Use std::unique_lock<std::mutex> to guard data set.

11 files changed, 140 insertions, 145 deletions

diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.cpp
index 0374ac52b65..b4907627894 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.cpp
@@ -141,9 +141,8 @@ FastS_DataSetBase::SetActiveQuery_HasLock()
 void
 FastS_DataSetBase::SetActiveQuery()
 {
-    LockDataset();
+    auto dsGuard(getDsGuard());
     SetActiveQuery_HasLock();
-    UnlockDataset();
 }
 
 
@@ -160,9 +159,8 @@ FastS_DataSetBase::ClearActiveQuery_HasLock(FastS_TimeKeeper *timeKeeper)
 void
 FastS_DataSetBase::ClearActiveQuery(FastS_TimeKeeper *timeKeeper)
 {
-    LockDataset();
+    auto dsGuard(getDsGuard());
     ClearActiveQuery_HasLock(timeKeeper);
-    UnlockDataset();
 }
 
 
@@ -272,7 +270,7 @@ FastS_DataSetBase::UpdateSearchTime(double tnow,
                                     double elapsed, bool timedout)
 {
     int slot;
-    LockDataset();
+    auto dsGuard(getDsGuard());
     slot = (int) (elapsed * 10);
     if (slot >= _total._timestatslots)
         slot = _total._timestatslots - 1;
@@ -280,7 +278,6 @@ FastS_DataSetBase::UpdateSearchTime(double tnow,
         slot = 0;
     _total._timestats[slot]++;
     _total._normalTimeStat.Update(tnow, elapsed, timedout);
-    UnlockDataset();
 }
 
 
@@ -302,7 +299,7 @@ void
 FastS_DataSetBase::addPerformance(FastS_QueryPerf &qp)
 {
     FastS_TimeStatTotals totals;
-    LockDataset();
+    auto dsGuard(getDsGuard());
     _total._normalTimeStat.AddTotal(&totals);
     qp.queueLen   += _queryQueue.GetQueueLen();
     qp.activeCnt  += _queryQueue.GetActiveQueries();
@@ -310,7 +307,6 @@ FastS_DataSetBase::addPerformance(FastS_QueryPerf &qp)
     qp.queryTime  += totals._totalAccTime;
     qp.dropCnt    += _total._nOverload;
     qp.timeoutCnt += _total._nTimedOut;
-    UnlockDataset();
 }
 
 
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.h b/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.h
index 75c47fffc27..a757d92fdeb 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/dataset_base.h
@@ -8,6 +8,7 @@
 #include <atomic>
 #include <vespa/fastos/time.h>
 #include <vespa/fastos/cond.h>
+#include <mutex>
 
 class FastS_TimeKeeper;
 
@@ -164,7 +165,7 @@ public:
 
 protected:
     FastS_AppContext *_appCtx;
-    FastOS_Mutex  _lock;
+    std::mutex   _lock;
     FastOS_Time  _createtime;
     queryQueue_t _queryQueue;
     total_t      _total;
@@ -182,9 +183,7 @@ public:
 
     // locking stuff
     //--------------
-    void LockDataset()   { _lock.Lock();   }
-    void UnlockDataset() { _lock.Unlock(); }
-    FastOS_Mutex & getMutex() { return _lock; }
+    std::unique_lock<std::mutex> getDsGuard() { return std::unique_lock<std::mutex>(_lock); }
 
