diff --git a/dsl.cc b/dsl.cc
index 164a42fe4..b7ffbf34f 100644
--- a/dsl.cc
+++ b/dsl.cc
@@ -56,6 +56,8 @@
 // For SVG handling
 #include <QtSvg/QSvgRenderer>
 
+#include <QtConcurrent>
+
 #include "utils.hh"
 
 namespace Dsl {
@@ -1561,6 +1563,7 @@ class DslArticleRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -1569,7 +1572,8 @@ class DslArticleRequest: public Dictionary::DataRequest
                      DslDictionary & dict_, bool ignoreDiacritics_ ):
     word( word_ ), alts( alts_ ), dict( dict_ ), ignoreDiacritics( ignoreDiacritics_ )
   {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
   }
 
   void run();
@@ -1582,6 +1586,7 @@ class DslArticleRequest: public Dictionary::DataRequest
   ~DslArticleRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     //hasExited.acquire();
   }
 };
@@ -1733,6 +1738,7 @@ class DslResourceRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -1741,7 +1747,8 @@ class DslResourceRequest: public Dictionary::DataRequest
     dict( dict_ ),
     resourceName( resourceName_ )
   {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
   }
 
   void run();
@@ -1754,6 +1761,7 @@ class DslResourceRequest: public Dictionary::DataRequest
   ~DslResourceRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     //hasExited.acquire();
   }
 };
diff --git a/epwing.cc b/epwing.cc
index 2f9ef6077..bdb1d28be 100644
--- a/epwing.cc
+++ b/epwing.cc
@@ -10,6 +10,7 @@
 #include <QSemaphore>
 
 #include <map>
+#include <QtConcurrent>
 #include <set>
 #include <string>
 
@@ -461,6 +462,7 @@ class EpwingArticleRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -469,8 +471,9 @@ class EpwingArticleRequest: public Dictionary::DataRequest
                         EpwingDictionary & dict_, bool ignoreDiacritics_ ):
     word( word_ ), alts( alts_ ), dict( dict_ ), ignoreDiacritics( ignoreDiacritics_ )
   {
-    QThreadPool::globalInstance()->start(
-      new EpwingArticleRequestRunnable( *this, hasExited ) );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start(
+    //   new EpwingArticleRequestRunnable( *this, hasExited ) );
   }
 
   void run(); // Run from another thread by EpwingArticleRequestRunnable
@@ -483,7 +486,8 @@ class EpwingArticleRequest: public Dictionary::DataRequest
   ~EpwingArticleRequest()
   {
     isCancelled.ref();
-    hasExited.acquire();
+    f.waitForFinished();
+    // hasExited.acquire();
   }
 };
 
diff --git a/ftshelpers.cc b/ftshelpers.cc
index 29bf509ac..680ace671 100644
--- a/ftshelpers.cc
+++ b/ftshelpers.cc
@@ -443,27 +443,19 @@ void FTSResultsRequest::checkArticles( QVector< uint32_t > const & offsets,
                                        QStringList const & words,
                                        QRegExp const & searchRegexp )
 {
-  const int parallel_count = QThread::idealThreadCount()/2;
-  QSemaphore sem( parallel_count  < 1 ? 1 : parallel_count  );
-
-  QFutureSynchronizer< void > synchronizer;
+  // const int parallel_count = QThread::idealThreadCount()/2;
+  // QSemaphore sem( parallel_count  < 1 ? 1 : parallel_count  );
+  //
+  // QFutureSynchronizer< void > synchronizer;
   const auto searchRegularExpression = createMatchRegex( searchRegexp );
 
   for( auto & address : offsets )
   {
     if( Utils::AtomicInt::loadAcquire( isCancelled ) )
     {
-      synchronizer.setCancelOnWait(true);
       return;
     }
-    sem.acquire();
-    QFuture< void > f = QtConcurrent::run(
-      [ =,&sem ]()
-      {
-        QSemaphoreReleaser releaser( sem );
-        checkSingleArticle( address, words,  searchRegularExpression );
-      } );
-    synchronizer.addFuture( f );
+    checkSingleArticle( address, words, searchRegularExpression );
   }
 }
 
@@ -723,7 +715,18 @@ void FTSResultsRequest::indexSearch( BtreeIndexing::BtreeIndex & ftsIndex,
     }
   };
   // int n = indexWords.length();
-  QtConcurrent::blockingMap( indexWords, findLinks );
+  // QtConcurrent::blockingMap( indexWords, findLinks );
+
+  for(QString word:indexWords)
+  {
+    if( Utils::AtomicInt::loadAcquire( isCancelled ) )
+    {
+      return;
+    }
+    findLinks( word );
+  }
+
+  // blocked execution.
 
   int i = 0;
   for( auto & elem : addressLists )
@@ -807,6 +810,7 @@ void FTSResultsRequest::combinedIndexSearch( BtreeIndexing::BtreeIndex & ftsInde
       {
         if( Utils::AtomicInt::loadAcquire( isCancelled ) )
         {
+          Mutex::Lock _( dataMutex );
           sets << tmp;
           return;
         }
@@ -839,7 +843,20 @@ void FTSResultsRequest::combinedIndexSearch( BtreeIndexing::BtreeIndex & ftsInde
         sets << tmp;
       }
     };
-    QtConcurrent::blockingMap( wordsList, fn_wordLink );
+    // QtConcurrent::blockingMap( wordsList, fn_wordLink );
+
+    {
+
+      for(const auto & word : wordsList )
+      {
+        if( Utils::AtomicInt::loadAcquire( isCancelled ) )
+        {
+          return;
+        }
+        fn_wordLink( word );
+      }
+    }
+    //blocked execution.
 
