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Diffstat (limited to 'source3/tdb/lock.c')
| -rw-r--r-- | source3/tdb/lock.c | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/source3/tdb/lock.c b/source3/tdb/lock.c new file mode 100644 index 0000000000..a96d77a229 --- /dev/null +++ b/source3/tdb/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); +} |