     // query queue related methods
     //----------------------------
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/datasetcollection.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/datasetcollection.cpp
index 95ef4899646..cf7cd21d9b9 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/datasetcollection.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/datasetcollection.cpp
@@ -229,9 +229,10 @@ FastS_DataSetCollection::CreateSearch(uint32_t dataSetID,
         ret = new FastS_FailedSearch(dataSetID, false,
                                      search::engine::ECODE_ILLEGAL_DATASET, NULL);
     } else {
-        dataset->LockDataset();
-        dataset->SetActiveQuery_HasLock();
-        dataset->UnlockDataset();
+        {
+            auto dsGuard(dataset->getDsGuard());
+            dataset->SetActiveQuery_HasLock();
+        }
         /* XXX: Semantic change: precounted as active in dataset */
         ret = dataset->CreateSearch(this, timeKeeper, /* async = */ false);
     }
@@ -247,9 +248,8 @@ FastS_DataSetCollection::CheckQueryQueues(FastS_TimeKeeper *timeKeeper)
         FastS_DataSetBase *dataset = PeekDataSet(datasetidx);
 
         if (dataset != NULL) {
-            dataset->LockDataset();
+            auto dsGuard(dataset->getDsGuard());
             dataset->CheckQueryQueue_HasLock(timeKeeper);
-            dataset->UnlockDataset();
         }
     }
 }
@@ -262,9 +262,8 @@ FastS_DataSetCollection::AbortQueryQueues()
         FastS_DataSetBase *dataset = PeekDataSet(datasetidx);
 
         if (dataset != NULL) {
-            dataset->LockDataset();
+            auto dsGuard(dataset->getDsGuard());
             dataset->AbortQueryQueue_HasLock();
-            dataset->UnlockDataset();
         }
     }
 }
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/engine_base.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/engine_base.cpp
index 83ec3d73b11..1863b2f20e5 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/engine_base.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/engine_base.cpp
@@ -337,28 +337,29 @@ FastS_EngineBase::HandlePingResponse(uint32_t partid,
         }
     }
 
-    _dataset->LockDataset();
-    if (changed)
-        _dataset->LinkOutPart_HasLock(this);
+    {
+        auto dsGuard(_dataset->getDsGuard());
+        if (changed)
+            _dataset->LinkOutPart_HasLock(this);
 
-    _partid             = partid;
-    if (docstamp != _reported._docstamp) {
-        _reported._docstamp = docstamp;
-    }
-    _reported._mld      = mld;
-    _reported._maxNodes = maxnodes;
-    _reported._actNodes = nodes;
-    _reported._maxParts = maxparts;
-    _reported._actParts = parts;
-    if (_reported._activeDocs != activeDocs) {
-        _dataset->updateActiveDocs_HasLock(GetConfRowID(), activeDocs, _reported._activeDocs);
-        _reported._activeDocs = activeDocs;
-    }
-    _isUp               = true;
+        _partid             = partid;
+        if (docstamp != _reported._docstamp) {
+            _reported._docstamp = docstamp;
+        }
+        _reported._mld      = mld;
+        _reported._maxNodes = maxnodes;
+        _reported._actNodes = nodes;
+        _reported._maxParts = maxparts;
+        _reported._actParts = parts;
+        if (_reported._activeDocs != activeDocs) {
+            _dataset->updateActiveDocs_HasLock(GetConfRowID(), activeDocs, _reported._activeDocs);
+            _reported._activeDocs = activeDocs;
+        }
+        _isUp               = true;
 
-    _dataset->LinkInPart_HasLock(this);
+        _dataset->LinkInPart_HasLock(this);
 
-    _dataset->UnlockDataset();
+    }
     _dataset->ScheduleCheckTempFail();
 
     if (onlined) {
@@ -383,13 +384,14 @@ FastS_EngineBase::HandleLostConnection()
         _stats._floptime.SetNow();
         LOG(warning, "Search node %s down", _config._name);
 
