summaryrefslogtreecommitdiff
path: root/source3/tdb/common/lock.c
diff options
context:
space:
mode:
Diffstat (limited to 'source3/tdb/common/lock.c')
-rw-r--r--source3/tdb/common/lock.c276
1 files changed, 276 insertions, 0 deletions
diff --git a/source3/tdb/common/lock.c b/source3/tdb/common/lock.c
new file mode 100644
index 0000000000..a96d77a229
--- /dev/null
+++ b/source3/tdb/common/lock.c
@@ -0,0 +1,276 @@
+ /*
+ Unix SMB/CIFS implementation.
+
+ trivial database library
+
+ Copyright (C) Andrew Tridgell 1999-2005
+ Copyright (C) Paul `Rusty' Russell 2000
+ Copyright (C) Jeremy Allison 2000-2003
+
+ ** NOTE! The following LGPL license applies to the tdb
+ ** library. This does NOT imply that all of Samba is released
+ ** under the LGPL
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include "tdb_private.h"
+
+/* a byte range locking function - return 0 on success
+ this functions locks/unlocks 1 byte at the specified offset.
+
+ On error, errno is also set so that errors are passed back properly
+ through tdb_open().
+
+ note that a len of zero means lock to end of file
+*/
+int tdb_brlock_len(struct tdb_context *tdb, tdb_off_t offset,
+ int rw_type, int lck_type, int probe, size_t len)
+{
+ struct flock fl;
+ int ret;
+
+ if (tdb->flags & TDB_NOLOCK) {
+ return 0;
+ }
+
+ if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
+ tdb->ecode = TDB_ERR_RDONLY;
+ return -1;
+ }
+
+ fl.l_type = rw_type;
+ fl.l_whence = SEEK_SET;
+ fl.l_start = offset;
+ fl.l_len = len;
+ fl.l_pid = 0;
+
+ do {
+ ret = fcntl(tdb->fd,lck_type,&fl);
+ } while (ret == -1 && errno == EINTR);
+
+ if (ret == -1) {
+ /* Generic lock error. errno set by fcntl.
+ * EAGAIN is an expected return from non-blocking
+ * locks. */
+ if (!probe && lck_type != F_SETLK) {
+ /* Ensure error code is set for log fun to examine. */
+ tdb->ecode = TDB_ERR_LOCK;
+ TDB_LOG((tdb, 5,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d\n",
+ tdb->fd, offset, rw_type, lck_type, (int)len));
+ }
+ return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+ }
+ return 0;
+}
+
+
+/*
+ upgrade a read lock to a write lock. This needs to be handled in a
+ special way as some OSes (such as solaris) have too conservative
+ deadlock detection and claim a deadlock when progress can be
+ made. For those OSes we may loop for a while.
+*/
+int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
+{
+ int count = 1000;
+ while (count--) {
+ struct timeval tv;
+ if (tdb_brlock_len(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
+ return 0;
+ }
+ if (errno != EDEADLK) {
+ break;
+ }
+ /* sleep for as short a time as we can - more portable than usleep() */
+ tv.tv_sec = 0;
+ tv.tv_usec = 1;
+ select(0, NULL, NULL, NULL, &tv);
+ }
+ TDB_LOG((tdb, 5,"tdb_brlock_upgrade failed at offset %d\n", offset));
+ return -1;
+}
+
+
+/* a byte range locking function - return 0 on success
+ this functions locks/unlocks 1 byte at the specified offset.