     int i = 0;
     for( auto & elem : sets )
diff --git a/ftshelpers.hh b/ftshelpers.hh
index 5a5ac6ea0..cf02a06c0 100644
--- a/ftshelpers.hh
+++ b/ftshelpers.hh
@@ -10,6 +10,7 @@
 #include <QRunnable>
 #include <QSemaphore>
 #include <QList>
+#include <QtConcurrent>
 
 #include "dictionary.hh"
 #include "btreeidx.hh"
@@ -83,6 +84,7 @@ class FTSResultsRequest : public Dictionary::DataRequest
   QAtomicInt isCancelled;
 
   QAtomicInt results;
+  QFuture< void > f;
 
   QList< FTS::FtsHeadword > * foundHeadwords;
 
@@ -135,7 +137,8 @@ public:
 
     foundHeadwords = new QList< FTS::FtsHeadword >;
     results         = 0;
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); }, -100 );
+    f              = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); }, -100 );
   }
 
   void run();
@@ -148,6 +151,7 @@ public:
   ~FTSResultsRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     if( foundHeadwords )
       delete foundHeadwords;
   }
diff --git a/mdx.cc b/mdx.cc
index b096959c0..fb1df58fd 100644
--- a/mdx.cc
+++ b/mdx.cc
@@ -43,6 +43,7 @@
 #include "tiff.hh"
 #include "utils.hh"
 #include "base/globalregex.hh"
+#include <QtConcurrent>
 
 namespace Mdx
 {
@@ -173,17 +174,23 @@ class IndexedMdd: public BtreeIndexing::BtreeIndex
       return false;
     }
 
-    ScopedMemMap compressed( mddFile, indexEntry.compressedBlockPos, indexEntry.compressedBlockSize );
-    if ( !compressed.startAddress() )
-    {
-      return false;
-    }
-
     QByteArray decompressed;
-    if ( !MdictParser::parseCompressedBlock( indexEntry.compressedBlockSize, ( char * )compressed.startAddress(),
-                                             indexEntry.decompressedBlockSize, decompressed ) )
+
     {
-      return false;
+      Mutex::Lock _( idxMutex );
+      ScopedMemMap compressed( mddFile, indexEntry.compressedBlockPos, indexEntry.compressedBlockSize );
+      if( !compressed.startAddress() )
+      {
+        return false;
+      }
+
+      if( !MdictParser::parseCompressedBlock( indexEntry.compressedBlockSize,
+                                              (char *)compressed.startAddress(),
+                                              indexEntry.decompressedBlockSize,
+                                              decompressed ) )
+      {
+        return false;
+      }
     }
 
     result.resize( indexEntry.recordSize );
@@ -527,6 +534,7 @@ class MdxArticleRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -539,7 +547,8 @@ class MdxArticleRequest: public Dictionary::DataRequest
     dict( dict_ ),
     ignoreDiacritics( ignoreDiacritics_ )
   {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start(  );
   }
 
   void run();
@@ -552,7 +561,8 @@ class MdxArticleRequest: public Dictionary::DataRequest
   ~MdxArticleRequest()
   {
     isCancelled.ref();
-    //hasExited.acquire();
+    f.waitForFinished();
+    // hasExited.acquire();
   }
 };
 
@@ -681,6 +691,7 @@ class MddResourceRequest: public Dictionary::DataRequest
   wstring resourceName;
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -689,7 +700,8 @@ class MddResourceRequest: public Dictionary::DataRequest
     dict( dict_ ),
     resourceName( Utf8::decode( resourceName_ ) )
   {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
   }
 
   void run();
@@ -702,6 +714,7 @@ class MddResourceRequest: public Dictionary::DataRequest
   ~MddResourceRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     //hasExited.acquire();
   }
 };
diff --git a/zim.cc b/zim.cc
index 6dc8a9b14..de827bfcf 100644
--- a/zim.cc
+++ b/zim.cc
@@ -41,6 +41,7 @@
 #include <set>
 #include <map>
 #include <algorithm>
+#include <QtConcurrent>
 
 namespace Zim {
 
@@ -1248,6 +1249,7 @@ class ZimArticleRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
 
@@ -1256,7 +1258,8 @@ class ZimArticleRequest: public Dictionary::DataRequest
                      ZimDictionary & dict_, bool ignoreDiacritics_ ):
     word( word_ ), alts( alts_ ), dict( dict_ ), ignoreDiacritics( ignoreDiacritics_ )
   {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
   }
 
   void run();
@@ -1269,6 +1272,7 @@ class ZimArticleRequest: public Dictionary::DataRequest
   ~ZimArticleRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     //hasExited.acquire();
   }
 };
@@ -1421,11 +1425,13 @@ class ZimResourceRequest: public Dictionary::DataRequest
 
   QAtomicInt isCancelled;
   QSemaphore hasExited;
+  QFuture< void > f;
 
 public:
   ZimResourceRequest(ZimDictionary &dict_, string const &resourceName_)
       : dict(dict_), resourceName(resourceName_) {
-    QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
+    f = QtConcurrent::run( [ this ]() { this->run(); } );
+    // QThreadPool::globalInstance()->start( [ this ]() { this->run(); } );
   }
 
   void run();
@@ -1438,6 +1444,7 @@ class ZimResourceRequest: public Dictionary::DataRequest
   ~ZimResourceRequest()
   {
     isCancelled.ref();
+    f.waitForFinished();
     //hasExited.acquire();
   }
 };