-        _dataset->LockDataset();
-        _dataset->LinkOutPart_HasLock(this);
-        PossCount noDocs;
-        noDocs.valid = true;
-        _dataset->updateActiveDocs_HasLock(GetConfRowID(), noDocs, _reported._activeDocs);
-        _reported._activeDocs = noDocs;
-        _dataset->UnlockDataset();
+        {
+            auto dsGuard(_dataset->getDsGuard());
+            _dataset->LinkOutPart_HasLock(this);
+            PossCount noDocs;
+            noDocs.valid = true;
+            _dataset->updateActiveDocs_HasLock(GetConfRowID(), noDocs, _reported._activeDocs);
+            _reported._activeDocs = noDocs;
+        }
         _dataset->ScheduleCheckTempFail();
         HandleDown(); // classic: NotifyVirtualConnsDown
     }
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_dataset.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_dataset.cpp
index 92ef41cc636..f6fb46a67ca 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_dataset.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_dataset.cpp
@@ -108,7 +108,7 @@ FastS_FNET_DataSet::Free()
 bool
 FastS_FNET_DataSet::isGoodRow(uint32_t rowId)
 {
-    LockDataset();
+    auto dsGuard(getDsGuard());
     uint64_t rowBit = 1ul << rowId;
     bool wasBad = ((_failedRowsBitmask & rowBit) != 0);
     bool isBad = false;
@@ -146,6 +146,5 @@ FastS_FNET_DataSet::isGoodRow(uint32_t rowId)
         LOG(info, "Row %d is now good again (%lu/%g active docs, coverage %ld/%ld)",
             rowId, candDocs, restAvg, nodesUp, configuredParts);
     }
-    UnlockDataset();
     return !isBad;
 }
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.cpp
index 5b444427c4d..8cfd49e4108 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.cpp
@@ -64,10 +64,12 @@ FastS_FNET_Engine::Connect()
             _transport->Connect(_spec.c_str(),
                                 &FS4PersistentPacketStreamer::Instance,
                                 this);
-        LockDataSet();
-        FNET_Connection *oldConn = _conn;
-        _conn = newConn;
-        UnlockDataSet();
+        FNET_Connection *oldConn;
+        {
+            auto dsGuard(getDsGuard());
+            oldConn = _conn;
+            _conn = newConn;
+        }
         if (oldConn != NULL)
             oldConn->SubRef();
         if (newConn == NULL && !IsRealBad())
@@ -81,10 +83,12 @@ FastS_FNET_Engine::Disconnect()
 {
     if (_conn != NULL) {
         _conn->CloseAdminChannel();
-        LockDataSet();
-        FNET_Connection *conn = _conn;
-        _conn = NULL;
-        UnlockDataSet();
+        FNET_Connection *conn;
+        {
+            auto dsGuard(getDsGuard());
+            conn = _conn;
+            _conn = NULL;
+        }
         _transport->Close(conn, /* needref = */ false);
     }
 }
@@ -116,9 +120,8 @@ FastS_FNET_Engine::~FastS_FNET_Engine()
     _connectTask.Kill();
     Disconnect();
     if (IsUp()) {
-        LockDataSet();
+        auto dsGuard(getDsGuard());
         _dataset->LinkOutPart_HasLock(this);
-        UnlockDataSet();
     }
     if (_monitorQuery != NULL) {
         _monitorQuery->Free();
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.h b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.h
index 9f03f0319db..bd40229180d 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_engine.h
@@ -95,8 +95,7 @@ public:
                       FastS_FNET_DataSet *dataset);
     virtual ~FastS_FNET_Engine();
 
-    void LockDataSet()   { _dataset->LockDataset();   }
-    void UnlockDataSet() { _dataset->UnlockDataset(); }
+    std::unique_lock<std::mutex> getDsGuard() { return _dataset->getDsGuard(); }
 
     void StartWarnTimer();
     void ScheduleConnect(double delay);
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.cpp
index c5e3d001210..6beaf22a238 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.cpp
@@ -103,11 +103,11 @@ FastS_FNET_SearchNode::NT_InitMerge(uint32_t *numDocs,
 