+
+ On error, errno is also set so that errors are passed back properly
+ through tdb_open(). */
+int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
+ int rw_type, int lck_type, int probe)
+{
+ return tdb_brlock_len(tdb, offset, rw_type, lck_type, probe, 1);
+}
+
+/* lock a list in the database. list -1 is the alloc list */
+int tdb_lock(struct tdb_context *tdb, int list, int ltype)
+{
+ if (list < -1 || list >= (int)tdb->header.hash_size) {
+ TDB_LOG((tdb, 0,"tdb_lock: invalid list %d for ltype=%d\n",
+ list, ltype));
+ return -1;
+ }
+ if (tdb->flags & TDB_NOLOCK)
+ return 0;
+
+ /* Since fcntl locks don't nest, we do a lock for the first one,
+ and simply bump the count for future ones */
+ if (tdb->locked[list+1].count == 0) {
+ if (tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list,ltype,F_SETLKW, 0)) {
+ TDB_LOG((tdb, 0,"tdb_lock failed on list %d ltype=%d (%s)\n",
+ list, ltype, strerror(errno)));
+ return -1;
+ }
+ tdb->locked[list+1].ltype = ltype;
+ tdb->num_locks++;
+ }
+ tdb->locked[list+1].count++;
+ return 0;
+}
+
+/* unlock the database: returns void because it's too late for errors. */
+ /* changed to return int it may be interesting to know there
+ has been an error --simo */
+int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
+{
+ int ret = -1;
+
+ if (tdb->flags & TDB_NOLOCK)
+ return 0;
+
+ /* Sanity checks */
+ if (list < -1 || list >= (int)tdb->header.hash_size) {
+ TDB_LOG((tdb, 0, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
+ return ret;
+ }
+
+ if (tdb->locked[list+1].count==0) {
+ TDB_LOG((tdb, 0, "tdb_unlock: count is 0\n"));
+ return ret;
+ }
+
+ if (tdb->locked[list+1].count == 1) {
+ /* Down to last nested lock: unlock underneath */
+ ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK, F_SETLKW, 0);
+ tdb->num_locks--;
+ } else {
+ ret = 0;
+ }
+ tdb->locked[list+1].count--;
+
+ if (ret)
+ TDB_LOG((tdb, 0,"tdb_unlock: An error occurred unlocking!\n"));
+ return ret;
+}
+
+
+
+/* lock/unlock entire database */
+int tdb_lockall(struct tdb_context *tdb)
+{
+ u32 i;
+
+ /* There are no locks on read-only dbs */
+ if (tdb->read_only || tdb->traverse_read)
+ return TDB_ERRCODE(TDB_ERR_LOCK, -1);
+ for (i = 0; i < tdb->header.hash_size; i++)
+ if (tdb_lock(tdb, i, F_WRLCK))
+ break;
+
+ /* If error, release locks we have... */
+ if (i < tdb->header.hash_size) {
+ u32 j;
+
+ for ( j = 0; j < i; j++)
+ tdb_unlock(tdb, j, F_WRLCK);
+ return TDB_ERRCODE(TDB_ERR_NOLOCK, -1);
+ }
+
+ return 0;
+}
+void tdb_unlockall(struct tdb_context *tdb)
+{
+ u32 i;
+ for (i=0; i < tdb->header.hash_size; i++)
+ tdb_unlock(tdb, i, F_WRLCK);
+}
+
+/* lock/unlock one hash chain. This is meant to be used to reduce
+ contention - it cannot guarantee how many records will be locked */
+int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
+{
+ return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
+}
+
+int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
+{
+ return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
+}
+
+int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
+{
+ return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
+}
+
+int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
+{
+ return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
+}
+
+
+
+/* record lock stops delete underneath */
+int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+ return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0) : 0;
+}
+
+/*
+ Write locks override our own fcntl readlocks, so check it here.
+ Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
+ an error to fail to get the lock here.
+*/
+int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+ struct tdb_traverse_lock *i;
+ for (i = &tdb->travlocks; i; i = i->next)
+ if (i->off == off)
+ return -1;
+ return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1);
+}
+
+/*
+ Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
+ an error to fail to get the lock here.
+*/
+int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+ return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0);
+}
+
+/* fcntl locks don't stack: avoid unlocking someone else's */
+int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
+{
+ struct tdb_traverse_lock *i;
+ u32 count = 0;
+
+ if (off == 0)
+ return 0;
+ for (i = &tdb->travlocks; i; i = i->next)
+ if (i->off == off)
+ count++;
+ return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0) : 0);
+}