diff options
Diffstat (limited to 'tdb/common/lock.c')
| -rw-r--r-- | tdb/common/lock.c | 553 |
1 files changed, 553 insertions, 0 deletions
diff --git a/tdb/common/lock.c b/tdb/common/lock.c new file mode 100644 index 000000000..f156c0fa7 --- /dev/null +++ b/tdb/common/lock.c @@ -0,0 +1,553 @@ + /* + 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 3 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, see <http://www.gnu.org/licenses/>. +*/ + +#include "tdb_private.h" + +#define TDB_MARK_LOCK 0x80000000 + +void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr) +{ + tdb->interrupt_sig_ptr = ptr; +} + +/* 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(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); + + /* Check for a sigalarm break. */ + if (ret == -1 && errno == EINTR && + tdb->interrupt_sig_ptr && + *tdb->interrupt_sig_ptr) { + break; + } + } 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, TDB_DEBUG_TRACE,"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(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, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset)); + return -1; +} + + +/* lock a list in the database. list -1 is the alloc list */ +static int _tdb_lock(struct tdb_context *tdb, int list, int ltype, int op) +{ + struct tdb_lock_type *new_lck; + int i; + bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK); + + ltype &= ~TDB_MARK_LOCK; + + /* a global lock allows us to avoid per chain locks */ + if (tdb->global_lock.count && + (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) { + return 0; + } + + if (tdb->global_lock.count) { + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (list < -1 || list >= (int)tdb->header.hash_size) { + TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n", + list, ltype)); + return -1; + } + if (tdb->flags & TDB_NOLOCK) + return 0; + + for (i=0; i<tdb->num_lockrecs; i++) { + if (tdb->lockrecs[i].list == list) { + if (tdb->lockrecs[i].count == 0) { + /* + * Can't happen, see tdb_unlock(). It should + * be an assert. + */ + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: " + "lck->count == 0 for list %d", list)); + } + /* + * Just increment the in-memory struct, posix locks + * don't stack. + */ + tdb->lockrecs[i].count++; + return 0; + } + } + + new_lck = (struct tdb_lock_type *)realloc( + tdb->lockrecs, + sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1)); + if (new_lck == NULL) { + errno = ENOMEM; + return -1; + } + tdb->lockrecs = new_lck; + + /* Since fcntl locks don't nest, we do a lock for the first one, + and simply bump the count for future ones */ + if (!mark_lock && + tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list, ltype, op, + 0, 1)) { + return -1; + } + + tdb->num_locks++; + + tdb->lockrecs[tdb->num_lockrecs].list = list; + tdb->lockrecs[tdb->num_lockrecs].count = 1; + tdb->lockrecs[tdb->num_lockrecs].ltype = ltype; + tdb->num_lockrecs += 1; + + return 0; +} + +/* lock a list in the database. list -1 is the alloc list */ +int tdb_lock(struct tdb_context *tdb, int list, int ltype) +{ + int ret; + ret = _tdb_lock(tdb, list, ltype, F_SETLKW); + if (ret) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d " + "ltype=%d (%s)\n", list, ltype, strerror(errno))); + } + return ret; +} + +/* lock a list in the database. list -1 is the alloc list. non-blocking lock */ +int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype) +{ + return _tdb_lock(tdb, list, ltype, F_SETLK); +} + + +/* 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; + int i; + struct tdb_lock_type *lck = NULL; + bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK); + + ltype &= ~TDB_MARK_LOCK; + + /* a global lock allows us to avoid per chain locks */ + if (tdb->global_lock.count && + (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) { + return 0; + } + + if (tdb->global_lock.count) { + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (tdb->flags & TDB_NOLOCK) + return 0; + + /* Sanity checks */ + if (list < -1 || list >= (int)tdb->header.hash_size) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size)); + return ret; + } + + for (i=0; i<tdb->num_lockrecs; i++) { + if (tdb->lockrecs[i].list == list) { + lck = &tdb->lockrecs[i]; + break; + } + } + + if ((lck == NULL) || (lck->count == 0)) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n")); + return -1; + } + + if (lck->count > 1) { + lck->count--; + return 0; + } + + /* + * This lock has count==1 left, so we need to unlock it in the + * kernel. We don't bother with decrementing the in-memory array + * element, we're about to overwrite it with the last array element + * anyway. + */ + + if (mark_lock) { + ret = 0; + } else { + ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK, + F_SETLKW, 0, 1); + } + tdb->num_locks--; + + /* + * Shrink the array by overwriting the element just unlocked with the + * last array element. + */ + + if (tdb->num_lockrecs > 1) { + *lck = tdb->lockrecs[tdb->num_lockrecs-1]; + } + tdb->num_lockrecs -= 1; + + /* + * We don't bother with realloc when the array shrinks, but if we have + * a completely idle tdb we should get rid of the locked array. + */ + + if (tdb->num_lockrecs == 