jdk-sandbox: comparison src/hotspot/share/runtime/biasedLocking.cpp

equal deleted inserted replaced

-:cb90a20eb99a
+:f7e8dbb77156
 // possibility of calls to BiasedLocking::enabled() before
 // BiasedLocking::init().
 return _biased_locking_enabled || BiasedLockingStartupDelay == 0;
 }
 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order
 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) {
 GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info();
 if (info != NULL) {
 return info;
 thread->set_cached_monitor_info(info);
 return info;
 }
 // After the call, *biased_locker will be set to obj->mark()->biased_locker() if biased_locker != NULL,
 // AND it is a living thread. Otherwise it will not be updated, (i.e. the caller is responsible for initialization).
-static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread, JavaThread** biased_locker) {
+BiasedLocking::Condition BiasedLocking::single_revoke_at_safepoint(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread, JavaThread** biased_locker) {
+assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
+assert(Thread::current()->is_VM_thread(), "must be VMThread");
 markOop mark = obj->mark();
 if (!mark->has_bias_pattern()) {
 if (log_is_enabled(Info, biasedlocking)) {
 ResourceMark rm;
 log_info(biasedlocking)("  (Skipping revocation of object " INTPTR_FORMAT
 " because it's no longer biased)",
 p2i((void *)obj), (intptr_t) mark,
 obj->klass()->external_name(),
 (intptr_t) requesting_thread);
 }
-return BiasedLocking::NOT_BIASED;
+return NOT_BIASED;
 }
 uint age = mark->age();
 markOop   biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age);
 markOop unbiased_prototype = markOopDesc::prototype()->set_age(age);
 if (!is_bulk) {
 log_info(biasedlocking)("  Revoked bias of anonymously-biased object");
 } else {
 log_trace(biasedlocking)("  Revoked bias of anonymously-biased object");
 }
-return BiasedLocking::BIAS_REVOKED;
+return BIAS_REVOKED;
 }
 // Handle case where the thread toward which the object was biased has exited
 bool thread_is_alive = false;
 if (requesting_thread == biased_thread) {
 PTR_FORMAT ")", p2i(biased_thread));
 } else {
 log_trace(biasedlocking)("  Revoked bias of object biased toward dead thread ("
 PTR_FORMAT ")", p2i(biased_thread));
 }
-return BiasedLocking::BIAS_REVOKED;
+return BIAS_REVOKED;
 }
 // Log at "info" level if not bulk, else "trace" level
 if (!is_bulk) {
 log_info(biasedlocking)("  Revoked bias of object biased toward live thread ("
 MonitorInfo* mon_info = cached_monitor_info->at(i);
 if (oopDesc::equals(mon_info->owner(), obj)) {
 log_trace(biasedlocking)("   mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")",
 p2i((void *) mon_info->owner()),
 p2i((void *) obj));
-// Assume recursive case and fix up highest lock later
+// Assume recursive case and fix up highest lock below
 markOop mark = markOopDesc::encode((BasicLock*) NULL);
 highest_lock = mon_info->lock();
 highest_lock->set_displaced_header(mark);
 } else {
 log_trace(biasedlocking)("   mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")",
 if (highest_lock != NULL) {
 // Fix up highest lock to contain displaced header and point
 // object at it
 highest_lock->set_displaced_header(unbiased_prototype);
 // Reset object header to point to displaced mark.
-// Must release storing the lock address for platforms without TSO
+// Must release store the lock address for platforms without TSO
 // ordering (e.g. ppc).
