s/MDB_NORDLOCK/MDB_NOLOCK/

Leave all lock management to the caller.

diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h
index 968862f987d692b90569323af4e0948adcba3e6b..8cdac26b062296fc19de1a96b524bb0b715c5162 100644 (file)
--- a/libraries/liblmdb/lmdb.h
+++ b/libraries/liblmdb/lmdb.h
@@ -269,8 +269,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel
 #define MDB_MAPASYNC           0x100000
        /** tie reader locktable slots to #MDB_txn objects instead of to threads */
 #define MDB_NOTLS              0x200000
-       /** for #MDB_RDONLY env, don't use reader locktable, caller must manage read/write concurrency */
-#define MDB_NORDLOCK           0x400000
+       /** don't do any locking, caller must manage their own locks */
+#define MDB_NOLOCK             0x400000
 /** @} */
 
 /**    @defgroup       mdb_dbi_open    Database Flags
@@ -527,11 +527,13 @@ int  mdb_env_create(MDB_env **env);
         *              user threads over individual OS threads need this option. Such an
         *              application must also serialize the write transactions in an OS
         *              thread, since MDB's write locking is unaware of the user threads.
-        *      <li>#MDB_NORDLOCK
-        *              Don't use the reader locktable at all. This flag is only valid
-        *              with #MDB_RDONLY. MDB will use no read locks. If other processes
-        *              may be opening the environment with write access, the callers
-        *              must manage read/write locks themselves.
+        *      <li>#MDB_NOLOCK
+        *              Don't do any locking. If concurrent access is anticipated, the
+        *              caller must manage all concurrency itself. For proper operation
+        *              the caller must enforce single-writer semantics, and must ensure
+        *              that no readers are using old transactions while a writer is
+        *              active. The simplest approach is to use an exclusive lock so that
+        *              no readers may be active at all when a writer begins.
         * </ul>
         * @param[in] mode The UNIX permissions to set on created files. This parameter
         * is ignored on Windows.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 637cd08809eedcc556d2ecff6eec23ffd3a06b8e..30b562c43e6c2d64b4c43303677f073566b2026b 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -425,7 +425,8 @@ typedef uint16_t     indx_t;
  *
  *     If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
  *
- *     No reader table is used if the database is on a read-only filesystem.
+ *     No reader table is used if the database is on a read-only filesystem, or
+ *     if #MDB_NOLOCK is set.
  *
  *     Since the database uses multi-version concurrency control, readers don't
  *     actually need any locking. This table is used to keep track of which
@@ -1572,12 +1573,14 @@ mdb_find_oldest(MDB_txn *txn)
 {
        int i;
        txnid_t mr, oldest = txn->mt_txnid - 1;
-       MDB_reader *r = txn->mt_env->me_txns->mti_readers;
-       for (i = txn->mt_env->me_txns->mti_numreaders; --i >= 0; ) {
-               if (r[i].mr_pid) {
-                       mr = r[i].mr_txnid;
-                       if (oldest > mr)
-                               oldest = mr;
+       if (txn->mt_env->me_txns) {
+               MDB_reader *r = txn->mt_env->me_txns->mti_readers;
+               for (i = txn->mt_env->me_txns->mti_numreaders; --i >= 0; ) {
+                       if (r[i].mr_pid) {
+                               mr = r[i].mr_txnid;
+                               if (oldest > mr)
+                                       oldest = mr;
+                       }
                }
        }
        return oldest;
@@ -2174,10 +2177,15 @@ mdb_txn_renew0(MDB_txn *txn)
                        meta = env->me_metas[txn->mt_txnid & 1];
                }
        } else {
-               LOCK_MUTEX_W(env);
+               if (env->me_txns) {
+                       LOCK_MUTEX_W(env);
 
-               txn->mt_txnid = env->me_txns->mti_txnid;
-               meta = env->me_metas[txn->mt_txnid & 1];
+                       txn->mt_txnid = env->me_txns->mti_txnid;
+                       meta = env->me_metas[txn->mt_txnid & 1];
+               } else {
+                       meta = env->me_metas[ mdb_env_pick_meta(env) ];
+                       txn->mt_txnid = meta->mm_txnid;
+               }
                txn->mt_txnid++;
 #if MDB_DEBUG
                if (txn->mt_txnid == mdb_debug_start)
@@ -2417,7 +2425,8 @@ mdb_txn_reset0(MDB_txn *txn, const char *act)
 
                env->me_txn = NULL;
                /* The writer mutex was locked in mdb_txn_begin. */
-               UNLOCK_MUTEX_W(env);
+               if (env->me_txns)
+                       UNLOCK_MUTEX_W(env);
        }
 }
 
@@ -2934,7 +2943,8 @@ done:
        env->me_txn = NULL;
        mdb_dbis_update(txn, 1);
 
-       UNLOCK_MUTEX_W(env);
+       if (env->me_txns)
+               UNLOCK_MUTEX_W(env);
        free(txn);
 
        return MDB_SUCCESS;
@@ -3180,7 +3190,8 @@ done:
         * readers will get consistent data regardless of how fresh or
         * how stale their view of these values is.
         */
-       env->me_txns->mti_txnid = txn->mt_txnid;
+       if (env->me_txns)
+               env->me_txns->mti_txnid = txn->mt_txnid;
 
        return MDB_SUCCESS;
 }
@@ -3900,7 +3911,7 @@ fail:
         *      environment and re-opening it with the new flags.
         */
 #define        CHANGEABLE      (MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC)
-#define        CHANGELESS      (MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP|MDB_NOTLS|MDB_NORDLOCK)
+#define        CHANGELESS      (MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK)
 
 int
 mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode)
@@ -3953,7 +3964,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
        }
 
        /* For RDONLY, get lockfile after we know datafile exists */
-       if (!F_ISSET(flags, MDB_RDONLY)) {
+       if (!(flags & (MDB_RDONLY|MDB_NOLOCK))) {
                rc = mdb_env_setup_locks(env, lpath, mode, &excl);
                if (rc)
                        goto leave;
@@ -3983,7 +3994,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
                goto leave;
        }
 
-       if ((flags & (MDB_RDONLY|MDB_NORDLOCK)) == MDB_RDONLY) {
+       if ((flags & (MDB_RDONLY|MDB_NOLOCK)) == MDB_RDONLY) {
                rc = mdb_env_setup_locks(env, lpath, mode, &excl);
                if (rc)
                        goto leave;