rhbz#1036877: Join Java AsynchronousFinalizer thread well before exit

AsynchronousFinalizer was originally added as
870a4401c05beec3d31c1f6055a64591edd0a9d9 "INTEGRATION: CWS mtg1: #i57753# Avoid
long-running finalize methods" referring to
<https://issues.apache.org/ooo/show_bug.cgi?id=57753> " Fix JNI-UNO bridge so
that the JVM doesn't run out of memory when a destructor locks the SolarMutex."

It is unclear to me how relevant "If JVMs are getting more mature and should no
longer have problems with long-running finalize methods, this class could be
removed again" really is in practice.  After all, advice on hotspot-gc-devel is
to avoid finalize() if possible
(<http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2014-June/010215.html>
"Re: History of finalizer execution and gc progress?").  So stick with this
approach of home-grown draining for now (where a home-grown approach using
PhantomReferencens would need a dedicated draining thread, too, so would not
have much benefit over the existing code in practice).

Timely termination of AsynchronousFinalizer threads is achieved by using a
dedicated thread per bridge and joining it in the remote bridge's dispose()
resp. the JNI environment's new java_env_dispose.

Change-Id: Idcef2dbf361a1de22f60db73828f59e85711aea7

1 files changed, 16 insertions, 0 deletions

diff --git a/cppuhelper/source/component_context.cxx b/cppuhelper/source/component_context.cxx
index 16642e9133fb..53b5eb000468 100644
--- a/cppuhelper/source/component_context.cxx
+++ b/cppuhelper/source/component_context.cxx
@@ -731,6 +731,22 @@ void ComponentContext::disposing()
     for ( ; iPos != iEnd; ++iPos )
         delete iPos->second;
     m_map.clear();
+
+    // Hack to terminate any JNI bridge's AsynchronousFinalizer thread (as JNI
+    // proxies get finalized with arbitrary delay, so the bridge typically does
+    // not dispose itself early enough before the process exits):
+    uno_Environment ** envs;
+    sal_Int32 envCount;
+    uno_getRegisteredEnvironments(
+        &envs, &envCount, &rtl_allocateMemory, OUString("java").pData);
+    assert(envCount >= 0);
+    assert(envCount == 0 || envs != nullptr);
+    for (sal_Int32 i = 0; i != envCount; ++i) {
+        assert(envs[i] != nullptr);
+        assert(envs[i]->dispose != nullptr);
+        (*envs[i]->dispose)(envs[i]);
+    }
+    rtl_freeMemory(envs);
 }
 
 ComponentContext::ComponentContext(