 obj->release_set_mark(markOopDesc::encode(highest_lock));
 assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit");
 // Log at "info" level if not bulk, else "trace" level
 if (!is_bulk) {
 // If requested, return information on which thread held the bias
 if (biased_locker != NULL) {
 *biased_locker = biased_thread;
 }
-return BiasedLocking::BIAS_REVOKED;
+return BIAS_REVOKED;
 }
 enum HeuristicsResult {
 HR_NOT_BIASED    = 1,
 HR_BULK_REBIAS   = 3,
 HR_BULK_REVOKE   = 4
 };
-static HeuristicsResult update_heuristics(oop o, bool allow_rebias) {
+static HeuristicsResult update_heuristics(oop o) {
 markOop mark = o->mark();
 if (!mark->has_bias_pattern()) {
 return HR_NOT_BIASED;
 }
 return HR_SINGLE_REVOKE;
 }
-static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o,
+BiasedLocking::Condition BiasedLocking::bulk_revoke_or_rebias_at_safepoint(oop o,
 bool bulk_rebias,
 bool attempt_rebias_of_object,
 JavaThread* requesting_thread) {
 assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
+assert(Thread::current()->is_VM_thread(), "must be VMThread");
 log_info(biasedlocking)("* Beginning bulk revocation (kind == %s) because of object "
 INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
 (bulk_rebias ? "rebias" : "revoke"),
 p2i((void *) o),
 (intptr_t) o->mark(),
 o->klass()->external_name());
 jlong cur_time = os::javaTimeMillis();
 o->klass()->set_last_biased_lock_bulk_revocation_time(cur_time);
 Klass* k_o = o->klass();
 Klass* klass = k_o;
 {
 }
 }
 // At this point we're done. All we have to do is potentially
 // adjust the header of the given object to revoke its bias.
-revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread, NULL);
+single_revoke_at_safepoint(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread, NULL);
 } else {
 if (log_is_enabled(Info, biasedlocking)) {
 ResourceMark rm;
 log_info(biasedlocking)("* Disabling biased locking for type %s", klass->external_name());
 }
 for (int i = 0; i < cached_monitor_info->length(); i++) {
 MonitorInfo* mon_info = cached_monitor_info->at(i);
 oop owner = mon_info->owner();
 markOop mark = owner->mark();
 if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
-revoke_bias(owner, false, true, requesting_thread, NULL);
+single_revoke_at_safepoint(owner, false, true, requesting_thread, NULL);
 }
 }
 }
 // Must force the bias of the passed object to be forcibly revoked
 // as well to ensure guarantees to callers
-revoke_bias(o, false, true, requesting_thread, NULL);
+single_revoke_at_safepoint(o, false, true, requesting_thread, NULL);
 }
 } // ThreadsListHandle is destroyed here.
 log_info(biasedlocking)("* Ending bulk revocation");
-BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED;
+BiasedLocking::Condition status_code = BIAS_REVOKED;
 if (attempt_rebias_of_object &&
 o->mark()->has_bias_pattern() &&
 klass->prototype_header()->has_bias_pattern()) {
 markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(),
 klass->prototype_header()->bias_epoch());
 o->set_mark(new_mark);
-status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED;
+status_code = BIAS_REVOKED_AND_REBIASED;
 log_info(biasedlocking)("  Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread);
 }
 assert(!o->mark()->has_bias_pattern() ||
 (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)),
 return status_code;
 }
-static void clean_up_cached_monitor_info() {
+static void clean_up_cached_monitor_info(JavaThread* thread = NULL) {
-// Walk the thread list clearing out the cached monitors
+if (thread != NULL) {
-for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
+thread->set_cached_monitor_info(NULL);
-thr->set_cached_monitor_info(NULL);
+} else {
-}
+// Walk the thread list clearing out the cached monitors
-}
+for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
+thr->set_cached_monitor_info(NULL);
+}
-class VM_RevokeBias : public VM_Operation {
+}
-protected:
+}
+class VM_BulkRevokeBias : public VM_Operation {
+private:
 Handle* _obj;
-GrowableArray<Handle>* _objs;
 JavaThread* _requesting_thread;
-BiasedLocking::Condition _status_code;
-traceid _biased_locker_id;
-uint64_t _safepoint_id;
-public:
-VM_RevokeBias(Handle* obj, JavaThread* requesting_thread)
-: _obj(obj)
-, _objs(NULL)
-, _requesting_thread(requesting_thread)
-, _status_code(BiasedLocking::NOT_BIASED)
-, _biased_locker_id(0)
-, _safepoint_id(0) {}
-VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread)
-: _obj(NULL)
-, _objs(objs)
-, _requesting_thread(requesting_thread)
-, _status_code(BiasedLocking::NOT_BIASED)
-, _biased_locker_id(0)
-, _safepoint_id(0) {}
-virtual VMOp_Type type() const { return VMOp_RevokeBias; }
-virtual bool doit_prologue() {
-// Verify that there is actual work to do since the callers just
-// give us locked object(s). If we don't find any biased objects
-// there is nothing to do and we avoid a safepoint.
