src/hotspot/share/gc/z/zHeap.cpp

*** 38,47 ****
--- 38,48 ----
  #include "gc/z/zVerify.hpp"
  #include "gc/z/zWorkers.inline.hpp"
  #include "logging/log.hpp"
  #include "memory/iterator.hpp"
  #include "memory/resourceArea.hpp"
+ #include "runtime/handshake.hpp"
  #include "runtime/safepoint.hpp"
  #include "runtime/thread.hpp"
  #include "utilities/debug.hpp"
  
  static const ZStatSampler ZSamplerHeapUsedBeforeMark("Memory", "Heap Used Before Mark", ZStatUnitBytes);
*** 313,341 ****
    ZResurrection::block();
  
    // Process weak roots
    _weak_roots_processor.process_weak_roots();
  
!   // Prepare to unload unused classes and code
    _unload.prepare();
  
    return true;
  }
  
  void ZHeap::set_soft_reference_policy(bool clear) {
    _reference_processor.set_soft_reference_policy(clear);
  }
  
  void ZHeap::process_non_strong_references() {
    // Process Soft/Weak/Final/PhantomReferences
    _reference_processor.process_references();
  
    // Process concurrent weak roots
    _weak_roots_processor.process_concurrent_weak_roots();
  
!   // Unload unused classes and code
!   _unload.unload();
  
    // Unblock resurrection of weak/phantom references
    ZResurrection::unblock();
  
    // Enqueue Soft/Weak/Final/PhantomReferences. Note that this
--- 314,361 ----
    ZResurrection::block();
  
    // Process weak roots
    _weak_roots_processor.process_weak_roots();
  
!   // Prepare to unload stale metadata and nmethods
    _unload.prepare();
  
    return true;
  }
  
  void ZHeap::set_soft_reference_policy(bool clear) {
    _reference_processor.set_soft_reference_policy(clear);
  }
  
+ class ZRendezvousClosure : public ThreadClosure {
+ public:
+   virtual void do_thread(Thread* thread) {}
+ };
+ 
  void ZHeap::process_non_strong_references() {
    // Process Soft/Weak/Final/PhantomReferences
    _reference_processor.process_references();
  
    // Process concurrent weak roots
    _weak_roots_processor.process_concurrent_weak_roots();
  
!   // Unlink stale metadata and nmethods
!   _unload.unlink();
! 
!   // Perform a handshake. This is needed 1) to make sure that stale
!   // metadata and nmethods are no longer observable. And 2), to
!   // prevent the race where a mutator first loads an oop, which is
!   // logically null but not yet cleared. Then this oop gets cleared
!   // by the reference processor and resurrection is unblocked. At
!   // this point the mutator could see the unblocked state and pass
!   // this invalid oop through the normal barrier path, which would
!   // incorrectly try to mark the oop.
!   ZRendezvousClosure cl;
!   Handshake::execute(&cl);
! 
!   // Purge stale metadata and nmethods that were unlinked
!   _unload.purge();
  
    // Unblock resurrection of weak/phantom references
    ZResurrection::unblock();
  
    // Enqueue Soft/Weak/Final/PhantomReferences. Note that this
*** 403,413 ****
  }
  
  void ZHeap::relocate_start() {
    assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
  
!   // Finish unloading of classes and code
    _unload.finish();
  
    // Flip address view
    flip_to_remapped();
  
--- 423,433 ----
  }
  
  void ZHeap::relocate_start() {
    assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
  
!   // Finish unloading stale metadata and nmethods
    _unload.finish();
  
    // Flip address view
    flip_to_remapped();