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Diffstat (limited to 'bundled/tdb/common/lock.c')
-rw-r--r-- | bundled/tdb/common/lock.c | 863 |
1 files changed, 0 insertions, 863 deletions
diff --git a/bundled/tdb/common/lock.c b/bundled/tdb/common/lock.c deleted file mode 100644 index 803feeec..00000000 --- a/bundled/tdb/common/lock.c +++ /dev/null @@ -1,863 +0,0 @@ - /* - 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" - -void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr) -{ - tdb->interrupt_sig_ptr = ptr; -} - -static int fcntl_lock(struct tdb_context *tdb, - int rw, off_t off, off_t len, bool waitflag) -{ - struct flock fl; - - fl.l_type = rw; - fl.l_whence = SEEK_SET; - fl.l_start = off; - fl.l_len = len; - fl.l_pid = 0; - - if (waitflag) - return fcntl(tdb->fd, F_SETLKW, &fl); - else - return fcntl(tdb->fd, F_SETLK, &fl); -} - -static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len) -{ - struct flock fl; -#if 0 /* Check they matched up locks and unlocks correctly. */ - char line[80]; - FILE *locks; - bool found = false; - - locks = fopen("/proc/locks", "r"); - - while (fgets(line, 80, locks)) { - char *p; - int type, start, l; - - /* eg. 1: FLOCK ADVISORY WRITE 2440 08:01:2180826 0 EOF */ - p = strchr(line, ':') + 1; - if (strncmp(p, " POSIX ADVISORY ", strlen(" POSIX ADVISORY "))) - continue; - p += strlen(" FLOCK ADVISORY "); - if (strncmp(p, "READ ", strlen("READ ")) == 0) - type = F_RDLCK; - else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0) - type = F_WRLCK; - else - abort(); - p += 6; - if (atoi(p) != getpid()) - continue; - p = strchr(strchr(p, ' ') + 1, ' ') + 1; - start = atoi(p); - p = strchr(p, ' ') + 1; - if (strncmp(p, "EOF", 3) == 0) - l = 0; - else - l = atoi(p) - start + 1; - - if (off == start) { - if (len != l) { - fprintf(stderr, "Len %u should be %u: %s", - (int)len, l, line); - abort(); - } - if (type != rw) { - fprintf(stderr, "Type %s wrong: %s", - rw == F_RDLCK ? "READ" : "WRITE", line); - abort(); - } - found = true; - break; - } - } - - if (!found) { - fprintf(stderr, "Unlock on %u@%u not found!\n", - (int)off, (int)len); - abort(); - } - - fclose(locks); -#endif - - fl.l_type = F_UNLCK; - fl.l_whence = SEEK_SET; - fl.l_start = off; - fl.l_len = len; - fl.l_pid = 0; - - return fcntl(tdb->fd, F_SETLKW, &fl); -} - -/* list -1 is the alloc list, otherwise a hash chain. */ -static tdb_off_t lock_offset(int list) -{ - return FREELIST_TOP + 4*list; -} - -/* 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, - int rw_type, tdb_off_t offset, size_t len, - enum tdb_lock_flags flags) -{ - int ret; - - if (tdb->flags & TDB_NOLOCK) { - return 0; - } - - if (flags & TDB_LOCK_MARK_ONLY) { - return 0; - } - - if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) { - tdb->ecode = TDB_ERR_RDONLY; - return -1; - } - - do { - ret = fcntl_lock(tdb, rw_type, offset, len, - flags & TDB_LOCK_WAIT); - /* 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) { - tdb->ecode = TDB_ERR_LOCK; - /* Generic lock error. errno set by fcntl. - * EAGAIN is an expected return from non-blocking - * locks. */ - if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) { - TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d flags=%d len=%d\n", - tdb->fd, offset, rw_type, flags, (int)len)); - } - return -1; - } - return 0; -} - -int tdb_brunlock(struct tdb_context *tdb, - int rw_type, tdb_off_t offset, size_t len) -{ - int ret; - - if (tdb->flags & TDB_NOLOCK) { - return 0; - } - - do { - ret = fcntl_unlock(tdb, rw_type, offset, len); - } while (ret == -1 && errno == EINTR); - - if (ret == -1) { - TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brunlock failed (fd=%d) at offset %d rw_type=%d len=%d\n", - tdb->fd, offset, rw_type, (int)len)); - } - return ret; -} - -/* - 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_allrecord_upgrade(struct tdb_context *tdb) -{ - int count = 1000; - - if (tdb->allrecord_lock.count != 1) { - TDB_LOG((tdb, TDB_DEBUG_ERROR, - "tdb_allrecord_upgrade failed: count %u too high\n", - tdb->allrecord_lock.count)); - return -1; - } - - if (tdb->allrecord_lock.off != 1) { - TDB_LOG((tdb, TDB_DEBUG_ERROR, - "tdb_allrecord_upgrade failed: already upgraded?