-if (_obj != NULL) {
-markOop mark = (*_obj)()->mark();
-if (mark->has_bias_pattern()) {
-return true;
-}
-} else {
-for ( int i = 0 ; i < _objs->length(); i++ ) {
-markOop mark = (_objs->at(i))()->mark();
-if (mark->has_bias_pattern()) {
-return true;
-}
-}
-}
-return false;
-}
-virtual void doit() {
-if (_obj != NULL) {
-log_info(biasedlocking)("Revoking bias with potentially per-thread safepoint:");
-JavaThread* biased_locker = NULL;
-_status_code = revoke_bias((*_obj)(), false, false, _requesting_thread, &biased_locker);
-if (biased_locker != NULL) {
-_biased_locker_id = JFR_THREAD_ID(biased_locker);
-}
-_safepoint_id = SafepointSynchronize::safepoint_id();
-clean_up_cached_monitor_info();
-return;
-} else {
-log_info(biasedlocking)("Revoking bias with global safepoint:");
-BiasedLocking::revoke_at_safepoint(_objs);
-}
-}
-BiasedLocking::Condition status_code() const {
-return _status_code;
-}
-traceid biased_locker() const {
-return _biased_locker_id;
-}
-uint64_t safepoint_id() const {
-return _safepoint_id;
-}
-};
-class VM_BulkRevokeBias : public VM_RevokeBias {
-private:
 bool _bulk_rebias;
 bool _attempt_rebias_of_object;
+BiasedLocking::Condition _status_code;
+uint64_t _safepoint_id;
 public:
 VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread,
 bool bulk_rebias,
 bool attempt_rebias_of_object)
-: VM_RevokeBias(obj, requesting_thread)
+: _obj(obj)
+, _requesting_thread(requesting_thread)
 , _bulk_rebias(bulk_rebias)
-, _attempt_rebias_of_object(attempt_rebias_of_object) {}
+, _attempt_rebias_of_object(attempt_rebias_of_object)
+, _status_code(BiasedLocking::NOT_BIASED)
+, _safepoint_id(0) {}
 virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; }
-virtual bool doit_prologue()   { return true; }
 virtual void doit() {
-_status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread);
+_status_code = BiasedLocking::bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread);
 _safepoint_id = SafepointSynchronize::safepoint_id();
 clean_up_cached_monitor_info();
 }
 bool is_bulk_rebias() const {
 return _bulk_rebias;
 }
+BiasedLocking::Condition status_code() const {
+return _status_code;
+}
+uint64_t safepoint_id() const {
+return _safepoint_id;
+}
 };
+class RevokeOneBias : public ThreadClosure {
+protected:
+Handle _obj;
+JavaThread* _requesting_thread;
+JavaThread* _biased_locker;
+BiasedLocking::Condition _status_code;
+traceid _biased_locker_id;
+public:
+RevokeOneBias(Handle obj, JavaThread* requesting_thread, JavaThread* biased_locker)
+: _obj(obj)
+, _requesting_thread(requesting_thread)
+, _biased_locker(biased_locker)
+, _status_code(BiasedLocking::NOT_BIASED)
+, _biased_locker_id(0) {}
+void do_thread(Thread* target) {
+assert(target == _biased_locker, "Wrong thread");
+oop o = _obj();
+markOop mark = o->mark();
+if (!mark->has_bias_pattern()) {
+return;
+}
+markOop prototype = o->klass()->prototype_header();
+if (!prototype->has_bias_pattern()) {
+// This object has a stale bias from before the handshake
+// was requested. If we fail this race, the object's bias
+// has been revoked by another thread so we simply return.
