#include <db.h>
int
DB_ENV->lock_vec(DB_ENV *env, u_int32_t locker, u_int32_t flags,
DB_LOCKREQ list[], int nlist, DB_LOCKREQ **elistp);
The DB_ENV->lock_vec() method atomically obtains and releases one or
more locks from the lock table. The DB_ENV->lock_vec() method is
intended to support acquisition or trading of multiple locks under one
lock table semaphore, as is needed for lock coupling or in
multigranularity locking for lock escalation.
If any of the requested locks cannot be acquired, or any of the locks
to be released cannot be released, the operations before the failing
operation are guaranteed to have completed successfully, and
DB_ENV->lock_vec() returns a non-zero value. In addition, if
elistp is not NULL, it is set to
point to the DB_LOCKREQ entry that was being processed when the error
occurred.
Unless otherwise specified, the DB_ENV->lock_vec()
method returns a non-zero error value on failure and 0 on success.
The locker parameter is an unsigned 32-bit integer quantity. It represents the entity requesting or releasing the lock.
The flags parameter must be set to 0 or the following value:
The list array provided to
DB_ENV->lock_vec() is typedef'd as DB_LOCKREQ.
To ensure compatibility with future releases of Berkeley DB, all fields of the DB_LOCKREQ structure that are not explicitly set should be initialized to 0 before the first time the structure is used. Do this by declaring the structure external or static, or by calling memset(3).
A DB_LOCKREQ structure has at least the following fields:
The operation to be performed, which must be set to one of the following values:
Get the lock defined by the values of the mode and obj
structure fields, for the specified
locker.
Upon return from DB_ENV->lock_vec(),
if the lock field is non-NULL, a
reference to the acquired lock is stored there. (This reference is
invalidated by any call to DB_ENV->lock_vec() or
DB_ENV->lock_put() that releases
the lock.)
Identical to DB_LOCK_GET except that the value in the timeout structure field overrides any previously specified timeout value for this lock. A value of 0 turns off any previously specified timeout.
The lock to which the lock structure field refers is released. The locker parameter, and mode and obj fields are ignored.
All locks held by the specified locker are released. The lock, mode,
and obj structure fields are ignored.
Locks acquired in operations performed by the current call to
DB_ENV->lock_vec() which appear before the DB_LOCK_PUT_ALL operation
are released; those acquired in operations appearing after the
DB_LOCK_PUT_ALL operation are not released.
All locks held on obj are released.
The locker parameter and the
lock and mode structure fields are ignored. Locks
acquired in operations performed by the current call to
DB_ENV->lock_vec() that appear before the DB_LOCK_PUT_OBJ operation
are released; those acquired in operations appearing after the
DB_LOCK_PUT_OBJ operation are not released.
Cause the specified locker to timeout immediately. If the database environment has not configured automatic deadlock detection, the transaction will timeout the next time deadlock detection is performed. As transactions acquire locks on behalf of a single locker ID, timing out the locker ID associated with a transaction will time out the transaction itself.
A lock reference.
The lock mode, used as an index into the environment's lock conflict matrix. When using the default lock conflict matrix, mode must be set to one of the following values:
See DB_ENV->set_lk_conflicts() and Standard Lock Modes for more information on the lock conflict matrix.
An untyped byte string that specifies the object to be locked or released. Applications using the locking subsystem directly while also doing locking via the Berkeley DB access methods must take care not to inadvertently lock objects that happen to be equal to the unique file IDs used to lock files. See Access method locking conventions in the Berkeley DB Programmer's Reference Guide for more information.
u_int32_t timeout;
The lock timeout value.
The DB_ENV->lock_vec()
method may fail and return one of the following non-zero errors:
A Berkeley DB Concurrent Data Store database environment configured for lock timeouts was unable to grant a lock in the allowed time.
You attempted to open a database handle that is configured for no waiting exclusive locking, but the exclusive lock could not be immediately obtained. See DB->set_lk_exclusive() for more information.
The DB_LOCK_NOWAIT flag or lock timers were configured and the lock could not be granted before the wait-time expired.