Increase the life-cycle of threads in thread-pool...

to ScDocument lifetime if possible. This helps to avoid lots
of thread setup-cost while doing recalcs especially if there are
many formula-groups in the document and most of them are fairly
light-weight.

Change-Id: Idd57e1ebd0d4e492f99e31237d4a55ec9c95a121
Reviewed-on: https://gerrit.libreoffice.org/69473
Tested-by: Jenkins
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>

comphelper/source/misc/threadpool.cxx

@@ -213,7 +213,7 @@ std::unique_ptr<ThreadTask> ThreadPool::popWorkLocked( std::unique_lock< std::mu
     return nullptr;
 }
 
-void ThreadPool::waitUntilDone(const std::shared_ptr<ThreadTaskTag>& rTag)
+void ThreadPool::waitUntilDone(const std::shared_ptr<ThreadTaskTag>& rTag, bool bJoinAll)
 {
 #if defined DBG_UTIL && (defined LINUX || defined _WIN32)
     assert(!gbIsWorkerThread && "cannot wait for tasks from inside a task");
@@ -232,12 +232,16 @@ void ThreadPool::waitUntilDone(const std::shared_ptr<ThreadTaskTag>& rTag)
 
     rTag->waitUntilDone();
 
+    if (bJoinAll)
+        joinAll();
+}
+
+void ThreadPool::joinAll()
+{
+    std::unique_lock< std::mutex > aGuard( maMutex );
+    if (maTasks.empty()) // check if there are still tasks from another tag
     {
-        std::unique_lock< std::mutex > aGuard( maMutex );
-        if (maTasks.empty()) // check if there are still tasks from another tag
-        {
-            shutdownLocked(aGuard);
-        }
+        shutdownLocked(aGuard);
     }
 }
 

include/comphelper/threadpool.hxx

@@ -63,8 +63,13 @@ public:
     /// push a new task onto the work queue
     void        pushTask( std::unique_ptr<ThreadTask> pTask);
 
-    /// wait until all queued tasks associated with the tag are completed
-    void        waitUntilDone(const std::shared_ptr<ThreadTaskTag>&);
+    /** Wait until all queued tasks associated with the tag are completed
+        @param  bJoinAll - if set it joins all threads at the end if no other tasks from other tags.
+    */
+    void        waitUntilDone(const std::shared_ptr<ThreadTaskTag>&, bool bJoinAll = true);
+
+    /// join all threads if there are no tasks presently.
+    void        joinAll();
 
     /// return the number of live worker threads
     sal_Int32   getWorkerCount() const { return mnWorkers; }

sc/source/core/data/documen2.cxx

@@ -32,6 +32,7 @@
 #include <tools/urlobj.hxx>
 #include <rtl/crc.h>
 #include <basic/basmgr.hxx>
+#include <comphelper/threadpool.hxx>
 #include <sal/log.hxx>
 
 #include <document.hxx>
@@ -307,6 +308,9 @@ ScDocument::~ScDocument()
 {
     OSL_PRECOND( !bInLinkUpdate, "bInLinkUpdate in dtor" );
 
+    // Join any pending(recalc) threads in global threadpool
+    comphelper::ThreadPool::getSharedOptimalPool().joinAll();
+
     bInDtorClear = true;
 
     // first of all disable all refresh timers by deleting the control

sc/source/core/data/formulacell.cxx

@@ -4758,8 +4758,10 @@ bool ScFormulaCell::InterpretFormulaGroupThreading(sc::FormulaLogger::GroupScope
                                                                 nStartOffset, nEndOffset));
             }
 
-            SAL_INFO("sc.threaded", "Joining threads");
-            rThreadPool.waitUntilDone(aTag);
+            SAL_INFO("sc.threaded", "Waiting for threads to finish work");
+            // Do not join the threads here. They will get joined in ScDocument destructor
+            // if they don't get joined from elsewhere before (via ThreadPool::waitUntilDone).
+            rThreadPool.waitUntilDone(aTag, false);
 
             pDocument->SetThreadedGroupCalcInProgress(false);