Fix mutex locking

Author: wks

openjdk/share/mmtkHeap.cpp

@@ -77,7 +77,7 @@ MMTkHeap* MMTkHeap::_heap = NULL;
 MMTkHeap::MMTkHeap() :
   CollectedHeap(),
   _n_workers(0),
-  _gc_lock(new Monitor(Mutex::safepoint, "MMTkHeap::_gc_lock", true)),
+  _gc_lock(new Monitor(Mutex::nosafepoint, "MMTkHeap::_gc_lock", true)),
   _num_root_scan_tasks(0),
   _soft_ref_policy(),
   _last_gc_time(0)

openjdk/share/mmtkUpcalls.cpp

@@ -94,6 +94,15 @@ static void mmtk_resume_mutators(void *tls) {
     MutexLocker locker(MMTkHeap::heap()->gc_lock(), Mutex::_no_safepoint_check_flag);
     MMTkHeap::heap()->gc_lock()->notify_all();
   }
+
+  log_debug(gc)("Notifying mutators blocking on Heap_lock for reference pending list...");
+  // Note: That's the ReferenceHandler thread.
+  {
+    MutexLocker x(Heap_lock, Mutex::_no_safepoint_check_flag);
+    if (Universe::has_reference_pending_list()) {
+      Heap_lock->notify_all();
+    }
+  }
 }
 
 static const int GC_THREAD_KIND_WORKER = 1;

openjdk/share/mmtkVMCompanionThread.cpp

@@ -163,11 +163,4 @@ void MMTkVMCompanionThread::do_mmtk_stw_operation() {
     log_trace(gc)("do_mmtk_stw_operation: Reached _thread_resumed state. Notifying...");
     _lock->notify_all();
   }
-
-  {
-    MutexLocker x(Heap_lock, Mutex::_no_safepoint_check_flag);
-    if (Universe::has_reference_pending_list()) {
-      Heap_lock->notify_all();
-    }
-  }
 }