8273107: RunThese24H times out with "java.lang.management.ThreadInfo.getLockName()" is null

src/hotspot/share/runtime/monitorDeflationThread.cpp

@@ -63,6 +63,6 @@ void MonitorDeflationThread::monitor_deflation_thread_entry(JavaThread* jt, TRAP
       }
     }
 
-    (void)ObjectSynchronizer::deflate_idle_monitors();
+    (void)ObjectSynchronizer::deflate_idle_monitors(/* ObjectMonitorsHashtable is not needed here */ nullptr);
   }
 }

src/hotspot/share/runtime/synchronizer.cpp

@@ -57,6 +57,40 @@
 #include "utilities/events.hpp"
 #include "utilities/preserveException.hpp"
 
+class CleanupObjectMonitorsHashtable: StackObj {
+ public:
+  bool do_entry(JavaThread*& key, ObjectMonitorsHashtable::PtrList*& list) {
+    list->clear();  // clear the LinkListNodes
+    delete list;    // then delete the LinkedList
+    return true;
+  }
+};
+
+ObjectMonitorsHashtable::~ObjectMonitorsHashtable() {
+  CleanupObjectMonitorsHashtable cleanup;
+  _ptrs->unlink(&cleanup);  // cleanup the LinkedLists
+  delete _ptrs;             // then delete the hash table
+}
+
+void ObjectMonitorsHashtable::add_entry(JavaThread* jt, ObjectMonitor* om) {
+  ObjectMonitorsHashtable::PtrList* list = get_entry(jt);
+  if (list == nullptr) {
+    // Create new list and add it to the hash table:
+    list = new (ResourceObj::C_HEAP, mtThread) ObjectMonitorsHashtable::PtrList();
+    add_entry(jt, list);
+  }
+  list->add(om);  // Add the ObjectMonitor to the list.
+  _om_count++;
+}
+
+bool ObjectMonitorsHashtable::has_entry(JavaThread* jt, ObjectMonitor* om) {
+  ObjectMonitorsHashtable::PtrList* list = get_entry(jt);
+  if (list == nullptr || list->find(om) == nullptr) {
+    return false;
+  }
+  return true;
+}
+
 void MonitorList::add(ObjectMonitor* m) {
   ObjectMonitor* head;
   do {
@@ -992,11 +1026,18 @@ JavaThread* ObjectSynchronizer::get_lock_owner(ThreadsList * t_list, Handle h_ob
 
 // Visitors ...
 
+// Iterate ObjectMonitors where the owner == thread; this does NOT include
+// ObjectMonitors where owner is set to a stack lock address in thread.
+//
+// This version of monitors_iterate() works with the in-use monitor list.
+//
 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure, JavaThread* thread) {
   MonitorList::Iterator iter = _in_use_list.iterator();
   while (iter.has_next()) {
     ObjectMonitor* mid = iter.next();
     if (mid->owner() != thread) {
+      // Not owned by the target thread and intentionally skips when owner
+      // is set to a stack lock address in the target thread.
       continue;
     }
     if (!mid->is_being_async_deflated() && mid->object_peek() != NULL) {
@@ -1013,6 +1054,31 @@ void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure, JavaThread* t
   }
 }
 
+// This version of monitors_iterate() works with the specified linked list.
+//
+void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure,
+                                          ObjectMonitorsHashtable::PtrList* list,
+                                          JavaThread* thread) {
+  typedef LinkedListIterator<ObjectMonitor*> ObjectMonitorIterator;
+  ObjectMonitorIterator iter(list->head());
+  while (!iter.is_empty()) {
+    ObjectMonitor* mid = *iter.next();
+    // Owner set to a stack lock address in thread should never be seen here:
+    assert(mid->owner() == thread, "must be");
+    if (!mid->is_being_async_deflated() && mid->object_peek() != NULL) {
+      // Only process with closure if the object is set.
+
+      // monitors_iterate() is only called at a safepoint or when the
+      // target thread is suspended or when the target thread is
+      // operating on itself. The current closures in use today are
+      // only interested in an owned ObjectMonitor and ownership
+      // cannot be dropped under the calling contexts so the
+      // ObjectMonitor cannot be async deflated.
+      closure->do_monitor(mid);
+    }
+  }
+}
+
 static bool monitors_used_above_threshold(MonitorList* list) {
   if (MonitorUsedDeflationThreshold == 0) {  // disabled case is easy
     return false;
@@ -1338,8 +1404,17 @@ void ObjectSynchronizer::chk_for_block_req(JavaThread* current, const char* op_n
 
