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src/hotspot/share/runtime/biasedLocking.cpp
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*** 117,126 ****
--- 117,127 ----
// 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;
*** 151,163 ****
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) {
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
--- 152,168 ----
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).
! 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
*** 166,176 ****
" because it's no longer biased)",
p2i((void *)obj), (intptr_t) mark,
obj->klass()->external_name(),
(intptr_t) requesting_thread);
}
! return BiasedLocking::NOT_BIASED;
}
uint age = mark->age();
markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age);
markOop unbiased_prototype = markOopDesc::prototype()->set_age(age);
--- 171,181 ----
" because it's no longer biased)",
p2i((void *)obj), (intptr_t) mark,
obj->klass()->external_name(),
(intptr_t) requesting_thread);
}
! 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);
*** 212,222 ****
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;
}
// Handle case where the thread toward which the object was biased has exited
bool thread_is_alive = false;
if (requesting_thread == biased_thread) {
--- 217,227 ----
if (!is_bulk) {
log_info(biasedlocking)(" Revoked bias of anonymously-biased object");
} else {
log_trace(biasedlocking)(" Revoked bias of anonymously-biased object");
}
! 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) {
*** 237,247 ****
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;
}
// Log at "info" level if not bulk, else "trace" level
if (!is_bulk) {
log_info(biasedlocking)(" Revoked bias of object biased toward live thread ("
--- 242,252 ----
PTR_FORMAT ")", p2i(biased_thread));
} else {
log_trace(biasedlocking)(" Revoked bias of object biased toward dead thread ("
PTR_FORMAT ")", p2i(biased_thread));
}
! 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 ("
*** 262,272 ****
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
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 ")",
--- 267,277 ----
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 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 ")",
*** 277,287 ****
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
// 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) {
--- 282,292 ----
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 at "info" level if not bulk, else "trace" level
if (!is_bulk) {
*** 307,317 ****
// If requested, return information on which thread held the bias
if (biased_locker != NULL) {
*biased_locker = biased_thread;
}
! return BiasedLocking::BIAS_REVOKED;
}
enum HeuristicsResult {
HR_NOT_BIASED = 1,
--- 312,322 ----
// If requested, return information on which thread held the bias
if (biased_locker != NULL) {
*biased_locker = biased_thread;
}
! return BIAS_REVOKED;
}
enum HeuristicsResult {
HR_NOT_BIASED = 1,
*** 319,329 ****
HR_BULK_REBIAS = 3,
HR_BULK_REVOKE = 4
};
! static HeuristicsResult update_heuristics(oop o, bool allow_rebias) {
markOop mark = o->mark();
if (!mark->has_bias_pattern()) {
return HR_NOT_BIASED;
}
--- 324,334 ----
HR_BULK_REBIAS = 3,
HR_BULK_REVOKE = 4
};
! static HeuristicsResult update_heuristics(oop o) {
markOop mark = o->mark();
if (!mark->has_bias_pattern()) {
return HR_NOT_BIASED;
}
*** 372,386 ****
return HR_SINGLE_REVOKE;
}
! static BiasedLocking::Condition 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");
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),
--- 377,392 ----
return HR_SINGLE_REVOKE;
}
! 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),
*** 388,398 ****
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;
{
JavaThreadIteratorWithHandle jtiwh;
--- 394,403 ----
*** 430,440 ****
}
}
// 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);
} else {
if (log_is_enabled(Info, biasedlocking)) {
ResourceMark rm;
log_info(biasedlocking)("* Disabling biased locking for type %s", klass->external_name());
}
--- 435,445 ----
}
}
// At this point we're done. All we have to do is potentially
// adjust the header of the given object to revoke its bias.
! 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());
}
*** 452,483 ****
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);
}
}
}
// 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);
}
} // ThreadsListHandle is destroyed here.
log_info(biasedlocking)("* Ending bulk revocation");
! BiasedLocking::Condition status_code = BiasedLocking::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;
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)),
--- 457,488 ----
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()) {
! 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
! single_revoke_at_safepoint(o, false, true, requesting_thread, NULL);
}
} // ThreadsListHandle is destroyed here.
