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Unix SMB/CIFS implementation.
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trivial database library
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Copyright (C) Andrew Tridgell 1999-2005
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Copyright (C) Paul `Rusty' Russell 2000
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Copyright (C) Jeremy Allison 2000-2003
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** NOTE! The following LGPL license applies to the tdb
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** library. This does NOT imply that all of Samba is released
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 3 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, see <http://www.gnu.org/licenses/>.
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#include "tdb_private.h"
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#define TDB_MARK_LOCK 0x80000000
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void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr)
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tdb->interrupt_sig_ptr = ptr;
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/* a byte range locking function - return 0 on success
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this functions locks/unlocks 1 byte at the specified offset.
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On error, errno is also set so that errors are passed back properly
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note that a len of zero means lock to end of file
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int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
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int rw_type, int lck_type, int probe, size_t len)
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if (tdb->flags & TDB_NOLOCK) {
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if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
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tdb->ecode = TDB_ERR_RDONLY;
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fl.l_whence = SEEK_SET;
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ret = fcntl(tdb->fd,lck_type,&fl);
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/* Check for a sigalarm break. */
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if (ret == -1 && errno == EINTR &&
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tdb->interrupt_sig_ptr &&
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*tdb->interrupt_sig_ptr) {
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} while (ret == -1 && errno == EINTR);
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/* Generic lock error. errno set by fcntl.
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* EAGAIN is an expected return from non-blocking
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if (!probe && lck_type != F_SETLK) {
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/* Ensure error code is set for log fun to examine. */
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tdb->ecode = TDB_ERR_LOCK;
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TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d\n",
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tdb->fd, offset, rw_type, lck_type, (int)len));
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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upgrade a read lock to a write lock. This needs to be handled in a
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special way as some OSes (such as solaris) have too conservative
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deadlock detection and claim a deadlock when progress can be
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made. For those OSes we may loop for a while.
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int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
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if (tdb_brlock(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
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if (errno != EDEADLK) {
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/* sleep for as short a time as we can - more portable than usleep() */
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select(0, NULL, NULL, NULL, &tv);
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TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset));
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/* lock a list in the database. list -1 is the alloc list */
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static int _tdb_lock(struct tdb_context *tdb, int list, int ltype, int op)
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struct tdb_lock_type *new_lck;
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bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
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ltype &= ~TDB_MARK_LOCK;
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/* a global lock allows us to avoid per chain locks */
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if (tdb->global_lock.count &&
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(ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
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if (tdb->global_lock.count) {
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (list < -1 || list >= (int)tdb->header.hash_size) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n",
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if (tdb->flags & TDB_NOLOCK)
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for (i=0; i<tdb->num_lockrecs; i++) {
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if (tdb->lockrecs[i].list == list) {
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if (tdb->lockrecs[i].count == 0) {
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* Can't happen, see tdb_unlock(). It should
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: "
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"lck->count == 0 for list %d", list));
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* Just increment the in-memory struct, posix locks
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tdb->lockrecs[i].count++;
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new_lck = (struct tdb_lock_type *)realloc(
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sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
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if (new_lck == NULL) {
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tdb->lockrecs = new_lck;
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/* Since fcntl locks don't nest, we do a lock for the first one,
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and simply bump the count for future ones */
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tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list, ltype, op,
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tdb->lockrecs[tdb->num_lockrecs].list = list;
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tdb->lockrecs[tdb->num_lockrecs].count = 1;
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tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
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tdb->num_lockrecs += 1;
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/* lock a list in the database. list -1 is the alloc list */
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int tdb_lock(struct tdb_context *tdb, int list, int ltype)
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ret = _tdb_lock(tdb, list, ltype, F_SETLKW);
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
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"ltype=%d (%s)\n", list, ltype, strerror(errno)));
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/* lock a list in the database. list -1 is the alloc list. non-blocking lock */
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int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
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return _tdb_lock(tdb, list, ltype, F_SETLK);
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/* unlock the database: returns void because it's too late for errors. */
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/* changed to return int it may be interesting to know there
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has been an error --simo */
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int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
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struct tdb_lock_type *lck = NULL;
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bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
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ltype &= ~TDB_MARK_LOCK;
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/* a global lock allows us to avoid per chain locks */
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if (tdb->global_lock.count &&
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(ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
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if (tdb->global_lock.count) {
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (tdb->flags & TDB_NOLOCK)
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if (list < -1 || list >= (int)tdb->header.hash_size) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
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for (i=0; i<tdb->num_lockrecs; i++) {
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if (tdb->lockrecs[i].list == list) {
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lck = &tdb->lockrecs[i];
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if ((lck == NULL) || (lck->count == 0)) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
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if (lck->count > 1) {
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* This lock has count==1 left, so we need to unlock it in the
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* kernel. We don't bother with decrementing the in-memory array
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* element, we're about to overwrite it with the last array element
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ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK,
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* Shrink the array by overwriting the element just unlocked with the
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* last array element.
