--- a/hotspot/src/share/vm/oops/constantPool.cpp Wed Jun 18 14:21:28 2014 -0700
+++ b/hotspot/src/share/vm/oops/constantPool.cpp Thu Jun 19 11:16:10 2014 -0400
@@ -71,7 +71,6 @@
// only set to non-zero if constant pool is merged by RedefineClasses
set_version(0);
- set_lock(new Monitor(Monitor::nonleaf + 2, "A constant pool lock"));
// initialize tag array
int length = tags->length();
@@ -100,9 +99,6 @@
void ConstantPool::release_C_heap_structures() {
// walk constant pool and decrement symbol reference counts
unreference_symbols();
-
- delete _lock;
- set_lock(NULL);
}
objArrayOop ConstantPool::resolved_references() const {
@@ -146,8 +142,7 @@
// CDS support. Create a new resolved_references array.
void ConstantPool::restore_unshareable_info(TRAPS) {
- // Only create the new resolved references array and lock if it hasn't been
- // attempted before
+ // Only create the new resolved references array if it hasn't been attempted before
if (resolved_references() != NULL) return;
// restore the C++ vtable from the shared archive
@@ -163,9 +158,6 @@
ClassLoaderData* loader_data = pool_holder()->class_loader_data();
set_resolved_references(loader_data->add_handle(refs_handle));
}
-
- // Also need to recreate the mutex. Make sure this matches the constructor
- set_lock(new Monitor(Monitor::nonleaf + 2, "A constant pool lock"));
}
}
@@ -176,7 +168,6 @@
set_resolved_reference_length(
resolved_references() != NULL ? resolved_references()->length() : 0);
set_resolved_references(NULL);
- set_lock(NULL);
}
int ConstantPool::cp_to_object_index(int cp_index) {
@@ -186,11 +177,41 @@
return (i < 0) ? _no_index_sentinel : i;
}
+void ConstantPool::trace_class_resolution(constantPoolHandle this_cp, KlassHandle k) {
+ ResourceMark rm;
+ int line_number = -1;
+ const char * source_file = NULL;
+ if (JavaThread::current()->has_last_Java_frame()) {
+ // try to identify the method which called this function.
+ vframeStream vfst(JavaThread::current());
+ if (!vfst.at_end()) {
+ line_number = vfst.method()->line_number_from_bci(vfst.bci());
+ Symbol* s = vfst.method()->method_holder()->source_file_name();
+ if (s != NULL) {
+ source_file = s->as_C_string();
+ }
+ }
+ }
+ if (k() != this_cp->pool_holder()) {
+ // only print something if the classes are different
+ if (source_file != NULL) {
+ tty->print("RESOLVE %s %s %s:%d\n",
+ this_cp->pool_holder()->external_name(),
+ InstanceKlass::cast(k())->external_name(), source_file, line_number);
+ } else {
+ tty->print("RESOLVE %s %s\n",
+ this_cp->pool_holder()->external_name(),
+ InstanceKlass::cast(k())->external_name());
+ }
+ }
+}
+
Klass* ConstantPool::klass_at_impl(constantPoolHandle this_cp, int which, TRAPS) {
+ assert(THREAD->is_Java_thread(), "must be a Java thread");
+
// A resolved constantPool entry will contain a Klass*, otherwise a Symbol*.
- // It is not safe to rely on the tag bit's here, since we don't have a lock, and the entry and
- // tag is not updated atomicly.
-
+ // It is not safe to rely on the tag bit's here, since we don't have a lock, and
+ // the entry and tag is not updated atomicly.
CPSlot entry = this_cp->slot_at(which);
if (entry.is_resolved()) {
assert(entry.get_klass()->is_klass(), "must be");
@@ -198,115 +219,51 @@
return entry.get_klass();
}
- // Acquire lock on constant oop while doing update. After we get the lock, we check if another object
- // already has updated the object
- assert(THREAD->is_Java_thread(), "must be a Java thread");
- bool do_resolve = false;
- bool in_error = false;
-
- // Create a handle for the mirror. This will preserve the resolved class
- // until the loader_data is registered.
- Handle mirror_handle;
-
- Symbol* name = NULL;
- Handle loader;
- { MonitorLockerEx ml(this_cp->lock());
-
- if (this_cp->tag_at(which).is_unresolved_klass()) {
- if (this_cp->tag_at(which).is_unresolved_klass_in_error()) {
- in_error = true;
- } else {
- do_resolve = true;
- name = this_cp->unresolved_klass_at(which);
- loader = Handle(THREAD, this_cp->pool_holder()->class_loader());
- }
- }
- } // unlocking constantPool
-
-
- // The original attempt to resolve this constant pool entry failed so find the
- // class of the original error and throw another error of the same class (JVMS 5.4.3).
- // If there is a detail message, pass that detail message to the error constructor.
- // The JVMS does not strictly require us to duplicate the same detail message,
- // or any internal exception fields such as cause or stacktrace. But since the
- // detail message is often a class name or other literal string, we will repeat it if
- // we can find it in the symbol table.