+markOop biased_value = mark;
+mark = o->cas_set_mark(markOopDesc::prototype()->set_age(mark->age()), mark);
+assert(!o->mark()->has_bias_pattern(), "even if we raced, should still be revoked");
+if (biased_value == mark) {
+_status_code = BiasedLocking::BIAS_REVOKED;
+}
+return;
+}
+if (_biased_locker == mark->biased_locker()) {
+if (mark->bias_epoch() == prototype->bias_epoch()) {
+// Epoch is still valid. This means biaser could be currently
+// synchronized on this object. We must walk its stack looking
+// for monitor records associated with this object and change
+// them to be stack locks if any are found.
+ResourceMark rm;
+BiasedLocking::walk_stack_and_revoke(o, _biased_locker);
+_biased_locker->set_cached_monitor_info(NULL);
+assert(!o->mark()->has_bias_pattern(), "invariant");
+_biased_locker_id = JFR_THREAD_ID(_biased_locker);
+_status_code = BiasedLocking::BIAS_REVOKED;
+return;
+} else {
+markOop biased_value = mark;
+mark = o->cas_set_mark(markOopDesc::prototype()->set_age(mark->age()), mark);
+if (mark == biased_value || !mark->has_bias_pattern()) {
+assert(!o->mark()->has_bias_pattern(), "should be revoked");
+_status_code = (biased_value == mark) ? BiasedLocking::BIAS_REVOKED : BiasedLocking::NOT_BIASED;
+return;
+}
+}
+}
+_status_code = BiasedLocking::NOT_REVOKED;
+}
+BiasedLocking::Condition status_code() const {
+return _status_code;
+}
+traceid biased_locker() const {
+return _biased_locker_id;
+}
+};
 static void post_self_revocation_event(EventBiasedLockSelfRevocation* event, Klass* k) {
 assert(event != NULL, "invariant");
 assert(k != NULL, "invariant");
 assert(event->should_commit(), "invariant");
 event->set_lockClass(k);
 event->commit();
 }
-static void post_revocation_event(EventBiasedLockRevocation* event, Klass* k, VM_RevokeBias* op) {
+static void post_revocation_event(EventBiasedLockRevocation* event, Klass* k, RevokeOneBias* op) {
 assert(event != NULL, "invariant");
 assert(k != NULL, "invariant");
 assert(op != NULL, "invariant");
 assert(event->should_commit(), "invariant");
 event->set_lockClass(k);
-event->set_safepointId(op->safepoint_id());
+event->set_safepointId(0);
 event->set_previousOwner(op->biased_locker());
 event->commit();
 }
 static void post_class_revocation_event(EventBiasedLockClassRevocation* event, Klass* k, VM_BulkRevokeBias* op) {
 event->set_disableBiasing(!op->is_bulk_rebias());
 event->set_safepointId(op->safepoint_id());
 event->commit();
 }
+BiasedLocking::Condition BiasedLocking::single_revoke_with_handshake(Handle obj, JavaThread *requester, JavaThread *biaser) {
+EventBiasedLockRevocation event;
+if (PrintBiasedLockingStatistics) {
+Atomic::inc(handshakes_count_addr());
+}
+log_info(biasedlocking, handshake)("JavaThread " INTPTR_FORMAT " handshaking JavaThread "
+INTPTR_FORMAT " to revoke object " INTPTR_FORMAT, p2i(requester),
+p2i(biaser), p2i(obj()));
+RevokeOneBias revoke(obj, requester, biaser);
+bool executed = Handshake::execute(&revoke, biaser);
+if (revoke.status_code() == NOT_REVOKED) {
+return NOT_REVOKED;
+}
+if (executed) {
+log_info(biasedlocking, handshake)("Handshake revocation for object " INTPTR_FORMAT " succeeded. Bias was %srevoked",
+p2i(obj()), (revoke.status_code() == BIAS_REVOKED ? "" : "already "));
+if (event.should_commit() && revoke.status_code() == BIAS_REVOKED) {
+post_revocation_event(&event, obj->klass(), &revoke);
+}
+assert(!obj->mark()->has_bias_pattern(), "invariant");
+return revoke.status_code();
+} else {
+// Thread was not alive.