 // Walk the in-use list and deflate (at most MonitorDeflationMax) idle
 // ObjectMonitors. Returns the number of deflated ObjectMonitors.
+//
+// If table != nullptr, we gather owned ObjectMonitors indexed by the
+// owner in the table. Please note that ObjectMonitors where the owner
+// is set to a stack lock address are NOT associated with the JavaThread
+// that holds that stack lock. All of the current consumers of
+// ObjectMonitorsHashtable info only care about JNI locked monitors and
+// those do not have the owner set to a stack lock address.
+//
 size_t ObjectSynchronizer::deflate_monitor_list(Thread* current, LogStream* ls,
-                                                elapsedTimer* timer_p) {
+                                                elapsedTimer* timer_p,
+                                                ObjectMonitorsHashtable* table) {
   MonitorList::Iterator iter = _in_use_list.iterator();
   size_t deflated_count = 0;
 
@@ -1350,6 +1425,18 @@ size_t ObjectSynchronizer::deflate_monitor_list(Thread* current, LogStream* ls,
     ObjectMonitor* mid = iter.next();
     if (mid->deflate_monitor()) {
       deflated_count++;
+    } else if (table != nullptr) {
+      // The caller is interested in the owned ObjectMonitors. This does
+      // not include when owner is set to a stack lock address in thread.
+      // This also does not capture unowned ObjectMonitors that cannot be
+      // deflated because of a waiter.
+      JavaThread* jt = (JavaThread*)mid->owner();
+      // Since deflate_idle_monitors() and deflate_monitor_list() can be
+      // called more than once, we have to make sure the entry has not
+      // already been added.
+      if (jt != nullptr && !table->has_entry(jt, mid)) {
+        table->add_entry(jt, mid);
+      }
     }
 
     if (current->is_Java_thread()) {
@@ -1374,8 +1461,8 @@ class HandshakeForDeflation : public HandshakeClosure {
 
 // This function is called by the MonitorDeflationThread to deflate
 // ObjectMonitors. It is also called via do_final_audit_and_print_stats()
-// by the VMThread.
-size_t ObjectSynchronizer::deflate_idle_monitors() {
+// and VM_ThreadDump::doit() by the VMThread.
+size_t ObjectSynchronizer::deflate_idle_monitors(ObjectMonitorsHashtable* table) {
   Thread* current = Thread::current();
   if (current->is_Java_thread()) {
     // The async deflation request has been processed.
@@ -1400,7 +1487,7 @@ size_t ObjectSynchronizer::deflate_idle_monitors() {
   }
 
   // Deflate some idle ObjectMonitors.
-  size_t deflated_count = deflate_monitor_list(current, ls, &timer);
+  size_t deflated_count = deflate_monitor_list(current, ls, &timer, table);
   if (deflated_count > 0 || is_final_audit()) {
     // There are ObjectMonitors that have been deflated or this is the
     // final audit and all the remaining ObjectMonitors have been
@@ -1458,6 +1545,10 @@ size_t ObjectSynchronizer::deflate_idle_monitors() {
     }
     ls->print_cr("end deflating: in_use_list stats: ceiling=" SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT,
                  in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max());
+    if (table != nullptr) {
+      ls->print_cr("ObjectMonitorsHashtable: jt_count=" SIZE_FORMAT ", om_count=" SIZE_FORMAT,
+                   table->jt_count(), table->om_count());
+    }
   }
 
   OM_PERFDATA_OP(MonExtant, set_value(_in_use_list.count()));
@@ -1560,7 +1651,7 @@ void ObjectSynchronizer::do_final_audit_and_print_stats() {
     // Do a deflation in order to reduce the in-use monitor population
     // that is reported by ObjectSynchronizer::log_in_use_monitor_details()
     // which is called by ObjectSynchronizer::audit_and_print_stats().
-    while (ObjectSynchronizer::deflate_idle_monitors() != 0) {
+    while (ObjectSynchronizer::deflate_idle_monitors(/* ObjectMonitorsHashtable is not needed here */ nullptr) >= (size_t)MonitorDeflationMax) {
       ; // empty
     }
     // The other audit_and_print_stats() call is done at the Debug

src/hotspot/share/runtime/synchronizer.hpp

@@ -30,11 +30,68 @@
 #include "runtime/basicLock.hpp"
 #include "runtime/handles.hpp"
 #include "utilities/growableArray.hpp"
+#include "utilities/linkedlist.hpp"
+#include "utilities/resourceHash.hpp"
 
 class LogStream;
 class ObjectMonitor;
 class ThreadsList;
 
