comphelper,vcl: let DeInitVCL() join some AsyncEventNotifier threads

comphelper::AsyncEventNotifier is an amazing class that dispatches
events in separate threads, no doubt implemented during times of
exuberant optimism about the tractability of shared-state
multi-threading.

Unfortunately the authors forgot to think about how all those awesome
threads will be joined, so if they are somehow blocked, then it may well
happen that the events are dispatched when the main thread is already in
DeInitVCL, and the objects required for the dispatching already smell
somewhat funny.

This happens quite reproducibly when changing dbaccess' ModelMethodGuard
to lock the SolarMutex too, then CppunitTest_dbaccess_RowSetClones
crashes in DeInitVCL() because one AsyncEventNotifier thread was blocked
until then by SolarMutexGuard, and this test never Yields once its
document is loaded.

Try to fix this by joining the "DocumentEventNotifier" threads from
DeInitVCL() itself.

Since there's no rtl::WeakReference to go with rtl::Reference, refactor
the AsyncEventNotifier and create a new AsyncEventNotifierAutoJoin
that has to be used with std::shared_ptr and std::weak_ptr.

Change-Id: I50a0749795acb04b0776e543f7125767b697ea35
Reviewed-on: https://gerrit.libreoffice.org/27581
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>

1 files changed, 121 insertions, 7 deletions

diff --git a/comphelper/source/misc/asyncnotification.cxx b/comphelper/source/misc/asyncnotification.cxx
index 85643e2b3cf4..e13be286a5dd 100644
--- a/comphelper/source/misc/asyncnotification.cxx
+++ b/comphelper/source/misc/asyncnotification.cxx
@@ -21,10 +21,12 @@
 #include <osl/diagnose.h>
 #include <osl/mutex.hxx>
 #include <osl/conditn.hxx>
+#include <rtl/instance.hxx>
 #include <comphelper/guarding.hxx>
 
 #include <cassert>
 #include <deque>
+#include <vector>
 #include <functional>
 #include <algorithm>
 
@@ -76,6 +78,9 @@ namespace comphelper
         ::osl::Condition    aPendingActions;
         EventQueue          aEvents;
         bool                bTerminate;
+        // only used for AsyncEventNotifierAutoJoin
+        char const*         name;
+        std::shared_ptr<AsyncEventNotifierAutoJoin> pKeepThisAlive;
 
         EventNotifierImpl()
             :bTerminate( false )
@@ -83,18 +88,18 @@ namespace comphelper
         }
     };
 
-    AsyncEventNotifier::AsyncEventNotifier(char const * name):
-        Thread(name), m_xImpl(new EventNotifierImpl)
+    AsyncEventNotifierBase::AsyncEventNotifierBase()
+        : m_xImpl(new EventNotifierImpl)
     {
     }
 
 
-    AsyncEventNotifier::~AsyncEventNotifier()
+    AsyncEventNotifierBase::~AsyncEventNotifierBase()
     {
     }
 
 
-    void AsyncEventNotifier::removeEventsForProcessor( const ::rtl::Reference< IEventProcessor >& _xProcessor )
+    void AsyncEventNotifierBase::removeEventsForProcessor( const ::rtl::Reference< IEventProcessor >& _xProcessor )
     {
         ::osl::MutexGuard aGuard( m_xImpl->aMutex );
 
@@ -103,7 +108,7 @@ namespace comphelper
     }
 
 
-    void SAL_CALL AsyncEventNotifier::terminate()
+    void SAL_CALL AsyncEventNotifierBase::terminate()
     {
         ::osl::MutexGuard aGuard( m_xImpl->aMutex );
 
@@ -115,7 +120,7 @@ namespace comphelper
     }
 
 
-    void AsyncEventNotifier::addEvent( const AnyEventRef& _rEvent, const ::rtl::Reference< IEventProcessor >& _xProcessor )
+    void AsyncEventNotifierBase::addEvent( const AnyEventRef& _rEvent, const ::rtl::Reference< IEventProcessor >& _xProcessor )
     {
         ::osl::MutexGuard aGuard( m_xImpl->aMutex );
 
