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src/hotspot/share/runtime/objectMonitor.cpp
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rev 54612 : Checkpoint latest preliminary review patches for full OpenJDK review; merge with 8222295.patch.
rev 54613 : imported patch dcubed.monitor_deflate_conc.v2.01
rev 54614 : imported patch dcubed.monitor_deflate_conc.v2.02
rev 54615 : imported patch dcubed.monitor_deflate_conc.v2.03
@@ -236,36 +236,38 @@
}
// -----------------------------------------------------------------------------
// Enter support
-bool ObjectMonitor::enter(TRAPS) {
+void ObjectMonitor::enter(TRAPS) {
+ ADIM_guarantee(_ref_count > 0, "must be positive: ref_count=%d", _ref_count);
+
// The following code is ordered to check the most common cases first
// and to reduce RTS->RTO cache line upgrades on SPARC and IA32 processors.
Thread * const Self = THREAD;
void * cur = Atomic::cmpxchg(Self, &_owner, (void*)NULL);
if (cur == NULL) {
// Either ASSERT _recursions == 0 or explicitly set _recursions = 0.
assert(_recursions == 0, "invariant");
assert(_owner == Self, "invariant");
- return true;
+ return;
}
if (cur == Self) {
// TODO-FIXME: check for integer overflow! BUGID 6557169.
_recursions++;
- return true;
+ return;
}
if (Self->is_lock_owned ((address)cur)) {
assert(_recursions == 0, "internal state error");
_recursions = 1;
// Commute owner from a thread-specific on-stack BasicLockObject address to
// a full-fledged "Thread *".
_owner = Self;
- return true;
+ return;
}
// We've encountered genuine contention.
assert(Self->_Stalled == 0, "invariant");
Self->_Stalled = intptr_t(this);
@@ -282,35 +284,27 @@
assert(((oop)object())->mark() == markOopDesc::encode(this),
"object mark must match encoded this: mark=" INTPTR_FORMAT
", encoded this=" INTPTR_FORMAT, p2i(((oop)object())->mark()),
p2i(markOopDesc::encode(this)));
Self->_Stalled = 0;
- return true;
+ return;
}
assert(_owner != Self, "invariant");
assert(_succ != Self, "invariant");
assert(Self->is_Java_thread(), "invariant");
JavaThread * jt = (JavaThread *) Self;
assert(!SafepointSynchronize::is_at_safepoint(), "invariant");
assert(jt->thread_state() != _thread_blocked, "invariant");
assert(AsyncDeflateIdleMonitors || this->object() != NULL, "invariant");
- assert(AsyncDeflateIdleMonitors || _contentions >= 0, "invariant");
+ assert(_contentions >= 0, "must not be negative: contentions=%d", _contentions);
- // Prevent deflation. See ObjectSynchronizer::deflate_monitor() and is_busy().
- // Ensure the object-monitor relationship remains stable while there's contention.
- const jint contentions = Atomic::add(1, &_contentions);
- if (contentions <= 0 && _owner == DEFLATER_MARKER) {
- // Async deflation is in progress. Attempt to restore the
- // header/dmw to the object's header so that we only retry once
- // if the deflater thread happens to be slow.
- const oop obj = (oop) object();
- install_displaced_markword_in_object(obj);
- Self->_Stalled = 0;
- return false; // Caller should retry. Never mind about _contentions as this monitor has been deflated.
- }
- // The deflater thread will not deflate this monitor and the monitor is contended, continue.
+ // Prevent deflation. See ObjectSynchronizer::deflate_monitor(),
+ // ObjectSynchronizer::deflate_monitor_using_JT() and is_busy().
+ // Ensure the object <-> monitor relationship remains stable while
+ // there's contention.
+ Atomic::add(1, &_contentions);
JFR_ONLY(JfrConditionalFlushWithStacktrace<EventJavaMonitorEnter> flush(jt);)
EventJavaMonitorEnter event;
if (event.should_commit()) {
event.set_monitorClass(((oop)this->object())->klass());
@@ -368,11 +362,11 @@
// states will still report that the thread is blocked trying to
// acquire it.
