--- a/hotspot/src/share/vm/classfile/classLoaderData.cpp Fri Jun 03 01:31:01 2016 +0000
+++ b/hotspot/src/share/vm/classfile/classLoaderData.cpp Thu Jun 02 23:37:09 2016 -0400
@@ -67,6 +67,7 @@
#include "runtime/javaCalls.hpp"
#include "runtime/jniHandles.hpp"
#include "runtime/mutex.hpp"
+#include "runtime/orderAccess.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/synchronizer.hpp"
#include "utilities/growableArray.hpp"
@@ -76,6 +77,11 @@
#include "trace/tracing.hpp"
#endif
+// helper function to avoid in-line casts
+template <typename T> static T* load_ptr_acquire(T* volatile *p) {
+ return static_cast<T*>(OrderAccess::load_ptr_acquire(p));
+}
+
ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
@@ -147,20 +153,23 @@
}
void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
- for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+ // Lock-free access requires load_ptr_acquire
+ for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
klass_closure->do_klass(k);
assert(k != k->next_link(), "no loops!");
}
}
void ClassLoaderData::classes_do(void f(Klass * const)) {
+ assert_locked_or_safepoint(_metaspace_lock);
for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
f(k);
}
}
void ClassLoaderData::methods_do(void f(Method*)) {
- for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+ // Lock-free access requires load_ptr_acquire
+ for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
if (k->is_instance_klass()) {
InstanceKlass::cast(k)->methods_do(f);
}
@@ -179,7 +188,8 @@
}
void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
- for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+ // Lock-free access requires load_ptr_acquire
+ for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
if (k->is_instance_klass()) {
f(InstanceKlass::cast(k));
}
@@ -188,6 +198,7 @@
}
void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
+ assert_locked_or_safepoint(Module_lock);
if (_modules != NULL) {
for (int i = 0; i < _modules->table_size(); i++) {
for (ModuleEntry* entry = _modules->bucket(i);
@@ -200,9 +211,11 @@
}
void ClassLoaderData::packages_do(void f(PackageEntry*)) {
- if (_packages != NULL) {
- for (int i = 0; i < _packages->table_size(); i++) {
- for (PackageEntry* entry = _packages->bucket(i);
+ // Lock-free access requires load_ptr_acquire
+ PackageEntryTable* packages = load_ptr_acquire(&_packages);
+ if (packages != NULL) {
+ for (int i = 0; i < packages->table_size(); i++) {
+ for (PackageEntry* entry = packages->bucket(i);
entry != NULL;
entry = entry->next()) {
f(entry);
@@ -325,10 +338,9 @@
MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
Klass* old_value = _klasses;
k->set_next_link(old_value);
- // Make sure linked class is stable, since the class list is walked without a lock
- OrderAccess::storestore();
- // link the new item into the list
- _klasses = k;
+ // Link the new item into the list, making sure the linked class is stable
+ // since the list can be walked without a lock
+ OrderAccess::release_store_ptr(&_klasses, k);
}
if (publicize && k->class_loader_data() != NULL) {
@@ -343,11 +355,10 @@
}
}
-// This is called by InstanceKlass::deallocate_contents() to remove the
-// scratch_class for redefine classes. We need a lock because there it may not
-// be called at a safepoint if there's an error.
+// Remove a klass from the _klasses list for scratch_class during redefinition
+// or parsed class in the case of an error.
void ClassLoaderData::remove_class(Klass* scratch_class) {
- MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
+ assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
Klass* prev = NULL;
for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
if (k == scratch_class) {
@@ -390,42 +401,46 @@
PackageEntryTable* ClassLoaderData::packages() {
// Lazily create the package entry table at first request.
- if (_packages == NULL) {
+ // Lock-free access requires load_ptr_acquire.
+ PackageEntryTable* packages = load_ptr_acquire(&_packages);
+ if (packages == NULL) {
MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
// Check if _packages got allocated while we were waiting for this lock.
- if (_packages == NULL) {
- _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
+ if ((packages = _packages) == NULL) {
+ packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
+ // Ensure _packages is stable, since it is examined without a lock
+ OrderAccess::release_store_ptr(&_packages, packages);
}
}
- return _packages;
+ return packages;
}
ModuleEntryTable* ClassLoaderData::modules() {
// Lazily create the module entry table at first request.
