8028498: runtime/SharedArchiveFile/CdsDifferentObjectAlignment.java asserts in RT_Baseline

Summary: Preventing GCs to occur before VM is completely initialized. This was previously partly done by one part of the GC locker which not was removed.
Reviewed-by: coleenp, pliden

src/share/vm/gc_implementation/shared/vmGCOperations.cpp

@@ -103,6 +103,15 @@ bool VM_GC_Operation::doit_prologue() {
   assert(((_gc_cause != GCCause::_no_gc) &&
           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
 
+  // To be able to handle a GC the VM initialization needs to be completed.
+  if (!is_init_completed()) {
+    vm_exit_during_initialization(
+      err_msg("GC triggered before VM initialization completed. Try increasing "
+              "NewSize, current value " UINTX_FORMAT "%s.",
+              byte_size_in_proper_unit(NewSize),
+              proper_unit_for_byte_size(NewSize)));
+  }
+
   acquire_pending_list_lock();
   // If the GC count has changed someone beat us to the collection
   // Get the Heap_lock after the pending_list_lock.

src/share/vm/memory/gcLocker.cpp

@@ -28,7 +28,6 @@
 #include "memory/sharedHeap.hpp"
 
 volatile jint GC_locker::_jni_lock_count = 0;
-volatile jint GC_locker::_lock_count     = 0;
 volatile bool GC_locker::_needs_gc       = false;
 volatile bool GC_locker::_doing_gc       = false;
 
@@ -102,7 +101,7 @@ void GC_locker::jni_lock(JavaThread* thread) {
   // We check that at least one thread is in a critical region before
   // blocking because blocked threads are woken up by a thread exiting
   // a JNI critical region.
-  while ((needs_gc() && is_jni_active()) || _doing_gc) {
+  while (is_active_and_needs_gc() || _doing_gc) {
     JNICritical_lock->wait();
   }
   thread->enter_critical();
@@ -116,27 +115,20 @@ void GC_locker::jni_unlock(JavaThread* thread) {
   _jni_lock_count--;
   decrement_debug_jni_lock_count();
   thread->exit_critical();
-  if (needs_gc() && !is_jni_active()) {
+  if (needs_gc() && !is_active_internal()) {
     // We're the last thread out. Cause a GC to occur.
-    // GC will also check is_active, so this check is not
-    // strictly needed. It's added here to make it clear that
-    // the GC will NOT be performed if any other caller
-    // of GC_locker::lock() still needs GC locked.
-    if (!is_active_internal()) {
-      _doing_gc = true;
-      {
-        // Must give up the lock while at a safepoint
-        MutexUnlocker munlock(JNICritical_lock);
-        if (PrintJNIGCStalls && PrintGCDetails) {
-          ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
-          gclog_or_tty->print_cr("%.3f: Thread \"%s\" is performing GC after exiting critical section, %d locked",
-                                 gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
-        }
-        Universe::heap()->collect(GCCause::_gc_locker);
+    _doing_gc = true;
+    {
+      // Must give up the lock while at a safepoint
+      MutexUnlocker munlock(JNICritical_lock);
+      if (PrintJNIGCStalls && PrintGCDetails) {
+        ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
+        gclog_or_tty->print_cr("%.3f: Thread \"%s\" is performing GC after exiting critical section, %d locked",
+            gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
       }
-      _doing_gc = false;
+      Universe::heap()->collect(GCCause::_gc_locker);
     }
-
+    _doing_gc = false;
     _needs_gc = false;
     JNICritical_lock->notify_all();
   }

src/share/vm/memory/gcLocker.hpp

@@ -54,8 +54,6 @@ class GC_locker: public AllStatic {
   // safepointing and decremented during the slow path of GC_locker
   // unlocking.
   static volatile jint _jni_lock_count;  // number of jni active instances.
-
-  static volatile jint _lock_count;      // number of other active instances
   static volatile bool _needs_gc;        // heap is filling, we need a GC
                                          // note: bool is typedef'd as jint
   static volatile bool _doing_gc;        // unlock_critical() is doing a GC
@@ -66,12 +64,6 @@ class GC_locker: public AllStatic {
   static volatile jint _debug_jni_lock_count;
 #endif
 
-  // Accessors
-  static bool is_jni_active() {
-    assert(_needs_gc, "only valid when _needs_gc is set");
-    return _jni_lock_count > 0;
-  }
-
   // At a safepoint, visit all threads and count the number of active
   // critical sections.  This is used to ensure that all active
   // critical sections are exited before a new one is started.
@@ -82,7 +74,7 @@ class GC_locker: public AllStatic {
 
   static bool is_active_internal() {
     verify_critical_count();
-    return _lock_count > 0 || _jni_lock_count > 0;
+    return _jni_lock_count > 0;
   }
 
  public:
@@ -132,10 +124,6 @@ class GC_locker: public AllStatic {
   // not a stable predicate.
   static void stall_until_clear();
 
