--- a/hotspot/src/share/vm/oops/instanceKlass.cpp Wed Sep 07 15:21:45 2016 +0200
+++ b/hotspot/src/share/vm/oops/instanceKlass.cpp Wed Sep 07 15:25:21 2016 -0400
@@ -3365,88 +3365,119 @@
#if INCLUDE_JVMTI
-// RedefineClasses() support for previous versions:
-int InstanceKlass::_previous_version_count = 0;
-
-// Purge previous versions before adding new previous versions of the class.
-void InstanceKlass::purge_previous_versions(InstanceKlass* ik) {
- if (ik->previous_versions() != NULL) {
- // This klass has previous versions so see what we can cleanup
- // while it is safe to do so.
-
- int deleted_count = 0; // leave debugging breadcrumbs
- int live_count = 0;
- ClassLoaderData* loader_data = ik->class_loader_data();
- assert(loader_data != NULL, "should never be null");
-
- ResourceMark rm;
- log_trace(redefine, class, iklass, purge)("%s: previous versions", ik->external_name());
-
- // previous versions are linked together through the InstanceKlass
- InstanceKlass* pv_node = ik->previous_versions();
- InstanceKlass* last = ik;
- int version = 0;
-
- // check the previous versions list
- for (; pv_node != NULL; ) {
-
- ConstantPool* pvcp = pv_node->constants();
- assert(pvcp != NULL, "cp ref was unexpectedly cleared");
-
- if (!pvcp->on_stack()) {
- // If the constant pool isn't on stack, none of the methods
- // are executing. Unlink this previous_version.
- // The previous version InstanceKlass is on the ClassLoaderData deallocate list
- // so will be deallocated during the next phase of class unloading.
- log_trace(redefine, class, iklass, purge)("previous version " INTPTR_FORMAT " is dead", p2i(pv_node));
- // For debugging purposes.
- pv_node->set_is_scratch_class();
- pv_node->class_loader_data()->add_to_deallocate_list(pv_node);
- pv_node = pv_node->previous_versions();
- last->link_previous_versions(pv_node);
- deleted_count++;
- version++;
- continue;
- } else {
- log_trace(redefine, class, iklass, purge)("previous version " INTPTR_FORMAT " is alive", p2i(pv_node));
- assert(pvcp->pool_holder() != NULL, "Constant pool with no holder");
- guarantee (!loader_data->is_unloading(), "unloaded classes can't be on the stack");
- live_count++;
- }
-
- // At least one method is live in this previous version.
- // Reset dead EMCP methods not to get breakpoints.
- // All methods are deallocated when all of the methods for this class are no
- // longer running.
- Array<Method*>* method_refs = pv_node->methods();
- if (method_refs != NULL) {
- log_trace(redefine, class, iklass, purge)("previous methods length=%d", method_refs->length());
- for (int j = 0; j < method_refs->length(); j++) {
- Method* method = method_refs->at(j);
-
- if (!method->on_stack()) {
- // no breakpoints for non-running methods
- if (method->is_running_emcp()) {
- method->set_running_emcp(false);
- }
- } else {
- assert (method->is_obsolete() || method->is_running_emcp(),
- "emcp method cannot run after emcp bit is cleared");
- log_trace(redefine, class, iklass, purge)
- ("purge: %s(%s): prev method @%d in version @%d is alive",
- method->name()->as_C_string(), method->signature()->as_C_string(), j, version);
+// RedefineClasses() support for previous versions
+
+// Globally, there is at least one previous version of a class to walk
+// during class unloading, which is saved because old methods in the class
+// are still running. Otherwise the previous version list is cleaned up.
+bool InstanceKlass::_has_previous_versions = false;
+
+// Returns true if there are previous versions of a class for class
+// unloading only. Also resets the flag to false. purge_previous_version
+// will set the flag to true if there are any left, i.e., if there's any
+// work to do for next time. This is to avoid the expensive code cache
+// walk in CLDG::do_unloading().
+bool InstanceKlass::has_previous_versions_and_reset() {
+ bool ret = _has_previous_versions;
+ log_trace(redefine, class, iklass, purge)("Class unloading: has_previous_versions = %s",
+ ret ? "true" : "false");
+ _has_previous_versions = false;
+ return ret;
+}
+
+// Purge previous versions before adding new previous versions of the class and
+// during class unloading.
+void InstanceKlass::purge_previous_version_list() {
+ assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
+ assert(has_been_redefined(), "Should only be called for main class");
+
+ // Quick exit.
+ if (previous_versions() == NULL) {
+ return;
+ }
+
+ // This klass has previous versions so see what we can cleanup
+ // while it is safe to do so.
