8149789: SIGSEGV in CompileTask::print

Print tasks from active compile threads requires safepoint

Reviewed-by: kvn

hotspot/src/share/vm/compiler/compileBroker.cpp

@@ -469,7 +469,6 @@ CompileQueue* CompileBroker::compile_queue(int comp_level) {
 void CompileBroker::print_compile_queues(outputStream* st) {
   st->print_cr("Current compiles: ");
   MutexLocker locker(MethodCompileQueue_lock);
-  MutexLocker locker2(Threads_lock);
 
   char buf[2000];
   int buflen = sizeof(buf);

hotspot/src/share/vm/runtime/vm_operations.cpp

@@ -485,6 +485,10 @@ void VM_Exit::wait_if_vm_exited() {
   }
 }
 
+void VM_PrintCompileQueue::doit() {
+  CompileBroker::print_compile_queues(_out);
+}
+
 #if INCLUDE_SERVICES
 void VM_PrintClassHierarchy::doit() {
   KlassHierarchy::print_class_hierarchy(_out, _print_interfaces, _print_subclasses, _classname);

hotspot/src/share/vm/runtime/vm_operations.hpp

@@ -105,6 +105,7 @@
   template(DumpHashtable)                         \
   template(DumpTouchedMethods)                    \
   template(MarkActiveNMethods)                    \
+  template(PrintCompileQueue)                     \
   template(PrintClassHierarchy)                   \
 
 class VM_Operation: public CHeapObj<mtInternal> {
@@ -421,6 +422,17 @@ class VM_Exit: public VM_Operation {
   void doit();
 };
 
+class VM_PrintCompileQueue: public VM_Operation {
+ private:
+  outputStream* _out;
+
+ public:
+  VM_PrintCompileQueue(outputStream* st) : _out(st) {}
+  VMOp_Type type() const { return VMOp_PrintCompileQueue; }
+  Mode evaluation_mode() const { return _safepoint; }
+  void doit();
+};
+
 #if INCLUDE_SERVICES
 class VM_PrintClassHierarchy: public VM_Operation {
  private:

hotspot/src/share/vm/services/diagnosticCommand.cpp

@@ -832,7 +832,8 @@ void VMDynamicLibrariesDCmd::execute(DCmdSource source, TRAPS) {
 }
 
 void CompileQueueDCmd::execute(DCmdSource source, TRAPS) {
-  CompileBroker::print_compile_queues(output());
+  VM_PrintCompileQueue printCompileQueueOp(output());
+  VMThread::execute(&printCompileQueueOp);
 }
 
 void CodeListDCmd::execute(DCmdSource source, TRAPS) {