfile(dbenv)
	DB_ENV *dbenv;
{
	int cnt, fcnt, lastrm, ret;
	const char *dir;
	char saved_char, *p, **names, *path, buf[sizeof(DB_REGION_FMT) + 20];

	/* Get the full path of a file in the environment. */
	(void)snprintf(buf, sizeof(buf), "%s", DB_REGION_ENV);
	if ((ret = __db_appname(dbenv, DB_APP_NONE, buf, 0, NULL, &path)) != 0)
		return (ret);

	/* Get the parent directory for the environment. */
	if ((p = __db_rpath(path)) == NULL) {
		p = path;
		saved_char = *p;

		dir = PATH_DOT;
	} else {
		saved_char = *p;
		*p = '\0';

		dir = path;
	}

	/* Get the list of file names. */
	if ((ret = __os_dirlist(dbenv, dir, &names, &fcnt)) != 0)
		__db_err(dbenv, "%s: %s", dir, db_strerror(ret));

	/* Restore the path, and free it. */
	*p = saved_char;
	__os_free(dbenv, path);

	if (ret != 0)
		return (ret);

	/*
	 * Remove files from the region directory.
	 */
	for (lastrm = -1, cnt = fcnt; --cnt >= 0;) {
		/* Skip anything outside our name space. */
		if (strncmp(names[cnt],
		    DB_REGION_PREFIX, sizeof(DB_REGION_PREFIX) - 1))
			continue;

		/* Skip queue extent files. */
		if (strncmp(names[cnt], "__dbq.", 6) == 0)
			continue;

		/* Skip replication files. */
		if (strncmp(names[cnt], "__db.rep.", 9) == 0)
			continue;

		/*
		 * Remove the primary environment region last, because it's
		 * the key to this whole mess.
		 */
		if (strcmp(names[cnt], DB_REGION_ENV) == 0) {