1.1 --- a/src/share/vm/runtime/biasedLocking.cpp Wed Nov 12 11:23:13 2008 -0500
1.2 +++ b/src/share/vm/runtime/biasedLocking.cpp Fri Nov 21 08:09:11 2008 -0800
1.3 @@ -582,13 +582,19 @@
1.4 if (heuristics == HR_NOT_BIASED) {
1.5 return NOT_BIASED;
1.6 } else if (heuristics == HR_SINGLE_REVOKE) {
1.7 - if (mark->biased_locker() == THREAD) {
1.8 + Klass *k = Klass::cast(obj->klass());
1.9 + markOop prototype_header = k->prototype_header();
1.10 + if (mark->biased_locker() == THREAD &&
1.11 + prototype_header->bias_epoch() == mark->bias_epoch()) {
1.12 // A thread is trying to revoke the bias of an object biased
1.13 // toward it, again likely due to an identity hash code
1.14 // computation. We can again avoid a safepoint in this case
1.15 // since we are only going to walk our own stack. There are no
1.16 // races with revocations occurring in other threads because we
1.17 // reach no safepoints in the revocation path.
1.18 + // Also check the epoch because even if threads match, another thread
1.19 + // can come in with a CAS to steal the bias of an object that has a
1.20 + // stale epoch.
1.21 ResourceMark rm;
1.22 if (TraceBiasedLocking) {
1.23 tty->print_cr("Revoking bias by walking my own stack:");
