diff options
Diffstat (limited to 'source4/lib/tdb/common/transaction.c')
| -rw-r--r-- | source4/lib/tdb/common/transaction.c | 29 |
1 files changed, 20 insertions, 9 deletions
diff --git a/source4/lib/tdb/common/transaction.c b/source4/lib/tdb/common/transaction.c index b9d44a7283..75e91c56cc 100644 --- a/source4/lib/tdb/common/transaction.c +++ b/source4/lib/tdb/common/transaction.c @@ -372,6 +372,15 @@ int tdb_transaction_start(struct tdb_context *tdb) return -1; } + if (tdb->travlocks.next != NULL) { + /* you cannot use transactions inside a traverse (although you can use + traverse inside a transaction) as otherwise you can end up with + deadlock */ + TDB_LOG((tdb, 0, "tdb_transaction_start: cannot start a transaction within a traverse\n")); + tdb->ecode = TDB_ERR_LOCK; + return -1; + } + tdb->transaction = calloc(sizeof(struct tdb_transaction), 1); if (tdb->transaction == NULL) { tdb->ecode = TDB_ERR_OOM; @@ -388,15 +397,9 @@ int tdb_transaction_start(struct tdb_context *tdb) return -1; } - /* get a write lock from the freelist to the end of file. It - would be much better to make this a read lock as it would - increase parallelism, but it could lead to deadlocks on - commit when a write lock needs to be taken. - - TODO: look at alternative locking strategies to allow this - to be a read lock - */ - if (tdb_brlock_len(tdb, FREELIST_TOP, F_WRLCK, F_SETLKW, 0, 0) == -1) { + /* get a read lock from the freelist to the end of file. This + is upgraded to a write lock during the commit */ + if (tdb_brlock_len(tdb, FREELIST_TOP, F_RDLCK, F_SETLKW, 0, 0) == -1) { TDB_LOG((tdb, 0, "tdb_transaction_start: failed to get hash locks\n")); tdb->ecode = TDB_ERR_LOCK; goto fail; @@ -763,6 +766,14 @@ int tdb_transaction_commit(struct tdb_context *tdb) return -1; } + /* upgrade the main transaction lock region to a write lock */ + if (tdb_brlock_len(tdb, FREELIST_TOP, F_WRLCK, F_SETLKW, 0, 0) == -1) { + TDB_LOG((tdb, 0, "tdb_transaction_start: failed to upgrade hash locks\n")); + tdb->ecode = TDB_ERR_LOCK; + tdb_transaction_cancel(tdb); + return -1; + } + /* get the global lock - this prevents new users attaching to the database during the commit */ if (tdb_brlock_len(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) { |