 
 FastS_EngineBase *
-FastS_FNET_SearchNode::getPartition(const FastOS_Mutex & dsMutex, bool userow, FastS_FNET_DataSet *dataset)
+FastS_FNET_SearchNode::getPartition(const std::unique_lock<std::mutex> &dsGuard, bool userow, FastS_FNET_DataSet *dataset)
 {
     return ((userow)
-        ? dataset->getPartitionMLD(dsMutex, getPartID(), _flags._docsumMld, _docsumRow)
-        : dataset->getPartitionMLD(dsMutex, getPartID(), _flags._docsumMld));
+        ? dataset->getPartitionMLD(dsGuard, getPartID(), _flags._docsumMld, _docsumRow)
+        : dataset->getPartitionMLD(dsGuard, getPartID(), _flags._docsumMld));
 }
 
 
@@ -335,26 +335,26 @@ FastS_FNET_Search::ConnectQueryNodes()
     }
     EngineNodeMap engines;
     engines.reserve(_nodes.size());
-    FastOS_Mutex & dsLock = _dataset->getMutex();
-    dsLock.Lock();
-    for (uint32_t i = 0; i < _nodes.size(); i++) {
-        FastS_EngineBase *engine = NULL;
-        if (_dataset->useFixedRowDistribution()) {
-            engine = _dataset->getPartition(dsLock, i, fixedRow);
-            LOG(debug, "FixedRow: getPartition(part=%u, row=%u) -> engine(%s)", i, fixedRow, (engine != nullptr ? engine->GetName() : "null"));
-        } else {
-            engine = _dataset->getPartition(dsLock, i);
-        }
-        if (engine != nullptr) {
-            LOG(debug, "Wanted part=%d, engine={name=%s, row=%d, partid=%d}", i, engine->GetName(), engine->GetConfRowID(), engine->GetPartID());
+    {
+        auto dsGuard(_dataset->getDsGuard());
+        for (uint32_t i = 0; i < _nodes.size(); i++) {
+            FastS_EngineBase *engine = NULL;
+            if (_dataset->useFixedRowDistribution()) {
+                engine = _dataset->getPartition(dsGuard, i, fixedRow);
+                LOG(debug, "FixedRow: getPartition(part=%u, row=%u) -> engine(%s)", i, fixedRow, (engine != nullptr ? engine->GetName() : "null"));
+            } else {
+                engine = _dataset->getPartition(dsGuard, i);
+            }
             if (engine != nullptr) {
-                engines.emplace_back(engine, getNode(i));
+                LOG(debug, "Wanted part=%d, engine={name=%s, row=%d, partid=%d}", i, engine->GetName(), engine->GetConfRowID(), engine->GetPartID());
+                if (engine != nullptr) {
+                    engines.emplace_back(engine, getNode(i));
+                }
+            } else {
+                LOG(debug, "No engine for part %d", i);
             }
-        } else {
-            LOG(debug, "No engine for part %d", i);
         }
     }
-    dsLock.Unlock();
     connectNodes(engines);
 }
 
@@ -370,19 +370,19 @@ FastS_FNET_Search::ConnectEstimateNodes()
     uint32_t partcnt = 0;
 
     EngineNodeMap engines;
-    FastOS_Mutex & dsLock = _dataset->getMutex();
-    dsLock.Lock();
-    while (partcnt < _dataset->GetEstimateParts() && trycnt < _estPartCutoff) {
-        FastS_EngineBase *engine = _dataset->getPartition(dsLock, partid);
-        if (engine != NULL) {
-            engines.emplace_back(engine, getNode(partid));
-            partcnt++;
+    {
+        auto dsGuard(_dataset->getDsGuard());
+        while (partcnt < _dataset->GetEstimateParts() && trycnt < _estPartCutoff) {
+            FastS_EngineBase *engine = _dataset->getPartition(dsGuard, partid);
+            if (engine != NULL) {
+                engines.emplace_back(engine, getNode(partid));
+                partcnt++;
+            }
+            trycnt++;
+            partid = (partid + 1) % _estPartCutoff;
         }
-        trycnt++;
-        partid = (partid + 1) % _estPartCutoff;
+        _estParts = partcnt;
     }
-    _estParts = partcnt;
-    dsLock.Unlock();
     connectNodes(engines);
 }
 