+// Grab Threads_lock before manually trying to revoke bias. This avoids race with a newly
+// created JavaThread (that happens to get the same memory address as biaser) synchronizing
+// on this object.
+{
+MutexLocker ml(Threads_lock);
+markOop mark = obj->mark();
+// Check if somebody else was able to revoke it before biased thread exited.
+if (!mark->has_bias_pattern()) {
+return NOT_BIASED;
+}
+ThreadsListHandle tlh;
+markOop prototype = obj->klass()->prototype_header();
+if (!prototype->has_bias_pattern() || (!tlh.includes(biaser) && biaser == mark->biased_locker() &&
+prototype->bias_epoch() == mark->bias_epoch())) {
+obj->cas_set_mark(markOopDesc::prototype()->set_age(mark->age()), mark);
+if (event.should_commit()) {
+post_revocation_event(&event, obj->klass(), &revoke);
+}
+assert(!obj->mark()->has_bias_pattern(), "bias should be revoked by now");
+return BIAS_REVOKED;
+}
+}
+}
+return NOT_REVOKED;
+}
+// Caller should have instantiated a ResourceMark object before calling this method
+void BiasedLocking::walk_stack_and_revoke(oop obj, JavaThread* biased_locker) {
+assert(!SafepointSynchronize::is_at_safepoint() || !ThreadLocalHandshakes,
+"if ThreadLocalHandshakes is enabled this should always be executed outside safepoints");
+assert(Thread::current() == biased_locker || Thread::current()->is_VM_thread(), "wrong thread");
+markOop mark = obj->mark();
+assert(mark->biased_locker() == biased_locker &&
+obj->klass()->prototype_header()->bias_epoch() == mark->bias_epoch(), "invariant");
+log_trace(biasedlocking)("%s(" INTPTR_FORMAT ") revoking object " INTPTR_FORMAT ", mark "
+INTPTR_FORMAT ", type %s, prototype header " INTPTR_FORMAT
+", biaser " INTPTR_FORMAT " %s",
+Thread::current()->is_VM_thread() ? "VMThread" : "JavaThread",
+p2i(Thread::current()),
+p2i(obj),
+p2i(mark),
+obj->klass()->external_name(),
+p2i(obj->klass()->prototype_header()),
+p2i(biased_locker),
+Thread::current()->is_VM_thread() ? "" : "(walking own stack)");
+markOop unbiased_prototype = markOopDesc::prototype()->set_age(obj->mark()->age());
+GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_locker);
+BasicLock* highest_lock = NULL;
+for (int i = 0; i < cached_monitor_info->length(); i++) {
+MonitorInfo* mon_info = cached_monitor_info->at(i);
+if (oopDesc::equals(mon_info->owner(), obj)) {
+log_trace(biasedlocking)("   mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")",
+p2i(mon_info->owner()),
+p2i(obj));
+// Assume recursive case and fix up highest lock below
+markOop mark = markOopDesc::encode((BasicLock*) NULL);
+highest_lock = mon_info->lock();
+highest_lock->set_displaced_header(mark);
+} else {
+log_trace(biasedlocking)("   mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")",
+p2i(mon_info->owner()),
+p2i(obj));
+}
+}
+if (highest_lock != NULL) {
+// Fix up highest lock to contain displaced header and point
+// object at it
+highest_lock->set_displaced_header(unbiased_prototype);
+// Reset object header to point to displaced mark.
+// Must release store the lock address for platforms without TSO
+// ordering (e.g. ppc).
+obj->release_set_mark(markOopDesc::encode(highest_lock));
+assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit");
+log_info(biasedlocking)("  Revoked bias of currently-locked object");
+} else {
+log_info(biasedlocking)("  Revoked bias of currently-unlocked object");
+// Store the unlocked value into the object's header.
+obj->set_mark(unbiased_prototype);
+}
+assert(!obj->mark()->has_bias_pattern(), "must not be biased");
+}
 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) {
 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
-// We can revoke the biases of anonymously-biased objects
+while (true) {
-// efficiently enough that we should not cause these revocations to
+// We can revoke the biases of anonymously-biased objects
-// update the heuristics because doing so may cause unwanted bulk
+// efficiently enough that we should not cause these revocations to
-// revocations (which are expensive) to occur.
