[Qt] update block tip (height and date) without locking cs_main, update always (each block)

Author: jonasschnelli

src/qt/clientmodel.cpp

@@ -23,16 +23,13 @@
 #include <QTimer>
 
 static const int64_t nClientStartupTime = GetTime();
+static int64_t nLastBlockTipUpdateNotification = 0;
 
 ClientModel::ClientModel(OptionsModel *optionsModel, QObject *parent) :
     QObject(parent),
     optionsModel(optionsModel),
     peerTableModel(0),
     banTableModel(0),
-    cachedNumBlocks(0),
-    cachedBlockDate(QDateTime()),
-    cachedReindexing(0),
-    cachedImporting(0),
     pollTimer(0)
 {
     peerTableModel = new PeerTableModel(this);
@@ -107,32 +104,8 @@ double ClientModel::getVerificationProgress() const
 
 void ClientModel::updateTimer()
 {
-    // Get required lock upfront. This avoids the GUI from getting stuck on
-    // periodical polls if the core is holding the locks for a longer time -
-    // for example, during a wallet rescan.
-    TRY_LOCK(cs_main, lockMain);
-    if (!lockMain)
-        return;
-
-    // Some quantities (such as number of blocks) change so fast that we don't want to be notified for each change.
-    // Periodically check and update with a timer.
-    int newNumBlocks = getNumBlocks();
-    QDateTime newBlockDate = getLastBlockDate();
-
-    // check for changed number of blocks we have, number of blocks peers claim to have, reindexing state and importing state
-    if (cachedNumBlocks != newNumBlocks ||
-        cachedBlockDate != newBlockDate ||
-        cachedReindexing != fReindex ||
-        cachedImporting != fImporting)
-    {
-        cachedNumBlocks = newNumBlocks;
-        cachedBlockDate = newBlockDate;
-        cachedReindexing = fReindex;
-        cachedImporting = fImporting;
-
-        Q_EMIT numBlocksChanged(newNumBlocks, newBlockDate);
-    }
-
+    // no locking required at this point
+    // the following calls will aquire the required lock
     Q_EMIT mempoolSizeChanged(getMempoolSize(), getMempoolDynamicUsage());
     Q_EMIT bytesChanged(getTotalBytesRecv(), getTotalBytesSent());
 }
@@ -261,13 +234,32 @@ static void BannedListChanged(ClientModel *clientmodel)
     QMetaObject::invokeMethod(clientmodel, "updateBanlist", Qt::QueuedConnection);
 }
 
+static void BlockTipChanged(ClientModel *clientmodel, bool initialSync, const CBlockIndex *pIndex)
+{
+    // lock free async UI updates in case we have a new block tip
+    // during initial sync, only update the UI if the last update
+    // was > 250ms (MODEL_UPDATE_DELAY) ago
+    int64_t now = 0;
+    if (initialSync)
+        now = GetTimeMillis();
+
+    // if we are in-sync, update the UI regardless of last update time
+    if (!initialSync || now - nLastBlockTipUpdateNotification > MODEL_UPDATE_DELAY) {
+        //pass a async signal to the UI thread
+        Q_EMIT clientmodel->numBlocksChanged(pIndex->nHeight, QDateTime::fromTime_t(pIndex->GetBlockTime()));
+        nLastBlockTipUpdateNotification = now;
+    }
+
+}
+
 void ClientModel::subscribeToCoreSignals()
 {
     // Connect signals to client
     uiInterface.ShowProgress.connect(boost::bind(ShowProgress, this, _1, _2));
     uiInterface.NotifyNumConnectionsChanged.connect(boost::bind(NotifyNumConnectionsChanged, this, _1));
     uiInterface.NotifyAlertChanged.connect(boost::bind(NotifyAlertChanged, this, _1, _2));
     uiInterface.BannedListChanged.connect(boost::bind(BannedListChanged, this));
+    uiInterface.NotifyBlockTip.connect(boost::bind(BlockTipChanged, this, _1, _2));
 }
 
 void ClientModel::unsubscribeFromCoreSignals()
@@ -277,4 +269,5 @@ void ClientModel::unsubscribeFromCoreSignals()
     uiInterface.NotifyNumConnectionsChanged.disconnect(boost::bind(NotifyNumConnectionsChanged, this, _1));
     uiInterface.NotifyAlertChanged.disconnect(boost::bind(NotifyAlertChanged, this, _1, _2));
     uiInterface.BannedListChanged.disconnect(boost::bind(BannedListChanged, this));
+    uiInterface.NotifyBlockTip.disconnect(boost::bind(BlockTipChanged, this, _1, _2));
 }

src/qt/clientmodel.h

@@ -81,11 +81,6 @@ class ClientModel : public QObject
     PeerTableModel *peerTableModel;
     BanTableModel *banTableModel;
 
-    int cachedNumBlocks;
-    QDateTime cachedBlockDate;
-    bool cachedReindexing;
-    bool cachedImporting;
-
     QTimer *pollTimer;
 
     void subscribeToCoreSignals();