-  // Non-structured GC locking: currently needed for JNI. Use with care!
-  static void lock();
-  static void unlock();
-
   // The following two methods are used for JNI critical regions.
   // If we find that we failed to perform a GC because the GC_locker
   // was active, arrange for one as soon as possible by allowing

src/share/vm/memory/gcLocker.inline.hpp

@@ -27,22 +27,6 @@
 
 #include "memory/gcLocker.hpp"
 
-inline void GC_locker::lock() {
-  // cast away volatile
-  Atomic::inc(&_lock_count);
-  CHECK_UNHANDLED_OOPS_ONLY(
-    if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; })
-  assert(Universe::heap() == NULL ||
-         !Universe::heap()->is_gc_active(), "locking failed");
-}
-
-inline void GC_locker::unlock() {
-  // cast away volatile
-  Atomic::dec(&_lock_count);
-  CHECK_UNHANDLED_OOPS_ONLY(
-    if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; })
-}
-
 inline void GC_locker::lock_critical(JavaThread* thread) {
   if (!thread->in_critical()) {
     if (needs_gc()) {

src/share/vm/memory/metaspaceShared.cpp

@@ -645,9 +645,6 @@ void MetaspaceShared::preload_and_dump(TRAPS) {
   TraceTime timer("Dump Shared Spaces", TraceStartupTime);
   ResourceMark rm;
 
-  // Lock out GC - is it necessary? I don't think we care.
-  No_GC_Verifier no_gc;
-
   // Preload classes to be shared.
   // Should use some os:: method rather than fopen() here. aB.
   // Construct the path to the class list (in jre/lib)

src/share/vm/memory/universe.cpp

@@ -632,7 +632,6 @@ jint universe_init() {
   guarantee(sizeof(oop) % sizeof(HeapWord) == 0,
             "oop size is not not a multiple of HeapWord size");
   TraceTime timer("Genesis", TraceStartupTime);
-  GC_locker::lock();  // do not allow gc during bootstrapping
   JavaClasses::compute_hard_coded_offsets();
 
   jint status = Universe::initialize_heap();
@@ -1164,8 +1163,6 @@ bool universe_post_init() {
 
   MemoryService::add_metaspace_memory_pools();
 
-  GC_locker::unlock();  // allow gc after bootstrapping
-
   MemoryService::set_universe_heap(Universe::_collectedHeap);
   return true;
 }

src/share/vm/runtime/thread.cpp

@@ -239,7 +239,6 @@ Thread::Thread() {
   debug_only(_allow_allocation_count = 0;)
   NOT_PRODUCT(_allow_safepoint_count = 0;)
   NOT_PRODUCT(_skip_gcalot = false;)
-  CHECK_UNHANDLED_OOPS_ONLY(_gc_locked_out_count = 0;)
   _jvmti_env_iteration_count = 0;
   set_allocated_bytes(0);
   _vm_operation_started_count = 0;

src/share/vm/runtime/thread.hpp

@@ -249,9 +249,6 @@ class Thread: public ThreadShadow {
   // Used by SkipGCALot class.
   NOT_PRODUCT(bool _skip_gcalot;)               // Should we elide gc-a-lot?
 
-  // Record when GC is locked out via the GC_locker mechanism
-  CHECK_UNHANDLED_OOPS_ONLY(int _gc_locked_out_count;)
-
   friend class No_Alloc_Verifier;
   friend class No_Safepoint_Verifier;
   friend class Pause_No_Safepoint_Verifier;
@@ -397,7 +394,6 @@ class Thread: public ThreadShadow {
   void clear_unhandled_oops() {
     if (CheckUnhandledOops) unhandled_oops()->clear_unhandled_oops();
   }
-  bool is_gc_locked_out() { return _gc_locked_out_count > 0; }
 #endif // CHECK_UNHANDLED_OOPS
 
 #ifndef PRODUCT

src/share/vm/runtime/unhandledOops.cpp

@@ -113,9 +113,7 @@ void UnhandledOops::unregister_unhandled_oop(oop* op) {
 
 void UnhandledOops::clear_unhandled_oops() {
   assert (CheckUnhandledOops, "should only be called with checking option");
-  if (_thread->is_gc_locked_out()) {
-    return;
-  }
+
   for (int k = 0; k < _oop_list->length(); k++) {
     UnhandledOopEntry entry = _oop_list->at(k);
     // If an entry is on the unhandled oop list but isn't on the stack