+// update the heuristics because doing so may cause unwanted bulk
-markOop mark = obj->mark();
+// revocations (which are expensive) to occur.
-if (mark->is_biased_anonymously() && !attempt_rebias) {
+markOop mark = obj->mark();
-// We are probably trying to revoke the bias of this object due to
+if (mark->is_biased_anonymously() && !attempt_rebias) {
-// an identity hash code computation. Try to revoke the bias
+// We are probably trying to revoke the bias of this object due to
-// without a safepoint. This is possible if we can successfully
+// an identity hash code computation. Try to revoke the bias
-// compare-and-exchange an unbiased header into the mark word of
+// without a safepoint. This is possible if we can successfully
-// the object, meaning that no other thread has raced to acquire
+// compare-and-exchange an unbiased header into the mark word of
-// the bias of the object.
+// the object, meaning that no other thread has raced to acquire
-markOop biased_value       = mark;
+// the bias of the object.
-markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
-markOop res_mark = obj->cas_set_mark(unbiased_prototype, mark);
-if (res_mark == biased_value) {
-return BIAS_REVOKED;
-}
-} else if (mark->has_bias_pattern()) {
-Klass* k = obj->klass();
-markOop prototype_header = k->prototype_header();
-if (!prototype_header->has_bias_pattern()) {
-// This object has a stale bias from before the bulk revocation
-// for this data type occurred. It's pointless to update the
-// heuristics at this point so simply update the header with a
-// CAS. If we fail this race, the object's bias has been revoked
-// by another thread so we simply return and let the caller deal
-// with it.
 markOop biased_value       = mark;
-markOop res_mark = obj->cas_set_mark(prototype_header, mark);
+markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
-assert(!obj->mark()->has_bias_pattern(), "even if we raced, should still be revoked");
+markOop res_mark = obj->cas_set_mark(unbiased_prototype, mark);
-return BIAS_REVOKED;
+if (res_mark == biased_value) {
-} else if (prototype_header->bias_epoch() != mark->bias_epoch()) {
+return BIAS_REVOKED;
-// The epoch of this biasing has expired indicating that the
+}
-// object is effectively unbiased. Depending on whether we need
+mark = res_mark;  // Refresh mark with the latest value.
-// to rebias or revoke the bias of this object we can do it
+} else if (mark->has_bias_pattern()) {
-// efficiently enough with a CAS that we shouldn't update the
+Klass* k = obj->klass();
-// heuristics. This is normally done in the assembly code but we
+markOop prototype_header = k->prototype_header();
-// can reach this point due to various points in the runtime
+if (!prototype_header->has_bias_pattern()) {
-// needing to revoke biases.
+// This object has a stale bias from before the bulk revocation
-if (attempt_rebias) {
+// for this data type occurred. It's pointless to update the
-assert(THREAD->is_Java_thread(), "");
+// heuristics at this point so simply update the header with a
-markOop biased_value       = mark;
+// CAS. If we fail this race, the object's bias has been revoked
-markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch());
+// by another thread so we simply return and let the caller deal
-markOop res_mark = obj->cas_set_mark(rebiased_prototype, mark);
+// with it.
-if (res_mark == biased_value) {
+obj->cas_set_mark(prototype_header->set_age(mark->age()), mark);
-return BIAS_REVOKED_AND_REBIASED;
+assert(!obj->mark()->has_bias_pattern(), "even if we raced, should still be revoked");
+return BIAS_REVOKED;
+} else if (prototype_header->bias_epoch() != mark->bias_epoch()) {
+// The epoch of this biasing has expired indicating that the
+// object is effectively unbiased. Depending on whether we need
+// to rebias or revoke the bias of this object we can do it
+// efficiently enough with a CAS that we shouldn't update the
+// heuristics. This is normally done in the assembly code but we
+// can reach this point due to various points in the runtime
+// needing to revoke biases.
