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Re: HAVE_BERKELEY_DB_THREAD (ITS#1176)
At 10:10 AM 5/27/01, email@example.com wrote:
>We've been approached by an organization that's seeing corruption in
>its databases and I'm trying to understand how OpenLdap uses Berkeley
The LDBM backend uses Berkeley DB as a simple key/value store.
There is a new backend under development (back-bdb) which will
use transactions and other advanced features of Berkeley DB 3.
>Basically, I'm concerned about the define HAVE_BERKELEY_DB_THREAD.
>(The only OpenLdap code I've reviewed is ldbm.c.)
>It seems to me that if HAVE_BERKELEY_DB_THREAD is defined, multiple
>OpenLdap threads can access Berkeley DB databases concurrently, and,
>there is no provision to restrict this access to read-only threads.
>This concerns me; usually, if multiple threads of control are in the
>database code, and, one of those threads is updating the database,
>there can be deadlocks which require transactional support to resolve.
The backend implements a higher level locking system which orders
access in a manner which should avoid deadlock.
>Can someone please tell me:
>+ If HAVE_BERKELEY_DB_THREAD is defined, can multiple OpenLdap threads
> of control access the Berkeley DB API concurrently?
>+ If so, can one of those multiple threads be modifying the database?
> Can two of those multiple threads be modifying the database?