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if (tdb->num_lockrecs > 1) {
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*lck = tdb->lockrecs[tdb->num_lockrecs-1];
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tdb->num_lockrecs -= 1;
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* We don't bother with realloc when the array shrinks, but if we have
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* a completely idle tdb we should get rid of the locked array.
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if (tdb->num_lockrecs == 0) {
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SAFE_FREE(tdb->lockrecs);
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
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get the transaction lock
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int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
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if (tdb->have_transaction_lock || tdb->global_lock.count) {
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if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype,
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F_SETLKW, 0, 1) == -1) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n"));
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tdb->ecode = TDB_ERR_LOCK;
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tdb->have_transaction_lock = 1;
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release the transaction lock
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int tdb_transaction_unlock(struct tdb_context *tdb)
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if (!tdb->have_transaction_lock) {
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ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
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tdb->have_transaction_lock = 0;
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/* lock/unlock entire database */
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static int _tdb_lockall(struct tdb_context *tdb, int ltype, int op)
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bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
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ltype &= ~TDB_MARK_LOCK;
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/* There are no locks on read-only dbs */
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if (tdb->read_only || tdb->traverse_read)
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (tdb->global_lock.count && tdb->global_lock.ltype == ltype) {
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tdb->global_lock.count++;
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if (tdb->global_lock.count) {
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/* a global lock of a different type exists */
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (tdb->num_locks != 0) {
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/* can't combine global and chain locks */
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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tdb->methods->tdb_brlock(tdb, FREELIST_TOP, ltype, op,
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0, 4*tdb->header.hash_size)) {
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if (op == F_SETLKW) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
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tdb->global_lock.count = 1;
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tdb->global_lock.ltype = ltype;
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/* unlock entire db */
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static int _tdb_unlockall(struct tdb_context *tdb, int ltype)
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bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
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ltype &= ~TDB_MARK_LOCK;
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/* There are no locks on read-only dbs */
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if (tdb->read_only || tdb->traverse_read) {
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (tdb->global_lock.ltype != ltype || tdb->global_lock.count == 0) {
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return TDB_ERRCODE(TDB_ERR_LOCK, -1);
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if (tdb->global_lock.count > 1) {
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tdb->global_lock.count--;
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tdb->methods->tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW,
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0, 4*tdb->header.hash_size)) {
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TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
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tdb->global_lock.count = 0;
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tdb->global_lock.ltype = 0;
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/* lock entire database with write lock */
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int tdb_lockall(struct tdb_context *tdb)
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return _tdb_lockall(tdb, F_WRLCK, F_SETLKW);
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/* lock entire database with write lock - mark only */
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int tdb_lockall_mark(struct tdb_context *tdb)
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return _tdb_lockall(tdb, F_WRLCK | TDB_MARK_LOCK, F_SETLKW);
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/* unlock entire database with write lock - unmark only */
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int tdb_lockall_unmark(struct tdb_context *tdb)
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return _tdb_unlockall(tdb, F_WRLCK | TDB_MARK_LOCK);
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/* lock entire database with write lock - nonblocking varient */
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int tdb_lockall_nonblock(struct tdb_context *tdb)
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return _tdb_lockall(tdb, F_WRLCK, F_SETLK);
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/* unlock entire database with write lock */
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int tdb_unlockall(struct tdb_context *tdb)
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return _tdb_unlockall(tdb, F_WRLCK);
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/* lock entire database with read lock */
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int tdb_lockall_read(struct tdb_context *tdb)
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return _tdb_lockall(tdb, F_RDLCK, F_SETLKW);
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/* lock entire database with read lock - nonblock varient */
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int tdb_lockall_read_nonblock(struct tdb_context *tdb)
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return _tdb_lockall(tdb, F_RDLCK, F_SETLK);
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/* unlock entire database with read lock */
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int tdb_unlockall_read(struct tdb_context *tdb)
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return _tdb_unlockall(tdb, F_RDLCK);
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/* lock/unlock one hash chain. This is meant to be used to reduce
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contention - it cannot guarantee how many records will be locked */
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int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
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return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
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/* lock/unlock one hash chain, non-blocking. This is meant to be used
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to reduce contention - it cannot guarantee how many records will be
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int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
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return tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
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/* mark a chain as locked without actually locking it. Warning! use with great caution! */
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int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
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return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
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/* unmark a chain as locked without actually locking it. Warning! use with great caution! */
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int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
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return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
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int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
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return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
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int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
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return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
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int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
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return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
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/* record lock stops delete underneath */
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int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
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if (tdb->global_lock.count) {
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return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0, 1) : 0;
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Write locks override our own fcntl readlocks, so check it here.
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Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
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an error to fail to get the lock here.
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int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
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struct tdb_traverse_lock *i;
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for (i = &tdb->travlocks; i; i = i->next)
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return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1, 1);
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Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
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an error to fail to get the lock here.
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int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
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return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0, 1);
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/* fcntl locks don't stack: avoid unlocking someone else's */
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int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
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struct tdb_traverse_lock *i;
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if (tdb->global_lock.count) {
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for (i = &tdb->travlocks; i; i = i->next)
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return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0, 1) : 0);