+markOop res_mark;
+if (attempt_rebias) {
+assert(THREAD->is_Java_thread(), "");
+markOop biased_value       = mark;
+markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch());
+res_mark = obj->cas_set_mark(rebiased_prototype, mark);
+if (res_mark == biased_value) {
+return BIAS_REVOKED_AND_REBIASED;
+}
+} else {
+markOop biased_value       = mark;
+markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
+res_mark = obj->cas_set_mark(unbiased_prototype, mark);
+if (res_mark == biased_value) {
+return BIAS_REVOKED;
+}
 }
+mark = res_mark;  // Refresh mark with the latest value.
+}
+}
+HeuristicsResult heuristics = update_heuristics(obj());
+if (heuristics == HR_NOT_BIASED) {
+return NOT_BIASED;
+} else if (heuristics == HR_SINGLE_REVOKE) {
+JavaThread *blt = mark->biased_locker();
+assert(blt != NULL, "invariant");
+if (blt == THREAD) {
+// A thread is trying to revoke the bias of an object biased
+// toward it, again likely due to an identity hash code
+// computation. We can again avoid a safepoint/handshake in this case
+// since we are only going to walk our own stack. There are no
+// races with revocations occurring in other threads because we
+// reach no safepoints in the revocation path.
+EventBiasedLockSelfRevocation event;
+ResourceMark rm;
+walk_stack_and_revoke(obj(), blt);
+blt->set_cached_monitor_info(NULL);
+assert(!obj->mark()->has_bias_pattern(), "invariant");
+if (event.should_commit()) {
+post_self_revocation_event(&event, obj->klass());
+}
+return BIAS_REVOKED;
 } else {
-markOop biased_value       = mark;
+BiasedLocking::Condition cond = single_revoke_with_handshake(obj, (JavaThread*)THREAD, blt);
-markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
+if (cond != NOT_REVOKED) {
-markOop res_mark = obj->cas_set_mark(unbiased_prototype, mark);
+return cond;
-if (res_mark == biased_value) {
-return BIAS_REVOKED;
 }
 }
-}
+} else {
-}
+assert((heuristics == HR_BULK_REVOKE) ||
+(heuristics == HR_BULK_REBIAS), "?");
-HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias);
+EventBiasedLockClassRevocation event;
-if (heuristics == HR_NOT_BIASED) {
+VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*)THREAD,
-return NOT_BIASED;
+(heuristics == HR_BULK_REBIAS),
-} else if (heuristics == HR_SINGLE_REVOKE) {
+attempt_rebias);
-Klass *k = obj->klass();
+VMThread::execute(&bulk_revoke);
-markOop prototype_header = k->prototype_header();
-if (mark->biased_locker() == THREAD &&
-prototype_header->bias_epoch() == mark->bias_epoch()) {
-// A thread is trying to revoke the bias of an object biased
-// toward it, again likely due to an identity hash code
-// computation. We can again avoid a safepoint in this case
-// since we are only going to walk our own stack. There are no
-// races with revocations occurring in other threads because we
-// reach no safepoints in the revocation path.
-// Also check the epoch because even if threads match, another thread
-// can come in with a CAS to steal the bias of an object that has a
-// stale epoch.