@@ -394,11 +394,10 @@ void FastS_FNET_SearchNode::Connect(FastS_FNET_Engine *engine)
 
     _engine = engine;
     _flags._needSubCost = true;
-    _engine->LockDataSet();
+    auto dsGuard(_engine->getDsGuard());
     _channel = _engine->OpenChannel_HasDSLock(this);
     _rowid   = _engine->GetConfRowID();
     _stamp   = _engine->GetTimeStamp();
-    _engine->UnlockDataSet();
 }
 
 void FastS_FNET_SearchNode::Connect_HasDSLock(FastS_FNET_Engine *engine)
@@ -434,30 +433,30 @@ void FastS_FNET_Search::connectSearchPath(const SearchPath::Element &elem,
                                           uint32_t dispatchLevel)
 {
     EngineNodeMap engines;
-    FastOS_Mutex & dsLock = _dataset->getMutex();
-    dsLock.Lock();
-    if (!elem.hasRow()) {
-        for (size_t partId : elem.nodes()) {
-            if (partId < _nodes.size()) {
-                FastS_EngineBase *engine = _dataset->getPartition(dsLock, partId);
-                LOG(debug, "searchpath='%s', partId=%ld, dispatchLevel=%u", spec.c_str(), partId, dispatchLevel);
-                if (engine != NULL) {
-                    engines.emplace_back(engine, getNode(partId));
+    {
+        auto dsGuard(_dataset->getDsGuard());
+        if (!elem.hasRow()) {
+            for (size_t partId : elem.nodes()) {
+                if (partId < _nodes.size()) {
+                    FastS_EngineBase *engine = _dataset->getPartition(dsGuard, partId);
+                    LOG(debug, "searchpath='%s', partId=%ld, dispatchLevel=%u", spec.c_str(), partId, dispatchLevel);
+                    if (engine != NULL) {
+                        engines.emplace_back(engine, getNode(partId));
+                    }
                 }
             }
-        }
-    } else {
-        for (size_t partId : elem.nodes()) {
-            if (partId < _nodes.size()) {
-                FastS_EngineBase *engine = _dataset->getPartition(dsLock, partId, elem.row());
-                LOG(debug, "searchpath='%s', partId=%ld, row=%ld, dispatchLevel=%u", spec.c_str(), partId, elem.row(), dispatchLevel);
-                if (engine != NULL) {
-                    engines.emplace_back(engine, getNode(partId));
+        } else {
+            for (size_t partId : elem.nodes()) {
+                if (partId < _nodes.size()) {
+                    FastS_EngineBase *engine = _dataset->getPartition(dsGuard, partId, elem.row());
+                    LOG(debug, "searchpath='%s', partId=%ld, row=%ld, dispatchLevel=%u", spec.c_str(), partId, elem.row(), dispatchLevel);
+                    if (engine != NULL) {
+                        engines.emplace_back(engine, getNode(partId));
+                    }
                 }
             }
         }
     }
-    dsLock.Unlock();
     connectNodes(engines);
 }
 
@@ -471,26 +470,26 @@ FastS_FNET_Search::ConnectDocsumNodes(bool ignoreRow)
     bool userow = (_dataset->GetRowBits() > 0) && !ignoreRow;
 