log_info(biasedlocking)("* Ending bulk revocation");
! 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 = 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)),
*** 485,623 ****
return status_code;
}
! static void clean_up_cached_monitor_info() {
// 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:
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;
public:
! VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread,
! bool bulk_rebias,
! bool attempt_rebias_of_object)
! : VM_RevokeBias(obj, requesting_thread)
! , _bulk_rebias(bulk_rebias)
! , _attempt_rebias_of_object(attempt_rebias_of_object) {}
! 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);
! _safepoint_id = SafepointSynchronize::safepoint_id();
! clean_up_cached_monitor_info();
}
! bool is_bulk_rebias() const {
! return _bulk_rebias;
}
};
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) {
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_previousOwner(op->biased_locker());
event->commit();
}
static void post_class_revocation_event(EventBiasedLockClassRevocation* event, Klass* k, VM_BulkRevokeBias* op) {
--- 490,645 ----
return status_code;
}
! static void clean_up_cached_monitor_info(JavaThread* thread = NULL) {
! if (thread != NULL) {
! thread->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_BulkRevokeBias : public VM_Operation {
! private:
Handle* _obj;
JavaThread* _requesting_thread;
+ 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)
: _obj(obj)
, _requesting_thread(requesting_thread)
+ , _bulk_rebias(bulk_rebias)
+ , _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 void doit() {
! _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, 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(0);
event->set_previousOwner(op->biased_locker());
event->commit();
}
static void post_class_revocation_event(EventBiasedLockClassRevocation* event, Klass* k, VM_BulkRevokeBias* op) {
*** 629,641 ****
--- 651,780 ----
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");
+ while (true) {
// We can revoke the biases of anonymously-biased objects
// efficiently enough that we should not cause these revocations to
// update the heuristics because doing so may cause unwanted bulk
// revocations (which are expensive) to occur.
markOop mark = obj->mark();
*** 650,784 ****
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);
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.
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());
! markOop 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());
! markOop res_mark = obj->cas_set_mark(unbiased_prototype, mark);
if (res_mark == biased_value) {
return BIAS_REVOKED;
}
}
}
}
! HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias);
if (heuristics == HR_NOT_BIASED) {
return NOT_BIASED;
} else if (heuristics == HR_SINGLE_REVOKE) {
! Klass *k = obj->klass();
! 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);
}
! return cond;
} else {
! EventBiasedLockRevocation event;
! VM_RevokeBias revoke(&obj, (JavaThread*) THREAD);
! VMThread::execute(&revoke);
! if (event.should_commit() && revoke.status_code() != NOT_BIASED) {
! post_revocation_event(&event, k, &revoke);
! }
! return revoke.status_code();
}
}
!
assert((heuristics == HR_BULK_REVOKE) ||
(heuristics == HR_BULK_REBIAS), "?");
EventBiasedLockClassRevocation event;
! VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD,
(heuristics == HR_BULK_REBIAS),
attempt_rebias);
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);
if (heuristics == HR_SINGLE_REVOKE) {
! revoke_bias(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);
- }
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);
if (heuristics == HR_SINGLE_REVOKE) {
! revoke_bias(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);
}
}
--- 789,928 ----
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;
}
+ mark = res_mark; // Refresh mark with the latest value.
} 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.
! obj->cas_set_mark(prototype_header->set_age(mark->age()), mark);
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 {
! BiasedLocking::Condition cond = single_revoke_with_handshake(obj, (JavaThread*)THREAD, blt);
! if (cond != NOT_REVOKED) {
! return cond;
}
}
! } else {
assert((heuristics == HR_BULK_REVOKE) ||
(heuristics == HR_BULK_REBIAS), "?");
EventBiasedLockClassRevocation event;
! VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*)THREAD,
(heuristics == HR_BULK_REBIAS),
attempt_rebias);
VMThread::execute(&bulk_revoke);
if (event.should_commit()) {
post_class_revocation_event(&event, obj->klass(), &bulk_revoke);
}
return bulk_revoke.status_code();
+ }
+ }
}
! // All objects in objs should be locked by biaser
! void BiasedLocking::revoke(GrowableArray<Handle>* objs, JavaThread *biaser) {
! bool clean_my_cache = false;
! for (int i = 0; i < objs->length(); i++) {
! oop obj = (objs->at(i))();
! markOop mark = obj->mark();
! if (mark->has_bias_pattern()) {
! walk_stack_and_revoke(obj, biaser);
! clean_my_cache = true;
! }
! }
! if (clean_my_cache) {
! clean_up_cached_monitor_info(biaser);
}
}
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);
if (heuristics == HR_SINGLE_REVOKE) {
! 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();
+ }
}
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);
if (heuristics == HR_SINGLE_REVOKE) {
! 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);
}
}
*** 860,869 ****
--- 1004,1014 ----
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
*** 883,892 ****
--- 1028,1038 ----
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); }
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