}
Atomic::dec(&_contentions);
- assert(AsyncDeflateIdleMonitors || _contentions >= 0, "invariant");
+ assert(_contentions >= 0, "must not be negative: contentions=%d", _contentions);
Self->_Stalled = 0;
// Must either set _recursions = 0 or ASSERT _recursions == 0.
assert(_recursions == 0, "invariant");
assert(_owner == Self, "invariant");
@@ -404,11 +398,10 @@
if (event.should_commit()) {
event.set_previousOwner((uintptr_t)_previous_owner_tid);
event.commit();
}
OM_PERFDATA_OP(ContendedLockAttempts, inc());
- return true;
}
// Caveat: TryLock() is not necessarily serializing if it returns failure.
// Callers must compensate as needed.
@@ -433,11 +426,11 @@
// idempotent method is called by a thread that is deflating a
// monitor and by other threads that have detected a race with the
// deflation process.
void ObjectMonitor::install_displaced_markword_in_object(const oop obj) {
// This function must only be called when (owner == DEFLATER_MARKER
- // && contentions <= 0), but we can't guarantee that here because
+ // && ref_count <= 0), but we can't guarantee that here because
// those values could change when the ObjectMonitor gets moved from
// the global free list to a per-thread free list.
guarantee(obj != NULL, "must be non-NULL");
if (object() != obj) {
@@ -508,10 +501,12 @@
}
#define MAX_RECHECK_INTERVAL 1000
void ObjectMonitor::EnterI(TRAPS) {
+ ADIM_guarantee(_ref_count > 0, "must be positive: ref_count=%d", _ref_count);
+
Thread * const Self = THREAD;
assert(Self->is_Java_thread(), "invariant");
assert(((JavaThread *) Self)->thread_state() == _thread_blocked, "invariant");
// Try the lock - TATAS
@@ -521,16 +516,12 @@
assert(_Responsible != Self, "invariant");
return;
}
if (_owner == DEFLATER_MARKER) {
- // The deflation protocol finished the first part (setting _owner), but
- // it failed the second part (making _contentions negative) and bailed.
- // Because we're called from enter() we have at least one contention.
- guarantee(_contentions > 0, "owner == DEFLATER_MARKER && contentions <= 0 "
- "should have been handled by the caller: contentions=%d",
- _contentions);
+ // The deflation protocol finished the first part (setting owner), but
+ // it failed the second part (making ref_count negative) and bailed.
if (Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
// Acquired the monitor.
assert(_succ != Self, "invariant");
assert(_Responsible != Self, "invariant");
return;
@@ -652,16 +643,12 @@
}
if (TryLock(Self) > 0) break;
if (_owner == DEFLATER_MARKER) {
- // The deflation protocol finished the first part (setting _owner), but
- // it failed the second part (making _contentions negative) and bailed.
- // Because we're called from enter() we have at least one contention.
- guarantee(_contentions > 0, "owner == DEFLATER_MARKER && contentions <= 0 "
- "should have been handled by the caller: contentions=%d",
- _contentions);
+ // The deflation protocol finished the first part (setting owner), but
+ // it failed the second part (making ref_count negative) and bailed.
if (Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
// Acquired the monitor.
break;
}
}
@@ -768,10 +755,12 @@
// monitor reentry in wait().
//
// In the future we should reconcile EnterI() and ReenterI().
void ObjectMonitor::ReenterI(Thread * Self, ObjectWaiter * SelfNode) {
+ ADIM_guarantee(_ref_count > 0, "must be positive: ref_count=%d", _ref_count);
+
assert(Self != NULL, "invariant");
assert(SelfNode != NULL, "invariant");
assert(SelfNode->_thread == Self, "invariant");
assert(_waiters > 0, "invariant");
assert(((oop)(object()))->mark() == markOopDesc::encode(this), "invariant");
@@ -786,16 +775,12 @@
if (TryLock(Self) > 0) break;
if (TrySpin(Self) > 0) break;
if (_owner == DEFLATER_MARKER) {
- // The deflation protocol finished the first part (setting _owner),
- // but it will observe _waiters != 0 and will bail out. Because we're
- // called from wait() we may or may not have any contentions.