     EngineNodeMap engines;
-    FastOS_Mutex & dsLock = _dataset->getMutex();
-    dsLock.Lock();
-    for (auto & node : _nodes) {
-        if (node._gdx != NULL) {
-            FastS_EngineBase *engine = node.getPartition(dsLock, userow, _dataset);
-            if (engine != nullptr) {
-                engines.emplace_back(engine, &node);
-            }
-        }
-        for (FastS_FNET_SearchNode::ExtraDocsumNodesIter iter(&node); iter.valid(); ++iter) {
-            FastS_FNET_SearchNode *eNode = *iter;
-            if (eNode->_gdx != NULL) {
-                FastS_EngineBase *engine = eNode->getPartition(dsLock, userow, _dataset);
+    {
+        auto dsGuard(_dataset->getDsGuard());
+        for (auto & node : _nodes) {
+            if (node._gdx != NULL) {
+                FastS_EngineBase *engine = node.getPartition(dsGuard, userow, _dataset);
                 if (engine != nullptr) {
-                    engines.emplace_back(engine, eNode);
+                    engines.emplace_back(engine, &node);
+                }
+            }
+            for (FastS_FNET_SearchNode::ExtraDocsumNodesIter iter(&node); iter.valid(); ++iter) {
+                FastS_FNET_SearchNode *eNode = *iter;
+                if (eNode->_gdx != NULL) {
+                    FastS_EngineBase *engine = eNode->getPartition(dsGuard, userow, _dataset);
+                    if (engine != nullptr) {
+                        engines.emplace_back(engine, eNode);
+                    }
                 }
             }
         }
     }
-    dsLock.Unlock();
     connectNodes(engines);
 }
 
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.h b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.h
index 3f9fc3db077..de913bda46f 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/fnet_search.h
@@ -112,7 +112,7 @@ public:
     bool IsConnected() const { return _channel != NULL; }
     void Connect(FastS_FNET_Engine *engine);
     void Connect_HasDSLock(FastS_FNET_Engine *engine);
-    FastS_EngineBase * getPartition(const FastOS_Mutex & dsMutex, bool userow, FastS_FNET_DataSet *dataset);
+    FastS_EngineBase * getPartition(const std::unique_lock<std::mutex> &dsGuard, bool userow, FastS_FNET_DataSet *dataset);
     void allocGDX(search::docsummary::GetDocsumArgs *args, const search::engine::PropertiesMap &properties);
     void postGDX(uint32_t *pendingDocsums, uint32_t *pendingDocsumNodes);
     vespalib::string toString() const;
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
index 1d3c26b8e57..aa1a783a7be 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
@@ -241,13 +241,12 @@ FastS_PlainDataSet::~FastS_PlainDataSet()
 void
 FastS_PlainDataSet::UpdateMaxHitsPerNodeLog(bool incomplete, bool fuzzy)
 {
-    LockDataset();
+    auto dsGuard(getDsGuard());
     _MHPN_log._cnt++;
     if (incomplete)
         _MHPN_log._incompleteCnt++;
     if (fuzzy)
         _MHPN_log._fuzzyCnt++;
-    UnlockDataset();
 }
 
 
@@ -272,9 +271,8 @@ FastS_PlainDataSet::RefCostUseNewEngine(FastS_EngineBase *oldEngine,
 void
 FastS_PlainDataSet::updateSearchTime(double searchTime, uint32_t rowId)
 {
-    LockDataset();
+    auto dsGuard(getDsGuard());
     _stateOfRows.updateSearchTime(searchTime, rowId);
-    UnlockDataset();
 }
 
 uint32_t
@@ -316,9 +314,9 @@ FastS_PlainDataSet::UseNewEngine(FastS_EngineBase *oldEngine,
 }
 
 FastS_EngineBase *
-FastS_PlainDataSet::getPartition(const FastOS_Mutex & dsMutex, uint32_t partindex, uint32_t rowid)
+FastS_PlainDataSet::getPartition(const std::unique_lock<std::mutex> &dsGuard, uint32_t partindex, uint32_t rowid)
 {
-    (void) dsMutex;
+    (void) dsGuard;
     FastS_EngineBase*  ret = NULL;
 
     if (IsValidPartIndex_HasLock(partindex)) {
@@ -365,9 +363,9 @@ FastS_PlainDataSet::countNodesUpInRow_HasLock(uint32_t rowid)
 }
 
