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8182397: Race in field updates when creating ArrayKlasses can lead to crash

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Update array_klass field in component mirror after klass.java_mirror field for concurrent readers in compiled code

Reviewed-by: aph, kbarrett
This commit is contained in:
Coleen Phillimore 2017-07-24 17:46:06 -04:00
parent fe6e4eb1e0
commit fd08aa9cef
5 changed files with 108 additions and 16 deletions
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33
hotspot/src/share/vm/classfile/javaClasses.cpp
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@ -818,6 +818,7 @@ void java_lang_Class::set_mirror_module_field(Klass* k, Handle mirror, Handle mo
void java_lang_Class::create_mirror(Klass* k, Handle class_loader,
Handle module, Handle protection_domain, TRAPS) {
assert(k != NULL, "Use create_basic_type_mirror for primitive types");
assert(k->java_mirror() == NULL, "should only assign mirror once");
// Use this moment of initialization to cache modifier_flags also,
// to support Class.getModifiers(). Instance classes recalculate
@ -831,11 +832,10 @@ void java_lang_Class::create_mirror(Klass* k, Handle class_loader,
// Allocate mirror (java.lang.Class instance)
oop mirror_oop = InstanceMirrorKlass::cast(SystemDictionary::Class_klass())->allocate_instance(k, CHECK);
Handle mirror(THREAD, mirror_oop);
Handle comp_mirror;
// Setup indirection from mirror->klass
if (k != NULL) {
java_lang_Class::set_klass(mirror(), k);
}
java_lang_Class::set_klass(mirror(), k);
InstanceMirrorKlass* mk = InstanceMirrorKlass::cast(mirror->klass());
assert(oop_size(mirror()) == mk->instance_size(k), "should have been set");
@ -844,22 +844,22 @@ void java_lang_Class::create_mirror(Klass* k, Handle class_loader,
// It might also have a component mirror. This mirror must already exist.
if (k->is_array_klass()) {
oop comp_mirror;
if (k->is_typeArray_klass()) {
BasicType type = TypeArrayKlass::cast(k)->element_type();
comp_mirror = Universe::java_mirror(type);
comp_mirror = Handle(THREAD, Universe::java_mirror(type));
} else {
assert(k->is_objArray_klass(), "Must be");
Klass* element_klass = ObjArrayKlass::cast(k)->element_klass();
assert(element_klass != NULL, "Must have an element klass");
comp_mirror = element_klass->java_mirror();
comp_mirror = Handle(THREAD, element_klass->java_mirror());
}
assert(comp_mirror != NULL, "must have a mirror");
assert(comp_mirror() != NULL, "must have a mirror");
// Two-way link between the array klass and its component mirror:
// (array_klass) k -> mirror -> component_mirror -> array_klass -> k
set_component_mirror(mirror(), comp_mirror);
set_array_klass(comp_mirror, k);
set_component_mirror(mirror(), comp_mirror());
// See below for ordering dependencies between field array_klass in component mirror
// and java_mirror in this klass.
} else {
assert(k->is_instance_klass(), "Must be");
@ -881,10 +881,13 @@ void java_lang_Class::create_mirror(Klass* k, Handle class_loader,
// set the module field in the java_lang_Class instance
set_mirror_module_field(k, mirror, module, THREAD);
// Setup indirection from klass->mirror last
// Setup indirection from klass->mirror
// after any exceptions can happen during allocations.
if (k != NULL) {
k->set_java_mirror(mirror());
k->set_java_mirror(mirror());
if (comp_mirror() != NULL) {
// Set after k->java_mirror() is published, because compiled code running
// concurrently doesn't expect a k to have a null java_mirror.
release_set_array_klass(comp_mirror(), k);
}
} else {
if (fixup_mirror_list() == NULL) {
@ -989,7 +992,7 @@ oop java_lang_Class::create_basic_type_mirror(const char* basic_type_name, Basic
if (type != T_VOID) {
Klass* aklass = Universe::typeArrayKlassObj(type);
assert(aklass != NULL, "correct bootstrap");
set_array_klass(java_class, aklass);
release_set_array_klass(java_class, aklass);
}
#ifdef ASSERT
InstanceMirrorKlass* mk = InstanceMirrorKlass::cast(SystemDictionary::Class_klass());
@ -1086,9 +1089,9 @@ Klass* java_lang_Class::array_klass(oop java_class) {
}
void java_lang_Class::set_array_klass(oop java_class, Klass* klass) {
void java_lang_Class::release_set_array_klass(oop java_class, Klass* klass) {
assert(klass->is_klass() && klass->is_array_klass(), "should be array klass");
java_class->metadata_field_put(_array_klass_offset, klass);
java_class->release_metadata_field_put(_array_klass_offset, klass);
}