- if (in_error) {
+ // This tag doesn't change back to unresolved class unless at a safepoint.
+ if (this_cp->tag_at(which).is_unresolved_klass_in_error()) {
+ // The original attempt to resolve this constant pool entry failed so find the
+ // class of the original error and throw another error of the same class
+ // (JVMS 5.4.3).
+ // If there is a detail message, pass that detail message to the error.
+ // The JVMS does not strictly require us to duplicate the same detail message,
+ // or any internal exception fields such as cause or stacktrace. But since the
+ // detail message is often a class name or other literal string, we will repeat it
+ // if we can find it in the symbol table.
throw_resolution_error(this_cp, which, CHECK_0);
+ ShouldNotReachHere();
}
- if (do_resolve) {
- // this_cp must be unlocked during resolve_or_fail
- oop protection_domain = this_cp->pool_holder()->protection_domain();
- Handle h_prot (THREAD, protection_domain);
- Klass* kk = SystemDictionary::resolve_or_fail(name, loader, h_prot, true, THREAD);
- KlassHandle k;
- if (!HAS_PENDING_EXCEPTION) {
- k = KlassHandle(THREAD, kk);
- // preserve the resolved klass.
- mirror_handle = Handle(THREAD, kk->java_mirror());
- // Do access check for klasses
- verify_constant_pool_resolve(this_cp, k, THREAD);
- }
-
- // Failed to resolve class. We must record the errors so that subsequent attempts
- // to resolve this constant pool entry fail with the same error (JVMS 5.4.3).
- if (HAS_PENDING_EXCEPTION) {
- MonitorLockerEx ml(this_cp->lock());
-
- // some other thread has beaten us and has resolved the class.
- if (this_cp->tag_at(which).is_klass()) {
- CLEAR_PENDING_EXCEPTION;
- entry = this_cp->resolved_klass_at(which);
- return entry.get_klass();
- }
+ Handle mirror_handle;
+ Symbol* name = entry.get_symbol();
+ Handle loader (THREAD, this_cp->pool_holder()->class_loader());
+ Handle protection_domain (THREAD, this_cp->pool_holder()->protection_domain());
+ Klass* kk = SystemDictionary::resolve_or_fail(name, loader, protection_domain, true, THREAD);
+ KlassHandle k (THREAD, kk);
+ if (!HAS_PENDING_EXCEPTION) {
+ // preserve the resolved klass from unloading
+ mirror_handle = Handle(THREAD, kk->java_mirror());
+ // Do access check for klasses
+ verify_constant_pool_resolve(this_cp, k, THREAD);
+ }
- // The tag could have changed to in-error before the lock but we have to
- // handle that here for the class case.
- save_and_throw_exception(this_cp, which, constantTag(JVM_CONSTANT_UnresolvedClass), CHECK_0);
- }
+ // Failed to resolve class. We must record the errors so that subsequent attempts
+ // to resolve this constant pool entry fail with the same error (JVMS 5.4.3).
+ if (HAS_PENDING_EXCEPTION) {
+ save_and_throw_exception(this_cp, which, constantTag(JVM_CONSTANT_UnresolvedClass), CHECK_0);
+ }
- if (TraceClassResolution && !k()->oop_is_array()) {
- // skip resolving the constant pool so that this code get's
- // called the next time some bytecodes refer to this class.
- ResourceMark rm;
- int line_number = -1;
- const char * source_file = NULL;
- if (JavaThread::current()->has_last_Java_frame()) {
- // try to identify the method which called this function.
- vframeStream vfst(JavaThread::current());
- if (!vfst.at_end()) {
- line_number = vfst.method()->line_number_from_bci(vfst.bci());
- Symbol* s = vfst.method()->method_holder()->source_file_name();
- if (s != NULL) {
- source_file = s->as_C_string();
- }
- }
- }
- if (k() != this_cp->pool_holder()) {
- // only print something if the classes are different
- if (source_file != NULL) {
- tty->print("RESOLVE %s %s %s:%d\n",
- this_cp->pool_holder()->external_name(),
- InstanceKlass::cast(k())->external_name(), source_file, line_number);
- } else {
- tty->print("RESOLVE %s %s\n",
- this_cp->pool_holder()->external_name(),
- InstanceKlass::cast(k())->external_name());
- }
- }
+ // Make this class loader depend upon the class loader owning the class reference
+ ClassLoaderData* this_key = this_cp->pool_holder()->class_loader_data();
+ this_key->record_dependency(k(), CHECK_NULL); // Can throw OOM
+
+ if (TraceClassResolution && !k->oop_is_array()) {
+ // skip resolving the constant pool so that this code gets
+ // called the next time some bytecodes refer to this class.
+ trace_class_resolution(this_cp, k);
return k();
} else {
- MonitorLockerEx ml(this_cp->lock());
- // Only updated constant pool - if it is resolved.