 FastS_EngineBase *
-FastS_PlainDataSet::getPartition(const FastOS_Mutex & dsMutex, uint32_t partindex)
+FastS_PlainDataSet::getPartition(const std::unique_lock<std::mutex> &dsGuard, uint32_t partindex)
 {
-    (void) dsMutex;
+    (void) dsGuard;
     FastS_EngineBase*  ret = NULL;
     unsigned int oldCount = 1;
     unsigned int engineCount = 0;
@@ -400,9 +398,9 @@ FastS_PlainDataSet::getPartition(const FastOS_Mutex & dsMutex, uint32_t partinde
 }
 
 FastS_EngineBase *
-FastS_PlainDataSet::getPartitionMLD(const FastOS_Mutex & dsMutex, uint32_t partindex, bool mld)
+FastS_PlainDataSet::getPartitionMLD(const std::unique_lock<std::mutex> &dsGuard, uint32_t partindex, bool mld)
 {
-    (void) dsMutex;
+    (void) dsGuard;
     FastS_EngineBase*  ret = NULL;
     unsigned int oldCount = 1;
     if (partindex < _partMap._num_partitions) {
@@ -429,9 +427,9 @@ FastS_PlainDataSet::getPartitionMLD(const FastOS_Mutex & dsMutex, uint32_t parti
 }
 
 FastS_EngineBase *
-FastS_PlainDataSet::getPartitionMLD(const FastOS_Mutex & dsMutex, uint32_t partindex, bool mld, uint32_t rowid)
+FastS_PlainDataSet::getPartitionMLD(const std::unique_lock<std::mutex> &dsGuard, uint32_t partindex, bool mld, uint32_t rowid)
 {
-    (void) dsMutex;
+    (void) dsGuard;
     FastS_EngineBase*  ret = NULL;
     unsigned int oldCount = 1;
 
@@ -464,11 +462,12 @@ FastS_PlainDataSet::getPartEngines(uint32_t partition)
     typedef FastS_EngineBase EB;
     typedef std::vector<EB *> EBV;
     EBV partEngines;
-    LockDataset();
-    for (FastS_EngineBase *iter = _partMap._partitions[partition]._engines; iter != NULL; iter = iter->_nextpart) {
-        partEngines.push_back(iter);
+    {
+        auto dsGuard(getDsGuard());
+        for (FastS_EngineBase *iter = _partMap._partitions[partition]._engines; iter != NULL; iter = iter->_nextpart) {
+            partEngines.push_back(iter);
+        }
     }
-    UnlockDataset();
     return partEngines;
 }
 
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.h b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.h
index 827abc13ce7..7c04834bd38 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.h
@@ -174,13 +174,13 @@ public:
     PossCount getActiveDocs() const { return _stateOfRows.getActiveDocs(); }
     uint32_t getRandomWeightedRow() const;
 
-    FastS_EngineBase * getPartition(const FastOS_Mutex & lock, uint32_t partid);
-    FastS_EngineBase * getPartition(const FastOS_Mutex & lock, uint32_t partid, uint32_t rowid);
+    FastS_EngineBase * getPartition(const std::unique_lock<std::mutex> &dsGuard, uint32_t partid);
+    FastS_EngineBase * getPartition(const std::unique_lock<std::mutex> &dsGuard, uint32_t partid, uint32_t rowid);
 
     size_t countNodesUpInRow_HasLock(uint32_t rowid);
 
-    FastS_EngineBase * getPartitionMLD(const FastOS_Mutex & lock, uint32_t partid, bool mld);
-    FastS_EngineBase * getPartitionMLD(const FastOS_Mutex & lock, uint32_t partid, bool mld, uint32_t rowid);
+    FastS_EngineBase * getPartitionMLD(const std::unique_lock<std::mutex> &dsGuard, uint32_t partid, bool mld);
+    FastS_EngineBase * getPartitionMLD(const std::unique_lock<std::mutex> &dsGuard, uint32_t partid, bool mld, uint32_t rowid);
 
     std::vector<FastS_EngineBase *> getPartEngines(uint32_t partition);