\n")); - return -1; - } - - while (count--) { - struct timeval tv; - if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, - TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) { - tdb->allrecord_lock.ltype = F_WRLCK; - tdb->allrecord_lock.off = 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_allrecord_upgrade failed\n")); - return -1; -} - -static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb, - tdb_off_t offset) -{ - unsigned int i; - - for (i=0; i<tdb->num_lockrecs; i++) { - if (tdb->lockrecs[i].off == offset) { - return &tdb->lockrecs[i]; - } - } - return NULL; -} - -/* lock an offset in the database. */ -int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype, - enum tdb_lock_flags flags) -{ - struct tdb_lock_type *new_lck; - - if (offset >= lock_offset(tdb->header.hash_size)) { - tdb->ecode = TDB_ERR_LOCK; - TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n", - offset, ltype)); - return -1; - } - if (tdb->flags & TDB_NOLOCK) - return 0; - - new_lck = find_nestlock(tdb, offset); - if (new_lck) { - /* - * Just increment the in-memory struct, posix locks - * don't stack. - */ - new_lck->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 (tdb_brlock(tdb, ltype, offset, 1, flags)) { - return -1; - } - - tdb->lockrecs[tdb->num_lockrecs].off = offset; - tdb->lockrecs[tdb->num_lockrecs].count = 1; - tdb->lockrecs[tdb->num_lockrecs].ltype = ltype; - tdb->num_lockrecs++; - - return 0; -} - -static int tdb_lock_and_recover(struct tdb_context *tdb) -{ - int ret; - - /* We need to match locking order in transaction commit. */ - if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) { - return -1; - } - - if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) { - tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0); - return -1; - } - - ret = tdb_transaction_recover(tdb); - - tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1); - tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0); - - return ret; -} - -static bool have_data_locks(const struct tdb_context *tdb) -{ - unsigned int i; - - for (i = 0; i < tdb->num_lockrecs; i++) { - if (tdb->lockrecs[i].off >= lock_offset(-1)) - return true; - } - return false; -} - -static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype, - enum tdb_lock_flags waitflag) -{ - int ret; - bool check = false; - - /* a allrecord lock allows us to avoid per chain locks */ - if (tdb->allrecord_lock.count && - (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) { - return 0; - } - - if (tdb->allrecord_lock.count) { - tdb->ecode = TDB_ERR_LOCK; - ret = -1; - } else { - /* Only check when we grab first data lock. */ - check = !have_data_locks(tdb); - ret = tdb_nest_lock(tdb, lock_offset(list), ltype, waitflag); - - if (ret == 0 && check && tdb_needs_recovery(tdb)) { - tdb_nest_unlock(tdb, lock_offset(list), ltype, false); - - if (tdb_lock_and_recover(tdb) == -1) { - return -1; - } - return tdb_lock_list(tdb, list, ltype, waitflag); - } - } - return ret; -} - -/* 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_list(tdb, list, ltype, TDB_LOCK_WAIT); - 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_list(tdb, list, ltype, TDB_LOCK_NOWAIT); -} - - -int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype, - bool mark_lock) -{ - int ret = -1; - struct tdb_lock_type *lck; - - if (tdb->flags & TDB_NOLOCK) - return 0; - - /* Sanity checks */ - if (offset >= lock_offset(tdb->header.hash_size)) { - TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->header.hash_size)); - return ret; - } - - lck = find_nestlock(tdb, offset); - 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_brunlock(tdb, ltype, offset, 1); - } - - /* - * Shrink the array by overwriting the element just unlocked with the - * last array element. - */ - *lck = tdb->lockrecs[--tdb->num_lockrecs]; - - /* - * 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; -} - -int tdb_unlock(struct tdb_context *tdb, int list, int ltype) -{ - /* a global lock allows us to avoid per chain locks */ - if (tdb->allrecord_lock.count && - (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) { - return 0; - } - - if (tdb->allrecord_lock.count) { - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - return tdb_nest_unlock(tdb, lock_offset(list), ltype, false); -} - -/* - get the transaction lock - */ -int tdb_transaction_lock(struct tdb_context *tdb, int ltype, - enum tdb_lock_flags lockflags) -{ - return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags); -} - -/* - release the transaction lock - */ -int tdb_transaction_unlock(struct tdb_context *tdb, int ltype) -{ - return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false); -} - -/* Returns 0 if all done, -1 if error, 1 if ok. */ -static int tdb_allrecord_check(struct tdb_context *tdb, int ltype, - enum tdb_lock_flags flags, bool upgradable) -{ - /* There