+// Hash table of JavaThread* to a list of ObjectMonitor* owned by the JavaThread*.
+//
+class ObjectMonitorsHashtable {
+ private:
+  static unsigned int ptr_hash(JavaThread* const& s1) {
+    // 2654435761 = 2^32 * Phi (golden ratio)
+    return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
+  }
+
+ public:
+  typedef LinkedListImpl<ObjectMonitor*,
+                         ResourceObj::C_HEAP, mtThread,
+                         AllocFailStrategy::RETURN_NULL> PtrList;
+
+  // ResourceHashtable SIZE is specified at compile time so we
+  // use 1031 which is the first prime after 1024.
+  typedef ResourceHashtable<JavaThread*, PtrList*, 1031,
+                            ResourceObj::C_HEAP, mtThread,
+                            &ObjectMonitorsHashtable::ptr_hash> PtrTable;
+ private:
+  PtrTable* _ptrs;
+  size_t _jt_count;
+  size_t _om_count;
+
+ public:
+  // ResourceHashtable is passed to various functions and populated in
+  // different places so we allocate it using C_HEAP to make it immune
+  // from any ResourceMarks that happen to be in the code paths.
+  ObjectMonitorsHashtable() : _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()), _jt_count(0), _om_count(0) {}
+
+  ~ObjectMonitorsHashtable();
+
+  void add_entry(JavaThread* jt, ObjectMonitor* om);
+
+  void add_entry(JavaThread* jt, PtrList* list) {
+    _ptrs->put(jt, list);
+    _jt_count++;
+  }
+
+  PtrList* get_entry(JavaThread* jt) {
+    PtrList** listpp = _ptrs->get(jt);
+    return (listpp == nullptr) ? nullptr : *listpp;
+  }
+
+  bool has_entry(JavaThread* jt) {
+    PtrList** listpp = _ptrs->get(jt);
+    return listpp != nullptr && *listpp != nullptr;
+  }
+
+  bool has_entry(JavaThread* jt, ObjectMonitor* om);
+
+  size_t jt_count() { return _jt_count; }
+  size_t om_count() { return _om_count; }
+};
+
 class MonitorList {
   friend class VMStructs;
 
@@ -133,21 +190,30 @@ class ObjectSynchronizer : AllStatic {
 
   // JNI detach support
   static void release_monitors_owned_by_thread(JavaThread* current);
+
+  // Iterate ObjectMonitors where the owner == thread; this does NOT include
+  // ObjectMonitors where owner is set to a stack lock address in thread:
+  //
+  // This version of monitors_iterate() works with the in-use monitor list.
   static void monitors_iterate(MonitorClosure* m, JavaThread* thread);
+  // This version of monitors_iterate() works with the specified linked list.
+  static void monitors_iterate(MonitorClosure* closure,
+                               ObjectMonitorsHashtable::PtrList* list,
+                               JavaThread* thread);
 
   // Initialize the gInflationLocks
   static void initialize();
 
-  // GC: we current use aggressive monitor deflation policy
+  // GC: we currently use aggressive monitor deflation policy
   // Basically we try to deflate all monitors that are not busy.
-  static size_t deflate_idle_monitors();
+  static size_t deflate_idle_monitors(ObjectMonitorsHashtable* table);
 
   // Deflate idle monitors:
   static void chk_for_block_req(JavaThread* current, const char* op_name,
                                 const char* cnt_name, size_t cnt, LogStream* ls,
                                 elapsedTimer* timer_p);
-  static size_t deflate_monitor_list(Thread* current, LogStream* ls,
-                                     elapsedTimer* timer_p);
+  static size_t deflate_monitor_list(Thread* current, LogStream* ls, elapsedTimer* timer_p,
+                                     ObjectMonitorsHashtable* table);
   static size_t in_use_list_ceiling();
   static void dec_in_use_list_ceiling();
   static void inc_in_use_list_ceiling();

src/hotspot/share/runtime/vmOperations.cpp

@@ -279,6 +279,18 @@ void VM_ThreadDump::doit() {
     concurrent_locks.dump_at_safepoint();
   }
 