0) { + SAFE_FREE(tdb->lockrecs); + } + + if (ret) + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n")); + return ret; +} + +/* + get the transaction lock + */ +int tdb_transaction_lock(struct tdb_context *tdb, int ltype) +{ + if (tdb->have_transaction_lock || tdb->global_lock.count) { + return 0; + } + if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype, + F_SETLKW, 0, 1) == -1) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n")); + tdb->ecode = TDB_ERR_LOCK; + return -1; + } + tdb->have_transaction_lock = 1; + return 0; +} + +/* + release the transaction lock + */ +int tdb_transaction_unlock(struct tdb_context *tdb) +{ + int ret; + if (!tdb->have_transaction_lock) { + return 0; + } + ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1); + if (ret == 0) { + tdb->have_transaction_lock = 0; + } + return ret; +} + + + + +/* lock/unlock entire database */ +static int _tdb_lockall(struct tdb_context *tdb, int ltype, int op) +{ + bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK); + + ltype &= ~TDB_MARK_LOCK; + + /* There are no locks on read-only dbs */ + if (tdb->read_only || tdb->traverse_read) + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + + if (tdb->global_lock.count && tdb->global_lock.ltype == ltype) { + tdb->global_lock.count++; + return 0; + } + + if (tdb->global_lock.count) { + /* a global lock of a different type exists */ + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (tdb->num_locks != 0) { + /* can't combine global and chain locks */ + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (!mark_lock && + tdb->methods->tdb_brlock(tdb, FREELIST_TOP, ltype, op, + 0, 4*tdb->header.hash_size)) { + if (op == F_SETLKW) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno))); + } + return -1; + } + + tdb->global_lock.count = 1; + tdb->global_lock.ltype = ltype; + + return 0; +} + + + +/* unlock entire db */ +static int _tdb_unlockall(struct tdb_context *tdb, int ltype) +{ + bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK); + + ltype &= ~TDB_MARK_LOCK; + + /* There are no locks on read-only dbs */ + if (tdb->read_only || tdb->traverse_read) { + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (tdb->global_lock.ltype != ltype || tdb->global_lock.count == 0) { + return TDB_ERRCODE(TDB_ERR_LOCK, -1); + } + + if (tdb->global_lock.count > 1) { + tdb->global_lock.count--; + return 0; + } + + if (!mark_lock && + tdb->methods->tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, + 0, 4*tdb->header.hash_size)) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno))); + return -1; + } + + tdb->global_lock.count = 0; + tdb->global_lock.ltype = 0; + + return 0; +} + +/* lock entire database with write lock */ +int tdb_lockall(struct tdb_context *tdb) +{ + return _tdb_lockall(tdb, F_WRLCK, F_SETLKW); +} + +/* lock entire database with write lock - mark only */ +int tdb_lockall_mark(struct tdb_context *tdb) +{ + return _tdb_lockall(tdb, F_WRLCK | TDB_MARK_LOCK, F_SETLKW); +} + +/* unlock entire database with write lock - unmark only */ +int tdb_lockall_unmark(struct tdb_context *tdb) +{ + return _tdb_unlockall(tdb, F_WRLCK | TDB_MARK_LOCK); +} + +/* lock entire database with write lock - nonblocking varient */ +int tdb_lockall_nonblock(struct tdb_context *tdb) +{ + return _tdb_lockall(tdb, F_WRLCK, F_SETLK); +} + +/* unlock entire database with write lock */ +int tdb_unlockall(struct tdb_context *tdb) +{ + return _tdb_unlockall(tdb, F_WRLCK); +} + +/* lock entire database with read lock */ +int tdb_lockall_read(struct tdb_context *tdb) +{ + return _tdb_lockall(tdb, F_RDLCK, F_SETLKW); +} + +/* lock entire database with read lock - nonblock varient */ +int tdb_lockall_read_nonblock(struct tdb_context *tdb) +{ + return _tdb_lockall(tdb, F_RDLCK, F_SETLK); +} + +/* unlock entire database with read lock */ +int tdb_unlockall_read(struct tdb_context *tdb) +{ + return _tdb_unlockall(tdb, F_RDLCK); +} + +/* 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); +} + +/* lock/unlock one hash chain, non-blocking. This is meant to be used + to reduce contention - it cannot guarantee how many records will be + locked */ +int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key) +{ + return tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); +} + +/* mark a chain as locked without actually locking it. Warning! use with great caution! */ +int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key) +{ + return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK); +} + +/* unmark a chain as locked without actually locking it. Warning! use with great caution! */ +int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key) +{ + return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK); +} + +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) +{ + if (tdb->global_lock.count) { + return 0; + } + return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0, 1) : 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, 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, 1); +} + +/* 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; + uint32_t count = 0; + + if (tdb->global_lock.count) { + return 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, 1) : 0); +} |