Allow the comphelper threadpool to be reset after construction.

Otherwise some pre-init components can start it, and threads get
stranded in the forkit process causing grief.

Change-Id: I104a38271662e9f8cc2fd128e7b758700fd3ca84
Reviewed-on: https://gerrit.libreoffice.org/52859Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>

comphelper/source/misc/threadpool.cxx

@@ -134,12 +134,21 @@ ThreadPool::ThreadPool( sal_Int32 nWorkers ) :
     mnThreadsWorking( 0 ),
     mbTerminate( false )
 {
+    launchWorkers( nWorkers );
+}
+
+void ThreadPool::launchWorkers( sal_Int32 nWorkers )
+{
+    osl::MutexGuard aGuard( maGuard );
+
+    mbTerminate = false;
+    mnThreadsWorking = 0;
+
     for( sal_Int32 i = 0; i < nWorkers; i++ )
         maWorkers.push_back( new ThreadWorker( this ) );
 
     maTasksComplete.set();
 
-    osl::MutexGuard aGuard( maGuard );
     for(rtl::Reference<ThreadWorker> & rpWorker : maWorkers)
         rpWorker->launch();
 }
@@ -160,7 +169,15 @@ struct ThreadPoolStatic : public rtl::StaticWithInit< std::shared_ptr< ThreadPoo
 
 ThreadPool& ThreadPool::getSharedOptimalPool()
 {
-    return *ThreadPoolStatic::get().get();
+    ThreadPool *pPool = ThreadPoolStatic::get().get();
+    if (pPool->maWorkers.size() <= 0)
+        pPool->launchWorkers( ThreadPool::getPreferredConcurrency() );
+    return *pPool;
+}
+
+void ThreadPool::resetSharedOptimalPool()
+{
+    ThreadPoolStatic::get()->waitAndCleanupWorkers();
 }
 
 sal_Int32 ThreadPool::getPreferredConcurrency()

desktop/source/lib/init.cxx

@@ -35,6 +35,7 @@
 #include <comphelper/string.hxx>
 #include <comphelper/propertysequence.hxx>
 #include <comphelper/scopeguard.hxx>
+#include <comphelper/threadpool.hxx>
 
 #include <com/sun/star/beans/XPropertySet.hpp>
 #include <com/sun/star/container/XNameAccess.hpp>
@@ -3816,7 +3817,10 @@ static int lo_initialize(LibreOfficeKit* pThis, const char* pAppPath, const char
     }
 
     if (eStage == PRE_INIT)
+    {
+        comphelper::ThreadPool::resetSharedOptimalPool();
         rtl_alloc_preInit(sal_False);
+    }
 
     return bInitialized;
 }

include/comphelper/threadpool.hxx

@@ -43,6 +43,9 @@ public:
     /// count for the CPU
     static      ThreadPool& getSharedOptimalPool();
 
+    /// resets / closes shared optimal pool workers.
+    static      void resetSharedOptimalPool();
+
     static std::shared_ptr<ThreadTaskTag> createThreadTaskTag();
 
     static bool isTaskTagDone(const std::shared_ptr<ThreadTaskTag>&);
@@ -56,6 +59,9 @@ public:
     ThreadPool( sal_Int32 nWorkers );
     ~ThreadPool();
 
+    /// Instantiate a given number of workers
+    void        launchWorkers( sal_Int32 nWorkers );
+
     /// push a new task onto the work queue
     void        pushTask( ThreadTask *pTask /* takes ownership */ );