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8213107: Make ClassLoaderDataGraph iterator skip unloaded CLDs

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With concurrent class unloading, the CLDG could contain unloaded CLDs while iterating in a safepoint

Reviewed-by: lfoltan, eosterlund
This commit is contained in:
Coleen Phillimore 2018-10-31 07:06:54 -04:00
parent f66d1f3d9e
commit adb1dcdcc2
1 changed files with 23 additions and 33 deletions
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56
src/hotspot/share/classfile/classLoaderDataGraph.cpp
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@ -287,54 +287,50 @@ class ClassLoaderDataGraphIterator : public StackObj {
Handle _holder;
Thread* _thread;
void hold_next() {
if (_next != NULL) {
_holder = Handle(_thread, _next->holder_phantom());
}
}
public:
ClassLoaderDataGraphIterator() : _next(ClassLoaderDataGraph::_head) {
_thread = Thread::current();
assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
hold_next();
}
bool repeat() const {
return _next != NULL;
}
ClassLoaderData* get_next() {
ClassLoaderData* next = _next;
if (_next != NULL) {
_next = _next->next();
hold_next();
ClassLoaderData* cld = _next;
// Skip already unloaded CLD for concurrent unloading.
while (cld != NULL && !cld->is_alive()) {
cld = cld->next();
}
return next;
if (cld != NULL) {
// Keep cld that is being returned alive.
_holder = Handle(_thread, cld->holder_phantom());
_next = cld->next();
} else {
_next = NULL;
}
return cld;
}
};
// These functions assume that the caller has locked the ClassLoaderDataGraph_lock
// if they are not calling the function from a safepoint.
void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->classes_do(klass_closure);
}
}
void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->classes_do(f);
}
}
void ClassLoaderDataGraph::methods_do(void f(Method*)) {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->methods_do(f);
}
}
@ -342,8 +338,7 @@ void ClassLoaderDataGraph::methods_do(void f(Method*)) {
void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
assert_locked_or_safepoint(Module_lock);
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->modules_do(f);
}
}
@ -361,8 +356,7 @@ void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
assert_locked_or_safepoint(Module_lock);
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->packages_do(f);
}
}
@ -379,8 +373,7 @@ void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->loaded_classes_do(klass_closure);
}
}
@ -404,8 +397,7 @@ void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
}
#define FOR_ALL_DICTIONARY(X) ClassLoaderDataGraphIterator iter; \
ClassLoaderData* X; \
while ((X = iter.get_next()) != NULL) \
while (ClassLoaderData* X = iter.get_next()) \
if (X->dictionary() != NULL)
// Walk classes in the loaded class dictionaries in various forms.
@ -696,16 +688,14 @@ extern "C" int print_loader_data_graph() {
void ClassLoaderDataGraph::verify() {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->verify();
}
}
void ClassLoaderDataGraph::print_on(outputStream * const out) {
ClassLoaderDataGraphIterator iter;
while (iter.repeat()) {
ClassLoaderData* cld = iter.get_next();
while (ClassLoaderData* cld = iter.get_next()) {
cld->print_on(out);
}
}