- if (_modules == NULL) {
+ // Lock-free access requires load_ptr_acquire.
+ ModuleEntryTable* modules = load_ptr_acquire(&_modules);
+ if (modules == NULL) {
MutexLocker m1(Module_lock);
- // Check again if _modules has been allocated while we were getting this lock.
- if (_modules != NULL) {
- return _modules;
- }
+ // Check if _modules got allocated while we were waiting for this lock.
+ if ((modules = _modules) == NULL) {
+ modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
+ // Each loader has one unnamed module entry. Create it before
+ // any classes, loaded by this loader, are defined in case
+ // they end up being defined in loader's unnamed module.
+ modules->create_unnamed_module(this);
- ModuleEntryTable* temp_table = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
- // Each loader has one unnamed module entry. Create it before
- // any classes, loaded by this loader, are defined in case
- // they end up being defined in loader's unnamed module.
- temp_table->create_unnamed_module(this);
-
- {
- MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
- // Ensure _modules is stable, since it is examined without a lock
- OrderAccess::storestore();
- _modules = temp_table;
+ {
+ MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
+ // Ensure _modules is stable, since it is examined without a lock
+ OrderAccess::release_store_ptr(&_modules, modules);
+ }
}
}
- return _modules;
+ return modules;
}
oop ClassLoaderData::keep_alive_object() const {
+ assert_locked_or_safepoint(_metaspace_lock);
assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
return is_anonymous() ? _klasses->java_mirror() : class_loader();
}
@@ -499,30 +514,33 @@
// to create smaller arena for Reflection class loaders also.
// The reason for the delayed allocation is because some class loaders are
// simply for delegating with no metadata of their own.
- if (_metaspace == NULL) {
- MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
- // Check again if metaspace has been allocated while we were getting this lock.
- if (_metaspace != NULL) {
- return _metaspace;
- }
- if (this == the_null_class_loader_data()) {
- assert (class_loader() == NULL, "Must be");
- set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
- } else if (is_anonymous()) {
- if (class_loader() != NULL) {
- log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
+ // Lock-free access requires load_ptr_acquire.
+ Metaspace* metaspace = load_ptr_acquire(&_metaspace);
+ if (metaspace == NULL) {
+ MutexLockerEx ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
+ // Check if _metaspace got allocated while we were waiting for this lock.
+ if ((metaspace = _metaspace) == NULL) {
+ if (this == the_null_class_loader_data()) {
+ assert (class_loader() == NULL, "Must be");
+ metaspace = new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
+ } else if (is_anonymous()) {
+ if (class_loader() != NULL) {
+ log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
+ }
+ metaspace = new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType);
+ } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
+ if (class_loader() != NULL) {
+ log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
+ }
+ metaspace = new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
+ } else {
+ metaspace = new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
}
- set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
- } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
- if (class_loader() != NULL) {
- log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
- }
- set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
- } else {
- set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
+ // Ensure _metaspace is stable, since it is examined without a lock
+ OrderAccess::release_store_ptr(&_metaspace, metaspace);
}
}
- return _metaspace;
+ return metaspace;
}
JNIHandleBlock* ClassLoaderData::handles() const { return _handles; }
@@ -638,6 +656,7 @@
#endif // PRODUCT
void ClassLoaderData::verify() {
+ assert_locked_or_safepoint(_metaspace_lock);
oop cl = class_loader();
guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
@@ -656,7 +675,8 @@
}
bool ClassLoaderData::contains_klass(Klass* klass) {
- for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
+ // Lock-free access requires load_ptr_acquire
+ for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
if (k == klass) return true;
}
return false;
@@ -1046,6 +1066,7 @@
// Find the first klass in the CLDG.
while (cld != NULL) {
+ assert_locked_or_safepoint(cld->metaspace_lock());
klass = cld->_klasses;
if (klass != NULL) {
_next_klass = klass;
@@ -1063,6 +1084,7 @@
// No more klasses in the current CLD. Time to find a new CLD.
ClassLoaderData* cld = klass->class_loader_data();
+ assert_locked_or_safepoint(cld->metaspace_lock());
while (next == NULL) {
cld = cld->next();
if (cld == NULL) {