+  ObjectMonitorsHashtable table;
+  ObjectMonitorsHashtable* tablep = nullptr;
+  if (_with_locked_monitors) {
+    // The caller wants locked monitor information and that's expensive to gather
+    // when there are a lot of inflated monitors. So we deflate idle monitors and
+    // gather information about owned monitors at the same time.
+    tablep = &table;
+    while (ObjectSynchronizer::deflate_idle_monitors(tablep) >= (size_t)MonitorDeflationMax) {
+      ; /* empty */
+    }
+  }
+
   if (_num_threads == 0) {
     // Snapshot all live threads
 
@@ -293,7 +305,7 @@ void VM_ThreadDump::doit() {
       if (_with_locked_synchronizers) {
         tcl = concurrent_locks.thread_concurrent_locks(jt);
       }
-      snapshot_thread(jt, tcl);
+      snapshot_thread(jt, tcl, tablep);
     }
   } else {
     // Snapshot threads in the given _threads array
@@ -328,14 +340,15 @@ void VM_ThreadDump::doit() {
       if (_with_locked_synchronizers) {
         tcl = concurrent_locks.thread_concurrent_locks(jt);
       }
-      snapshot_thread(jt, tcl);
+      snapshot_thread(jt, tcl, tablep);
     }
   }
 }
 
-void VM_ThreadDump::snapshot_thread(JavaThread* java_thread, ThreadConcurrentLocks* tcl) {
+void VM_ThreadDump::snapshot_thread(JavaThread* java_thread, ThreadConcurrentLocks* tcl,
+                                    ObjectMonitorsHashtable* table) {
   ThreadSnapshot* snapshot = _result->add_thread_snapshot(java_thread);
-  snapshot->dump_stack_at_safepoint(_max_depth, _with_locked_monitors);
+  snapshot->dump_stack_at_safepoint(_max_depth, _with_locked_monitors, table);
   snapshot->set_concurrent_locks(tcl);
 }
 

src/hotspot/share/runtime/vmOperations.hpp

@@ -207,7 +207,8 @@ class VM_ThreadDump : public VM_Operation {
   bool                           _with_locked_monitors;
   bool                           _with_locked_synchronizers;
 
-  void snapshot_thread(JavaThread* java_thread, ThreadConcurrentLocks* tcl);
+  void snapshot_thread(JavaThread* java_thread, ThreadConcurrentLocks* tcl,
+                       ObjectMonitorsHashtable* table);
 
  public:
   VM_ThreadDump(ThreadDumpResult* result,

src/hotspot/share/services/heapDumper.cpp

@@ -2388,7 +2388,7 @@ void VM_HeapDumper::dump_stack_traces() {
       HandleMark hm(current_thread);
 
       ThreadStackTrace* stack_trace = new ThreadStackTrace(thread, false);
-      stack_trace->dump_stack_at_safepoint(-1);
+      stack_trace->dump_stack_at_safepoint(-1, /* ObjectMonitorsHashtable is not needed here */ nullptr);
       _stack_traces[_num_threads++] = stack_trace;
 
       // write HPROF_FRAME records for this thread's stack trace

src/hotspot/share/services/threadService.cpp

@@ -659,7 +659,7 @@ ThreadStackTrace::~ThreadStackTrace() {
   }
 }
 
-void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth) {
+void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth, ObjectMonitorsHashtable* table) {
   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
 
   if (_thread->has_last_Java_frame()) {
@@ -683,9 +683,19 @@ void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth) {
 
   if (_with_locked_monitors) {
     // Iterate inflated monitors and find monitors locked by this thread
-    // not found in the stack
+    // that are not found in the stack, e.g. JNI locked monitors:
     InflatedMonitorsClosure imc(this);
-    ObjectSynchronizer::monitors_iterate(&imc, _thread);
+    if (table != nullptr) {
+      // Get the ObjectMonitors locked by the target thread, if any,
+      // and does not include any where owner is set to a stack lock
+      // address in the target thread:
+      ObjectMonitorsHashtable::PtrList* list = table->get_entry(_thread);
+      if (list != nullptr) {
+        ObjectSynchronizer::monitors_iterate(&imc, list, _thread);
+      }
+    } else {
+      ObjectSynchronizer::monitors_iterate(&imc, _thread);
+    }
   }
 }
 
@@ -936,9 +946,10 @@ ThreadSnapshot::~ThreadSnapshot() {
   delete _concurrent_locks;
 }
 
-void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors) {
+void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors,
+                                             ObjectMonitorsHashtable* table) {
   _stack_trace = new ThreadStackTrace(_thread, with_locked_monitors);
-  _stack_trace->dump_stack_at_safepoint(max_depth);
+  _stack_trace->dump_stack_at_safepoint(max_depth, table);
 }