- guarantee(_contentions >= 0, "owner == DEFLATER_MARKER && contentions < 0 "
- "should have been handled by the caller: contentions=%d",
- _contentions);
+ // The deflation protocol finished the first part (setting owner), but
+ // it failed the second part (making ref_count negative) and bailed.
if (Atomic::cmpxchg(Self, &_owner, DEFLATER_MARKER) == DEFLATER_MARKER) {
// Acquired the monitor.
break;
}
}
@@ -1256,24 +1241,20 @@
return save;
}
// reenter() enters a lock and sets recursion count
// complete_exit/reenter operate as a wait without waiting
-bool ObjectMonitor::reenter(intptr_t recursions, TRAPS) {
+void ObjectMonitor::reenter(intptr_t recursions, TRAPS) {
Thread * const Self = THREAD;
assert(Self->is_Java_thread(), "Must be Java thread!");
JavaThread *jt = (JavaThread *)THREAD;
guarantee(_owner != Self, "reenter already owner");
- if (!enter(THREAD)) {
- // Failed to enter the monitor so return for a retry.
- return false;
- }
+ enter(THREAD);
// Entered the monitor.
guarantee(_recursions == 0, "reenter recursion");
_recursions = recursions;
- return true;
}
// -----------------------------------------------------------------------------
// A macro is used below because there may already be a pending
@@ -1497,12 +1478,11 @@
Self->_Stalled = 0;
assert(_owner != Self, "invariant");
ObjectWaiter::TStates v = node.TState;
if (v == ObjectWaiter::TS_RUN) {
- const bool success = enter(Self);
- ADIM_guarantee(success, "enter signaled for a retry, but monitor should not have been deflated as waiters > 0");
+ enter(Self);
} else {
guarantee(v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ, "invariant");
ReenterI(Self, &node);
node.wait_reenter_end(this);
}
@@ -2062,11 +2042,11 @@
}
DEBUG_ONLY(InitDone = true;)
}
-// For internal used by ObjectSynchronizer::monitors_iterate().
+// For internal use by ObjectSynchronizer::monitors_iterate().
ObjectMonitorHandle::ObjectMonitorHandle(ObjectMonitor * om_ptr) {
om_ptr->inc_ref_count();
_om_ptr = om_ptr;
}
@@ -2096,22 +2076,19 @@
if (AsyncDeflateIdleMonitors) {
// Race here if monitor is not owned! The above ref_count bump
// will cause subsequent async deflation to skip it. However,
// previous or concurrent async deflation is a race.
- if (om_ptr->_owner == DEFLATER_MARKER && om_ptr->_contentions <= 0) {
- // Async deflation is in progress.
- if (om_ptr->ref_count() <= 0) {
- // And our ref_count increment above lost the race to async
- // deflation. Attempt to restore the header/dmw to the
- // object's header so that we only retry once if the deflater
- // thread happens to be slow.
+ if (om_ptr->_owner == DEFLATER_MARKER && om_ptr->ref_count() <= 0) {
+ // Async deflation is in progress and our ref_count increment
+ // above lost the race to async deflation. Attempt to restore
+ // the header/dmw to the object's header so that we only retry
+ // once if the deflater thread happens to be slow.
om_ptr->install_displaced_markword_in_object(object);
om_ptr->dec_ref_count();
return false;
}
- }
// The ObjectMonitor could have been deflated and reused for
// another object before we bumped the ref_count so make sure
// our object still refers to this ObjectMonitor.
const markOop tmp = object->mark();
if (!tmp->has_monitor() || tmp->monitor() != om_ptr) {
@@ -2120,23 +2097,23 @@
om_ptr->dec_ref_count();
return false;
}
}
- guarantee(_om_ptr == NULL, "sanity check: _om_ptr=" INTPTR_FORMAT,
+ ADIM_guarantee(_om_ptr == NULL, "sanity check: _om_ptr=" INTPTR_FORMAT,
p2i(_om_ptr));
_om_ptr = om_ptr;
return true;
}
// For internal use by ObjectSynchronizer::inflate().
void ObjectMonitorHandle::set_om_ptr(ObjectMonitor * om_ptr) {
if (_om_ptr == NULL) {
- guarantee(om_ptr != NULL, "cannot clear an unset om_ptr");
+ ADIM_guarantee(om_ptr != NULL, "cannot clear an unset om_ptr");
om_ptr->inc_ref_count();
_om_ptr = om_ptr;
} else {
- guarantee(om_ptr == NULL, "can only clear a set om_ptr");
+ ADIM_guarantee(om_ptr == NULL, "can only clear a set om_ptr");
_om_ptr->dec_ref_count();
_om_ptr = NULL;
}
}
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