@@ -128,7 +133,7 @@ namespace comphelper
     }
 
 
-    void AsyncEventNotifier::execute()
+    void AsyncEventNotifierBase::execute()
     {
         for (;;)
         {
@@ -160,6 +165,115 @@ namespace comphelper
         }
     }
 
+    AsyncEventNotifier::AsyncEventNotifier(char const* name)
+        : salhelper::Thread(name)
+    {
+    }
+
+    AsyncEventNotifier::~AsyncEventNotifier()
+    {
+    }
+
+    void AsyncEventNotifier::execute()
+    {
+        return AsyncEventNotifierBase::execute();
+    }
+
+    void AsyncEventNotifier::terminate()
+    {
+        return AsyncEventNotifierBase::terminate();
+    }
+
+    struct theNotifiersMutex : public rtl::Static<osl::Mutex, theNotifiersMutex> {};
+    static std::vector<std::weak_ptr<AsyncEventNotifierAutoJoin>> g_Notifiers;
+
+    void JoinAsyncEventNotifiers()
+    {
+        std::vector<std::weak_ptr<AsyncEventNotifierAutoJoin>> notifiers;
+        {
+            ::osl::MutexGuard g(theNotifiersMutex::get());
+            notifiers = g_Notifiers;
+        }
+        for (std::weak_ptr<AsyncEventNotifierAutoJoin> const& wNotifier : notifiers)
+        {
+            std::shared_ptr<AsyncEventNotifierAutoJoin> const pNotifier(
+                    wNotifier.lock());
+            if (pNotifier)
+            {
+                pNotifier->terminate();
+                pNotifier->join();
+            }
+        }
+        // note it's possible that g_Notifiers isn't empty now in case of leaks,
+        // particularly since the UNO service manager isn't disposed yet
+    }
+
+    AsyncEventNotifierAutoJoin::AsyncEventNotifierAutoJoin(char const* name)
+    {
+        m_xImpl->name = name;
+    }
+
+    AsyncEventNotifierAutoJoin::~AsyncEventNotifierAutoJoin()
+    {
+        ::osl::MutexGuard g(theNotifiersMutex::get());
+        // note: this doesn't happen atomically with the refcount
+        // hence it's possible this deletes > 1 or 0 elements
+        g_Notifiers.erase(
+            std::remove_if(g_Notifiers.begin(), g_Notifiers.end(),
+                [](std::weak_ptr<AsyncEventNotifierAutoJoin> const& w) {
+                    return w.expired();
+                } ),
+            g_Notifiers.end());
+    }
+
+    std::shared_ptr<AsyncEventNotifierAutoJoin>
+    AsyncEventNotifierAutoJoin::newAsyncEventNotifierAutoJoin(char const* name)
+    {
+        std::shared_ptr<AsyncEventNotifierAutoJoin> const ret(
+                new AsyncEventNotifierAutoJoin(name));
+        ::osl::MutexGuard g(theNotifiersMutex::get());
+        g_Notifiers.push_back(ret);
+        return ret;
+    }
+
+    void AsyncEventNotifierAutoJoin::terminate()
+    {
+        return AsyncEventNotifierBase::terminate();
+    }
+
+    void AsyncEventNotifierAutoJoin::launch(std::shared_ptr<AsyncEventNotifierAutoJoin> const& xThis)
+    {
+        // see salhelper::Thread::launch
+        xThis->m_xImpl->pKeepThisAlive = xThis;
+        try {
+            if (!xThis->create()) {
+                throw std::runtime_error("osl::Thread::create failed");
+            }
+        } catch (...) {
+            xThis->m_xImpl->pKeepThisAlive.reset();
+            throw;
+        }
+    }
+
+    void AsyncEventNotifierAutoJoin::run()
+    {
+        // see salhelper::Thread::run
+        try {
+            setName(m_xImpl->name);
+            execute();
+        } catch (...) {
+            onTerminated();
+            throw;
+        }
+    }
+
+    void AsyncEventNotifierAutoJoin::onTerminated()
+    {
+        // try to delete "this"
+        m_xImpl->pKeepThisAlive.reset();
+        return osl::Thread::onTerminated();
+    }
+
 } // namespace comphelper