+
+ int deleted_count = 0; // leave debugging breadcrumbs
+ int live_count = 0;
+ ClassLoaderData* loader_data = class_loader_data();
+ assert(loader_data != NULL, "should never be null");
+
+ ResourceMark rm;
+ log_trace(redefine, class, iklass, purge)("%s: previous versions", external_name());
+
+ // previous versions are linked together through the InstanceKlass
+ InstanceKlass* pv_node = previous_versions();
+ InstanceKlass* last = this;
+ int version = 0;
+
+ // check the previous versions list
+ for (; pv_node != NULL; ) {
+
+ ConstantPool* pvcp = pv_node->constants();
+ assert(pvcp != NULL, "cp ref was unexpectedly cleared");
+
+ if (!pvcp->on_stack()) {
+ // If the constant pool isn't on stack, none of the methods
+ // are executing. Unlink this previous_version.
+ // The previous version InstanceKlass is on the ClassLoaderData deallocate list
+ // so will be deallocated during the next phase of class unloading.
+ log_trace(redefine, class, iklass, purge)
+ ("previous version " INTPTR_FORMAT " is dead.", p2i(pv_node));
+ // For debugging purposes.
+ pv_node->set_is_scratch_class();
+ // Unlink from previous version list.
+ assert(pv_node->class_loader_data() == loader_data, "wrong loader_data");
+ InstanceKlass* next = pv_node->previous_versions();
+ pv_node->link_previous_versions(NULL); // point next to NULL
+ last->link_previous_versions(next);
+ // Add to the deallocate list after unlinking
+ loader_data->add_to_deallocate_list(pv_node);
+ pv_node = next;
+ deleted_count++;
+ version++;
+ continue;
+ } else {
+ log_trace(redefine, class, iklass, purge)("previous version " INTPTR_FORMAT " is alive", p2i(pv_node));
+ assert(pvcp->pool_holder() != NULL, "Constant pool with no holder");
+ guarantee (!loader_data->is_unloading(), "unloaded classes can't be on the stack");
+ live_count++;
+ // found a previous version for next time we do class unloading
+ _has_previous_versions = true;
+ }
+
+ // At least one method is live in this previous version.
+ // Reset dead EMCP methods not to get breakpoints.
+ // All methods are deallocated when all of the methods for this class are no
+ // longer running.
+ Array<Method*>* method_refs = pv_node->methods();
+ if (method_refs != NULL) {
+ log_trace(redefine, class, iklass, purge)("previous methods length=%d", method_refs->length());
+ for (int j = 0; j < method_refs->length(); j++) {
+ Method* method = method_refs->at(j);
+
+ if (!method->on_stack()) {
+ // no breakpoints for non-running methods
+ if (method->is_running_emcp()) {
+ method->set_running_emcp(false);
}
+ } else {
+ assert (method->is_obsolete() || method->is_running_emcp(),
+ "emcp method cannot run after emcp bit is cleared");
+ log_trace(redefine, class, iklass, purge)
+ ("purge: %s(%s): prev method @%d in version @%d is alive",
+ method->name()->as_C_string(), method->signature()->as_C_string(), j, version);
}
}
- // next previous version
- last = pv_node;
- pv_node = pv_node->previous_versions();
- version++;
}
- log_trace(redefine, class, iklass, purge)
- ("previous version stats: live=%d, deleted=%d",
- live_count, deleted_count);
+ // next previous version
+ last = pv_node;
+ pv_node = pv_node->previous_versions();
+ version++;
}
+ log_trace(redefine, class, iklass, purge)
+ ("previous version stats: live=%d, deleted=%d", live_count, deleted_count);
}
void InstanceKlass::mark_newly_obsolete_methods(Array<Method*>* old_methods,
@@ -3518,8 +3549,8 @@
log_trace(redefine, class, iklass, add)
("adding previous version ref for %s, EMCP_cnt=%d", scratch_class->external_name(), emcp_method_count);
- // Clean out old previous versions
- purge_previous_versions(this);
+ // Clean out old previous versions for this class
+ purge_previous_version_list();
// Mark newly obsolete methods in remaining previous versions. An EMCP method from
// a previous redefinition may be made obsolete by this redefinition.
@@ -3536,8 +3567,6 @@
// For debugging purposes.
scratch_class->set_is_scratch_class();
scratch_class->class_loader_data()->add_to_deallocate_list(scratch_class());
- // Update count for class unloading.
- _previous_version_count--;
return;
}
@@ -3565,12 +3594,12 @@
}
// Add previous version if any methods are still running.
- log_trace(redefine, class, iklass, add)("scratch class added; one of its methods is on_stack");
+ // Set has_previous_version flag for processing during class unloading.
+ _has_previous_versions = true;
+ log_trace(redefine, class, iklass, add) ("scratch class added; one of its methods is on_stack.");
assert(scratch_class->previous_versions() == NULL, "shouldn't have a previous version");
scratch_class->link_previous_versions(previous_versions());
link_previous_versions(scratch_class());
- // Update count for class unloading.
- _previous_version_count++;
} // end add_previous_version()
#endif // INCLUDE_JVMTI