are no locks on read-only dbs */ - if (tdb->read_only || tdb->traverse_read) { - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) { - tdb->allrecord_lock.count++; - return 0; - } - - if (tdb->allrecord_lock.count) { - /* a global lock of a different type exists */ - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - if (tdb_have_extra_locks(tdb)) { - /* can't combine global and chain locks */ - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - if (upgradable && ltype != F_RDLCK) { - /* tdb error: you can't upgrade a write lock! */ - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - return 1; -} - -/* We only need to lock individual bytes, but Linux merges consecutive locks - * so we lock in contiguous ranges. */ -static int tdb_chainlock_gradual(struct tdb_context *tdb, - int ltype, enum tdb_lock_flags flags, - size_t off, size_t len) -{ - int ret; - enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT); - - if (len <= 4) { - /* Single record. Just do blocking lock. */ - return tdb_brlock(tdb, ltype, off, len, flags); - } - - /* First we try non-blocking. */ - ret = tdb_brlock(tdb, ltype, off, len, nb_flags); - if (ret == 0) { - return 0; - } - - /* Try locking first half, then second. */ - ret = tdb_chainlock_gradual(tdb, ltype, flags, off, len / 2); - if (ret == -1) - return -1; - - ret = tdb_chainlock_gradual(tdb, ltype, flags, - off + len / 2, len - len / 2); - if (ret == -1) { - tdb_brunlock(tdb, ltype, off, len / 2); - return -1; - } - return 0; -} - -/* lock/unlock entire database. It can only be upgradable if you have some - * other way of guaranteeing exclusivity (ie. transaction write lock). - * We do the locking gradually to avoid being starved by smaller locks. */ -int tdb_allrecord_lock(struct tdb_context *tdb, int ltype, - enum tdb_lock_flags flags, bool upgradable) -{ - switch (tdb_allrecord_check(tdb, ltype, flags, upgradable)) { - case -1: - return -1; - case 0: - return 0; - } - - /* We cover two kinds of locks: - * 1) Normal chain locks. Taken for almost all operations. - * 3) Individual records locks. Taken after normal or free - * chain locks. - * - * It is (1) which cause the starvation problem, so we're only - * gradual for that. */ - if (tdb_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP, - tdb->header.hash_size * 4) == -1) { - return -1; - } - - /* Grab individual record locks. */ - if (tdb_brlock(tdb, ltype, lock_offset(tdb->header.hash_size), 0, - flags) == -1) { - tdb_brunlock(tdb, ltype, FREELIST_TOP, - tdb->header.hash_size * 4); - return -1; - } - - tdb->allrecord_lock.count = 1; - /* If it's upgradable, it's actually exclusive so we can treat - * it as a write lock. */ - tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype; - tdb->allrecord_lock.off = upgradable; - - if (tdb_needs_recovery(tdb)) { - bool mark = flags & TDB_LOCK_MARK_ONLY; - tdb_allrecord_unlock(tdb, ltype, mark); - if (mark) { - tdb->ecode = TDB_ERR_LOCK; - TDB_LOG((tdb, TDB_DEBUG_ERROR, - "tdb_lockall_mark cannot do recovery\n")); - return -1; - } - if (tdb_lock_and_recover(tdb) == -1) { - return -1; - } - return tdb_allrecord_lock(tdb, ltype, flags, upgradable); - } - - return 0; -} - - - -/* unlock entire db */ -int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype, bool mark_lock) -{ - /* There are no locks on read-only dbs */ - if (tdb->read_only || tdb->traverse_read) { - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - if (tdb->allrecord_lock.count == 0) { - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - /* Upgradable locks are marked as write locks. */ - if (tdb->allrecord_lock.ltype != ltype - && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) { - tdb->ecode = TDB_ERR_LOCK; - return -1; - } - - if (tdb->allrecord_lock.count > 1) { - tdb->allrecord_lock.count--; - return 0; - } - - if (!mark_lock && tdb_brunlock(tdb, ltype, FREELIST_TOP, 0)) { - TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno))); - return -1; - } - - tdb->allrecord_lock.count = 0; - tdb->allrecord_lock.ltype = 0; - - return 0; -} - -/* lock entire database with write lock */ -int tdb_lockall(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_lockall"); - return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false); -} - -/* lock entire database with write lock - mark only */ -int tdb_lockall_mark(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_lockall_mark"); - return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY, false); -} - -/* unlock entire database with write lock - unmark only */ -int tdb_lockall_unmark(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_lockall_unmark"); - return tdb_allrecord_unlock(tdb, F_WRLCK, true); -} - -/* lock entire database with write lock - nonblocking varient */ -int tdb_lockall_nonblock(struct tdb_context *tdb) -{ - int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false); - tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret); - return ret; -} - -/* unlock entire database with write lock */ -int tdb_unlockall(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_unlockall"); - return tdb_allrecord_unlock(tdb, F_WRLCK, false); -} - -/* lock entire database with read lock */ -int tdb_lockall_read(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_lockall_read"); - return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false); -} - -/* lock entire database with read lock - nonblock varient */ -int tdb_lockall_read_nonblock(struct tdb_context *tdb) -{ - int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false); - tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret); - return ret; -} - -/* unlock entire database with read lock */ -int tdb_unlockall_read(struct tdb_context *tdb) -{ - tdb_trace(tdb, "tdb_unlockall_read"); - return tdb_allrecord_unlock(tdb, F_RDLCK, false); -} - -/* 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) -{ - int ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); - tdb_trace_1rec(tdb, "tdb_chainlock", key); - return ret; -} - -/* 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) -{ - int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); - tdb_trace_1rec_ret(tdb, "tdb_chainlock_nonblock", key, ret); - return ret; -} - -/* 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) -{ - int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))), - F_WRLCK, TDB_LOCK_MARK_ONLY); - tdb_trace_1rec(tdb, "tdb_chainlock_mark", key); - return ret; -} - -/* 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) -{ - tdb_trace_1rec(tdb, "tdb_chainlock_unmark", key); - return tdb_nest_unlock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))), - F_WRLCK, true); -} - -int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key) -{ - tdb_trace_1rec(tdb, "tdb_chainunlock", key); - return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); -} - -int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key) -{ - int ret; - ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK); - tdb_trace_1rec(tdb, "tdb_chainlock_read", key); - return ret; -} - -int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key) -{ - tdb_trace_1rec(tdb, "tdb_chainunlock_read", 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->allrecord_lock.count) { - return 0; - } - return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 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; - if (tdb->allrecord_lock.count) { - if (tdb->allrecord_lock.ltype == F_WRLCK) { - return 0; - } - return -1; - } - return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE); -} - -int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off) -{ - if (tdb->allrecord_lock.count) { - return 0; - } - return tdb_brunlock(tdb, F_WRLCK, off, 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->allrecord_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_brunlock(tdb, F_RDLCK, off, 1) : 0); -} - -bool tdb_have_extra_locks(struct tdb_context *tdb) -{ - unsigned int extra = tdb->num_lockrecs; - - /* A transaction holds the lock for all records. */ - if (!tdb->transaction && tdb->allrecord_lock.count) { - return true; - } - - /* We always hold the active lock if CLEAR_IF_FIRST. */ - if (find_nestlock(tdb, ACTIVE_LOCK)) { - extra--; - } - - /* In a transaction, we expect to hold the transaction lock */ - if (tdb->transaction && find_nestlock(tdb, TRANSACTION_LOCK)) { - extra--; - } - - return extra; -} - -/* The transaction code uses this to remove all locks. */ -void tdb_release_transaction_locks(struct tdb_context *tdb) -{ - unsigned int i, active = 0; - - if (tdb->allrecord_lock.count != 0) { - tdb_brunlock(tdb, tdb->allrecord_lock.ltype, FREELIST_TOP, 0); - tdb->allrecord_lock.count = 0; - } - - for (i=0;i<tdb->num_lockrecs;i++) { - struct tdb_lock_type *lck = &tdb->lockrecs[i]; - - /* Don't release the active lock! Copy it to first entry. */ - if (lck->off == ACTIVE_LOCK) { - tdb->lockrecs[active++] = *lck; - } else { - tdb_brunlock(tdb, lck->ltype, lck->off, 1); - } - } - tdb->num_lockrecs = active; - if (tdb->num_lockrecs == 0) { - SAFE_FREE(tdb->lockrecs); - } -} |