- do_resolve = this_cp->tag_at(which).is_unresolved_klass();
- if (do_resolve) {
- ClassLoaderData* this_key = this_cp->pool_holder()->class_loader_data();
- this_key->record_dependency(k(), CHECK_NULL); // Can throw OOM
this_cp->klass_at_put(which, k());
}
- }
- }
entry = this_cp->resolved_klass_at(which);
assert(entry.is_resolved() && entry.get_klass()->is_klass(), "must be resolved at this point");
@@ -576,7 +533,7 @@
switch (tag.value()) {
case JVM_CONSTANT_UnresolvedClass:
// return the class name in the error message
- message = this_cp->unresolved_klass_at(which);
+ message = this_cp->klass_name_at(which);
break;
case JVM_CONSTANT_MethodHandle:
// return the method handle name in the error message
@@ -606,7 +563,6 @@
// in the resolution error table, so that the same exception is thrown again.
void ConstantPool::save_and_throw_exception(constantPoolHandle this_cp, int which,
constantTag tag, TRAPS) {
- assert(this_cp->lock()->is_locked(), "constant pool lock should be held");
Symbol* error = PENDING_EXCEPTION->klass()->name();
int error_tag = tag.error_value();
@@ -620,7 +576,14 @@
} else if (this_cp->tag_at(which).value() != error_tag) {
Symbol* message = exception_message(this_cp, which, tag, PENDING_EXCEPTION);
SystemDictionary::add_resolution_error(this_cp, which, error, message);
- this_cp->tag_at_put(which, error_tag);
+ // CAS in the tag. If a thread beat us to registering this error that's fine.
+ // If another thread resolved the reference, this is an error. The resolution
+ // must deterministically get an error. So why do we save this?
+ // We save this because jvmti can add classes to the bootclass path after this
+ // error, so it needs to get the same error if the error is first.
+ jbyte old_tag = Atomic::cmpxchg((jbyte)error_tag,
+ (jbyte*)this_cp->tag_addr_at(which), (jbyte)tag.value());
+ assert(old_tag == error_tag || old_tag == tag.value(), "should not be resolved otherwise");
} else {
// some other thread put this in error state
throw_resolution_error(this_cp, which, CHECK);
@@ -710,7 +673,6 @@
THREAD);
result_oop = value();
if (HAS_PENDING_EXCEPTION) {
- MonitorLockerEx ml(this_cp->lock()); // lock cpool to change tag.
save_and_throw_exception(this_cp, index, tag, CHECK_NULL);
}
break;
@@ -727,7 +689,6 @@
Handle value = SystemDictionary::find_method_handle_type(signature, klass, THREAD);
result_oop = value();
if (HAS_PENDING_EXCEPTION) {
- MonitorLockerEx ml(this_cp->lock()); // lock cpool to change tag.
save_and_throw_exception(this_cp, index, tag, CHECK_NULL);
}
break;
@@ -765,22 +726,17 @@
}
if (cache_index >= 0) {
- // Cache the oop here also.
- Handle result_handle(THREAD, result_oop);
- MonitorLockerEx ml(this_cp->lock()); // don't know if we really need this
- oop result = this_cp->resolved_references()->obj_at(cache_index);
- // Benign race condition: resolved_references may already be filled in while we were trying to lock.
+ // Benign race condition: resolved_references may already be filled in.
// The important thing here is that all threads pick up the same result.
// It doesn't matter which racing thread wins, as long as only one
// result is used by all threads, and all future queries.
- // That result may be either a resolved constant or a failure exception.
- if (result == NULL) {
- this_cp->resolved_references()->obj_at_put(cache_index, result_handle());
- return result_handle();
+ oop old_result = this_cp->resolved_references()->atomic_compare_exchange_oop(cache_index, result_oop, NULL);
+ if (old_result == NULL) {
+ return result_oop; // was installed
} else {
// Return the winning thread's result. This can be different than
- // result_handle() for MethodHandles.
- return result;
+ // the result here for MethodHandles.
+ return old_result;
}
} else {
return result_oop;
@@ -853,9 +809,8 @@
}
-// Iterate over symbols and decrement ones which are Symbol*s.
-// This is done during GC so do not need to lock constantPool unless we
-// have per-thread safepoints.
+// Iterate over symbols and decrement ones which are Symbol*s
+// This is done during GC.
// Only decrement the UTF8 symbols. Unresolved classes and strings point to
// these symbols but didn't increment the reference count.
void ConstantPool::unreference_symbols() {
@@ -987,8 +942,8 @@
case JVM_CONSTANT_UnresolvedClass:
{
- Symbol* k1 = unresolved_klass_at(index1);
- Symbol* k2 = cp2->unresolved_klass_at(index2);
+ Symbol* k1 = klass_name_at(index1);
+ Symbol* k2 = cp2->klass_name_at(index2);
if (k1 == k2) {
return true;
}
@@ -1970,7 +1925,6 @@
break;
case JVM_CONSTANT_UnresolvedClass : // fall-through
case JVM_CONSTANT_UnresolvedClassInError: {
- // unresolved_klass_at requires lock or safe world.
CPSlot entry = slot_at(index);
if (entry.is_resolved()) {
entry.get_klass()->print_value_on(st);