Index: ext/lsm1/lsm_shared.c
==================================================================
--- ext/lsm1/lsm_shared.c
+++ ext/lsm1/lsm_shared.c
@@ -250,10 +250,12 @@
   }else{
     /* Block for an exclusive lock on DMS1. This lock serializes all calls
     ** to doDbConnect() and doDbDisconnect() across all processes.  */
     rc = lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_EXCL, 1);
     if( rc==LSM_OK ){
+
+      lsmShmLock(pDb, LSM_LOCK_DMS2, LSM_LOCK_UNLOCK, 0);
 
       /* Try an exclusive lock on DMS2. If successful, this is the last
       ** connection to the database. In this case flush the contents of the
       ** in-memory tree to disk and write a checkpoint.  */
       rc = lsmShmTestLock(pDb, LSM_LOCK_DMS2, 1, LSM_LOCK_EXCL);
@@ -322,11 +324,10 @@
     if( pDb->iRwclient>=0 ){
       lsmShmLock(pDb, LSM_LOCK_RWCLIENT(pDb->iRwclient), LSM_LOCK_UNLOCK, 0);
       pDb->iRwclient = -1;
     }
 
-    lsmShmLock(pDb, LSM_LOCK_DMS2, LSM_LOCK_UNLOCK, 0);
     lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_UNLOCK, 0);
   }
   pDb->pShmhdr = 0;
 }
 
@@ -475,12 +476,19 @@
         int bReadonly = (pDb->bReadonly && pDb->bMultiProc);
         rc = dbOpenSharedFd(pDb->pEnv, p, bReadonly);
       }
 
       if( rc==LSM_OK && p->bMultiProc==0 ){
+        /* Hold an exclusive lock DMS1 while grabbing DMS2. This ensures
+        ** that any ongoing call to doDbDisconnect() (even one in another
+        ** process) is finished before proceeding.  */
         assert( p->bReadonly==0 );
-        rc = lsmEnvLock(pDb->pEnv, p->pFile, LSM_LOCK_DMS2, LSM_LOCK_EXCL);
+        rc = lsmEnvLock(pDb->pEnv, p->pFile, LSM_LOCK_DMS1, LSM_LOCK_EXCL);
+        if( rc==LSM_OK ){
+          rc = lsmEnvLock(pDb->pEnv, p->pFile, LSM_LOCK_DMS2, LSM_LOCK_EXCL);
+          lsmEnvLock(pDb->pEnv, p->pFile, LSM_LOCK_DMS1, LSM_LOCK_UNLOCK);
+        }
       }
 
       if( rc==LSM_OK ){
         p->pDbNext = gShared.pDatabase;
         gShared.pDatabase = p;
@@ -1745,11 +1753,14 @@
     if( eOp==LSM_LOCK_EXCL ) mask |= ((u64)1 << (iLock+32-1));
   }
 
   lsmMutexEnter(db->pEnv, p->pClientMutex);
   for(pIter=p->pConn; pIter; pIter=pIter->pNext){
-    if( pIter!=db && (pIter->mLock & mask) ) break;
+    if( pIter!=db && (pIter->mLock & mask) ){
+      assert( pIter!=db );
+      break;
+    }
   }
 
   if( pIter ){
     rc = LSM_BUSY;
   }else if( p->bMultiProc ){