src/hotspot/share/code/nmethod.cpp

*** 1659,1682 ****
  // Even if it is the end of the linked list, it will have a non-null link value,
  // as long as it is on the list.
  // This code must be MP safe, because it is used from parallel GC passes.
  bool nmethod::test_set_oops_do_mark() {
    assert(nmethod::oops_do_marking_is_active(), "oops_do_marking_prologue must be called");
!   nmethod* observed_mark_link = _oops_do_mark_link;
!   if (observed_mark_link == NULL) {
      // Claim this nmethod for this thread to mark.
!     observed_mark_link = (nmethod*)
!       Atomic::cmpxchg_ptr(NMETHOD_SENTINEL, &_oops_do_mark_link, NULL);
!     if (observed_mark_link == NULL) {
! 
        // Atomically append this nmethod (now claimed) to the head of the list:
        nmethod* observed_mark_nmethods = _oops_do_mark_nmethods;
        for (;;) {
          nmethod* required_mark_nmethods = observed_mark_nmethods;
          _oops_do_mark_link = required_mark_nmethods;
!         observed_mark_nmethods = (nmethod*)
!           Atomic::cmpxchg_ptr(this, &_oops_do_mark_nmethods, required_mark_nmethods);
          if (observed_mark_nmethods == required_mark_nmethods)
            break;
        }
        // Mark was clear when we first saw this guy.
        if (TraceScavenge) { print_on(tty, "oops_do, mark"); }
--- 1659,1678 ----
  // Even if it is the end of the linked list, it will have a non-null link value,
  // as long as it is on the list.
  // This code must be MP safe, because it is used from parallel GC passes.
  bool nmethod::test_set_oops_do_mark() {
    assert(nmethod::oops_do_marking_is_active(), "oops_do_marking_prologue must be called");
!   if (_oops_do_mark_link == NULL) {
      // Claim this nmethod for this thread to mark.
!     if (Atomic::cmpxchg(NMETHOD_SENTINEL, &_oops_do_mark_link, (nmethod*)NULL) == NULL) {
        // Atomically append this nmethod (now claimed) to the head of the list:
        nmethod* observed_mark_nmethods = _oops_do_mark_nmethods;
        for (;;) {
          nmethod* required_mark_nmethods = observed_mark_nmethods;
          _oops_do_mark_link = required_mark_nmethods;
!         observed_mark_nmethods =
!           Atomic::cmpxchg(this, &_oops_do_mark_nmethods, required_mark_nmethods);
          if (observed_mark_nmethods == required_mark_nmethods)
            break;
        }
        // Mark was clear when we first saw this guy.
        if (TraceScavenge) { print_on(tty, "oops_do, mark"); }
*** 1688,1700 ****
  }
  
  void nmethod::oops_do_marking_prologue() {
    if (TraceScavenge) { tty->print_cr("[oops_do_marking_prologue"); }
    assert(_oops_do_mark_nmethods == NULL, "must not call oops_do_marking_prologue twice in a row");
!   // We use cmpxchg_ptr instead of regular assignment here because the user
    // may fork a bunch of threads, and we need them all to see the same state.
!   void* observed = Atomic::cmpxchg_ptr(NMETHOD_SENTINEL, &_oops_do_mark_nmethods, NULL);
    guarantee(observed == NULL, "no races in this sequential code");
  }
  
  void nmethod::oops_do_marking_epilogue() {
    assert(_oops_do_mark_nmethods != NULL, "must not call oops_do_marking_epilogue twice in a row");
--- 1684,1696 ----
  }
  
  void nmethod::oops_do_marking_prologue() {
    if (TraceScavenge) { tty->print_cr("[oops_do_marking_prologue"); }
    assert(_oops_do_mark_nmethods == NULL, "must not call oops_do_marking_prologue twice in a row");
!   // We use cmpxchg instead of regular assignment here because the user
    // may fork a bunch of threads, and we need them all to see the same state.
!   nmethod* observed = Atomic::cmpxchg(NMETHOD_SENTINEL, &_oops_do_mark_nmethods, (nmethod*)NULL);
    guarantee(observed == NULL, "no races in this sequential code");
  }
  
  void nmethod::oops_do_marking_epilogue() {
    assert(_oops_do_mark_nmethods != NULL, "must not call oops_do_marking_epilogue twice in a row");
*** 1705,1716 ****
      cur->_oops_do_mark_link = NULL;
      DEBUG_ONLY(cur->verify_oop_relocations());
      NOT_PRODUCT(if (TraceScavenge)  cur->print_on(tty, "oops_do, unmark"));
      cur = next;
    }
!   void* required = _oops_do_mark_nmethods;
!   void* observed = Atomic::cmpxchg_ptr(NULL, &_oops_do_mark_nmethods, required);
    guarantee(observed == required, "no races in this sequential code");
    if (TraceScavenge) { tty->print_cr("oops_do_marking_epilogue]"); }
  }
  
  class DetectScavengeRoot: public OopClosure {
--- 1701,1712 ----
      cur->_oops_do_mark_link = NULL;
      DEBUG_ONLY(cur->verify_oop_relocations());
      NOT_PRODUCT(if (TraceScavenge)  cur->print_on(tty, "oops_do, unmark"));
      cur = next;
    }
!   nmethod* required = _oops_do_mark_nmethods;
!   nmethod* observed = Atomic::cmpxchg((nmethod*)NULL, &_oops_do_mark_nmethods, required);
    guarantee(observed == required, "no races in this sequential code");
    if (TraceScavenge) { tty->print_cr("oops_do_marking_epilogue]"); }
  }
  
  class DetectScavengeRoot: public OopClosure {