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8159262: Walking PackageEntry Export and ModuleEntry Reads Must Occur Only When Neccessary And Wait Until ClassLoader's Aliveness Determined

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Fixed an issue in class unloading to delay walk until class loader's aliveness is determined of modularity lists to remove dead modules

Reviewed-by: coleenp, dholmes, sspitsyn, zgu
This commit is contained in:
Lois Foltan 2016-06-28 10:11:01 -04:00
parent 651e15fda6
commit 92eb334c91
16 changed files with 807 additions and 46 deletions
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59
hotspot/src/share/vm/classfile/packageEntry.cpp
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@ -25,6 +25,7 @@
#include "precompiled.hpp"
#include "classfile/moduleEntry.hpp"
#include "classfile/packageEntry.hpp"
#include "logging/log.hpp"
#include "memory/resourceArea.hpp"
#include "oops/symbol.hpp"
#include "runtime/handles.inline.hpp"
@ -53,12 +54,40 @@ void PackageEntry::add_qexport(ModuleEntry* m) {
if (!has_qual_exports_list()) {
// Lazily create a package's qualified exports list.
// Initial size is small, do not anticipate export lists to be large.
_qualified_exports =
new (ResourceObj::C_HEAP, mtModule) GrowableArray<ModuleEntry*>(QUAL_EXP_SIZE, true);
_qualified_exports = new (ResourceObj::C_HEAP, mtModule) GrowableArray<ModuleEntry*>(QUAL_EXP_SIZE, true);
}
// Determine, based on this newly established export to module m,
// if this package's export list should be walked at a GC safepoint.
set_export_walk_required(m->loader_data());
// Establish exportability to module m
_qualified_exports->append_if_missing(m);
}
// If the module's loader, that an export is being established to, is
// not the same loader as this module's and is not one of the 3 builtin
// class loaders, then this package's export list must be walked at GC
// safepoint. Modules have the same life cycle as their defining class
// loaders and should be removed if dead.
void PackageEntry::set_export_walk_required(ClassLoaderData* m_loader_data) {
assert_locked_or_safepoint(Module_lock);
ModuleEntry* this_pkg_mod = module();
if (!_must_walk_exports &&
(this_pkg_mod == NULL || this_pkg_mod->loader_data() != m_loader_data) &&
!m_loader_data->is_builtin_class_loader_data()) {
_must_walk_exports = true;
if (log_is_enabled(Trace, modules)) {
ResourceMark rm;
assert(name() != NULL, "PackageEntry without a valid name");
log_trace(modules)("PackageEntry::set_export_walk_required(): package %s defined in module %s, exports list must be walked",
name()->as_C_string(),
(this_pkg_mod == NULL || this_pkg_mod->name() == NULL) ?
UNNAMED_MODULE : this_pkg_mod->name()->as_C_string());
}
}
}
// Set the package's exported states based on the value of the ModuleEntry.
void PackageEntry::set_exported(ModuleEntry* m) {
MutexLocker m1(Module_lock);
@ -96,14 +125,34 @@ void PackageEntry::set_is_exported_allUnnamed() {
// Remove dead module entries within the package's exported list.
void PackageEntry::purge_qualified_exports() {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
if (_qualified_exports != NULL) {
if (_must_walk_exports &&
_qualified_exports != NULL &&
!_qualified_exports->is_empty()) {
ModuleEntry* pkg_module = module();
// This package's _must_walk_exports flag will be reset based
// on the remaining live modules on the exports list.
_must_walk_exports = false;
if (log_is_enabled(Trace, modules)) {
ResourceMark rm;
assert(name() != NULL, "PackageEntry without a valid name");
ModuleEntry* pkg_mod = module();
log_trace(modules)("PackageEntry::purge_qualified_exports(): package %s defined in module %s, exports list being walked",
name()->as_C_string(),
(pkg_mod == NULL || pkg_mod->name() == NULL) ? UNNAMED_MODULE : pkg_mod->name()->as_C_string());
}
// Go backwards because this removes entries that are dead.
int len = _qualified_exports->length();
for (int idx = len - 1; idx >= 0; idx--) {
ModuleEntry* module_idx = _qualified_exports->at(idx);
ClassLoaderData* cld = module_idx->loader();
if (cld->is_unloading()) {
ClassLoaderData* cld_idx = module_idx->loader_data();
if (cld_idx->is_unloading()) {
_qualified_exports->delete_at(idx);
} else {
// Update the need to walk this package's exports based on live modules
set_export_walk_required(cld_idx);
}
}
}