-ResourceMark rm;
-log_info(biasedlocking)("Revoking bias by walking my own stack:");
-EventBiasedLockSelfRevocation event;
-BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD, NULL);
-((JavaThread*) THREAD)->set_cached_monitor_info(NULL);
-assert(cond == BIAS_REVOKED, "why not?");
 if (event.should_commit()) {
-post_self_revocation_event(&event, k);
+post_class_revocation_event(&event, obj->klass(), &bulk_revoke);
 }
-return cond;
+return bulk_revoke.status_code();
-} else {
+}
-EventBiasedLockRevocation event;
+}
-VM_RevokeBias revoke(&obj, (JavaThread*) THREAD);
+}
-VMThread::execute(&revoke);
-if (event.should_commit() && revoke.status_code() != NOT_BIASED) {
+// All objects in objs should be locked by biaser
-post_revocation_event(&event, k, &revoke);
+void BiasedLocking::revoke(GrowableArray<Handle>* objs, JavaThread *biaser) {
-}
+bool clean_my_cache = false;
-return revoke.status_code();
+for (int i = 0; i < objs->length(); i++) {
-}
+oop obj = (objs->at(i))();
-}
+markOop mark = obj->mark();
+if (mark->has_bias_pattern()) {
-assert((heuristics == HR_BULK_REVOKE) ||
+walk_stack_and_revoke(obj, biaser);
-(heuristics == HR_BULK_REBIAS), "?");
+clean_my_cache = true;
-EventBiasedLockClassRevocation event;
+}
-VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD,
+}
-(heuristics == HR_BULK_REBIAS),
+if (clean_my_cache) {
-attempt_rebias);
+clean_up_cached_monitor_info(biaser);
-VMThread::execute(&bulk_revoke);
+}
-if (event.should_commit()) {
-post_class_revocation_event(&event, obj->klass(), &bulk_revoke);
-}
-return bulk_revoke.status_code();
-}
-void BiasedLocking::revoke(GrowableArray<Handle>* objs) {
-assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
-if (objs->length() == 0) {
-return;
-}
-VM_RevokeBias revoke(objs, JavaThread::current());
-VMThread::execute(&revoke);
 }
 void BiasedLocking::revoke_at_safepoint(Handle h_obj) {
 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
 oop obj = h_obj();
-HeuristicsResult heuristics = update_heuristics(obj, false);
+HeuristicsResult heuristics = update_heuristics(obj);
 if (heuristics == HR_SINGLE_REVOKE) {
-revoke_bias(obj, false, false, NULL, NULL);
+JavaThread* biased_locker = NULL;
+single_revoke_at_safepoint(obj, false, false, NULL, &biased_locker);
+if (biased_locker) {
+clean_up_cached_monitor_info(biased_locker);
+}
 } else if ((heuristics == HR_BULK_REBIAS) ||
 (heuristics == HR_BULK_REVOKE)) {
 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
-}
+clean_up_cached_monitor_info();
-clean_up_cached_monitor_info();
+}
 }
 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) {
 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
 int len = objs->length();
 for (int i = 0; i < len; i++) {
 oop obj = (objs->at(i))();
-HeuristicsResult heuristics = update_heuristics(obj, false);
+HeuristicsResult heuristics = update_heuristics(obj);
 if (heuristics == HR_SINGLE_REVOKE) {
-revoke_bias(obj, false, false, NULL, NULL);
+single_revoke_at_safepoint(obj, false, false, NULL, NULL);
 } else if ((heuristics == HR_BULK_REBIAS) ||
 (heuristics == HR_BULK_REVOKE)) {
 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
 }
 }
 int* BiasedLocking::total_entry_count_addr()                   { return _counters.total_entry_count_addr(); }
 int* BiasedLocking::biased_lock_entry_count_addr()             { return _counters.biased_lock_entry_count_addr(); }
 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); }
 int* BiasedLocking::rebiased_lock_entry_count_addr()           { return _counters.rebiased_lock_entry_count_addr(); }
 int* BiasedLocking::revoked_lock_entry_count_addr()            { return _counters.revoked_lock_entry_count_addr(); }
+int* BiasedLocking::handshakes_count_addr()                    { return _counters.handshakes_count_addr(); }
 int* BiasedLocking::fast_path_entry_count_addr()               { return _counters.fast_path_entry_count_addr(); }
 int* BiasedLocking::slow_path_entry_count_addr()               { return _counters.slow_path_entry_count_addr(); }
 // BiasedLockingCounters
 tty->print_cr("# total entries: %d", _total_entry_count);
 tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count);
 tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count);
 tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count);
 tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count);
+tty->print_cr("# handshakes entries: %d", _handshakes_count);
 tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count);
 tty->print_cr("# slow path lock entries: %d", slow_path_entry_count());
 }
 void BiasedLockingCounters::print() const { print_on(tty); }

changeset 55625	f7e8dbb77156
parent 55537	4309fedaf7dc
child 57777	90ead0febf56