--- old/src/share/vm/oops/instanceKlass.cpp 2014-08-22 10:18:43.574639000 -0400 +++ new/src/share/vm/oops/instanceKlass.cpp 2014-08-22 10:18:40.983200000 -0400 @@ -2437,16 +2437,6 @@ assert(breakpoints() == 0x0, "should have cleared breakpoints"); } - // deallocate information about previous versions - if (_previous_versions != NULL) { - for (int i = _previous_versions->length() - 1; i >= 0; i--) { - PreviousVersionNode * pv_node = _previous_versions->at(i); - delete pv_node; - } - delete _previous_versions; - _previous_versions = NULL; - } - // deallocate the cached class file if (_cached_class_file != NULL) { os::free(_cached_class_file, mtClass); @@ -3020,16 +3010,17 @@ st->print(BULLET"field type annotations: "); fields_type_annotations()->print_value_on(st); st->cr(); { bool have_pv = false; - PreviousVersionWalker pvw(Thread::current(), (InstanceKlass*)this); - for (PreviousVersionNode * pv_node = pvw.next_previous_version(); - pv_node != NULL; pv_node = pvw.next_previous_version()) { + // previous versions are linked together through the InstanceKlass + for (InstanceKlass* pv_node = _previous_versions; + pv_node != NULL; + pv_node = pv_node->previous_versions()) { if (!have_pv) st->print(BULLET"previous version: "); have_pv = true; - pv_node->prev_constant_pool()->print_value_on(st); + pv_node->constants()->print_value_on(st); } if (have_pv) st->cr(); - } // pvw is cleaned up + } if (generic_signature() != NULL) { st->print(BULLET"generic signature: "); @@ -3443,92 +3434,86 @@ // RedefineClasses() support for previous versions: // Purge previous versions -static void purge_previous_versions_internal(InstanceKlass* ik, int emcp_method_count) { +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() == NULL ? - ClassLoaderData::the_null_class_loader_data() : - ik->class_loader_data(); + ClassLoaderData* loader_data = ik->class_loader_data(); + assert(loader_data != NULL, "should never be null"); // RC_TRACE macro has an embedded ResourceMark - RC_TRACE(0x00000200, ("purge: %s: previous version length=%d", - ik->external_name(), ik->previous_versions()->length())); + RC_TRACE(0x00000200, ("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; - for (int i = ik->previous_versions()->length() - 1; i >= 0; i--) { - // check the previous versions array - PreviousVersionNode * pv_node = ik->previous_versions()->at(i); - ConstantPool* cp_ref = pv_node->prev_constant_pool(); - assert(cp_ref != NULL, "cp ref was unexpectedly cleared"); + // check the previous versions list + for (; pv_node != NULL; ) { + + ConstantPool* pvcp = pv_node->constants(); + assert(pvcp != NULL, "cp ref was unexpectedly cleared"); - ConstantPool* pvcp = cp_ref; if (!pvcp->on_stack()) { // If the constant pool isn't on stack, none of the methods - // are executing. Delete all the methods, the constant pool and - // and this previous version node. - GrowableArray* method_refs = pv_node->prev_EMCP_methods(); - if (method_refs != NULL) { - for (int j = method_refs->length() - 1; j >= 0; j--) { - Method* method = method_refs->at(j); - assert(method != NULL, "method ref was unexpectedly cleared"); - method_refs->remove_at(j); - // method will be freed with associated class. - } - } - // Remove the constant pool - delete pv_node; - // Since we are traversing the array backwards, we don't have to - // do anything special with the index. - ik->previous_versions()->remove_at(i); + // 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. + pv_node = pv_node->previous_versions(); + last->link_previous_versions(pv_node); deleted_count++; continue; } else { - RC_TRACE(0x00000200, ("purge: previous version @%d is alive", i)); + RC_TRACE(0x00000200, ("purge: previous version " INTPTR_FORMAT " is alive", + 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, clean out - // the others or mark them as obsolete. - GrowableArray* method_refs = pv_node->prev_EMCP_methods(); + // At least one method is live in this previous version so clean its MethodData. + // Reset dead EMCP methods not to get breakpoints. + Array* method_refs = pv_node->methods(); if (method_refs != NULL) { RC_TRACE(0x00000200, ("purge: previous methods length=%d", method_refs->length())); - for (int j = method_refs->length() - 1; j >= 0; j--) { + for (int j = 0; j < method_refs->length(); j++) { Method* method = method_refs->at(j); - assert(method != NULL, "method ref was unexpectedly cleared"); - // Remove the emcp method if it's not executing - // If it's been made obsolete by a redefinition of a non-emcp - // method, mark it as obsolete but leave it to clean up later. if (!method->on_stack()) { - method_refs->remove_at(j); - } else if (emcp_method_count == 0) { - method->set_is_obsolete(); + if (method->is_running_emcp()) { + method->set_running_emcp(false); // no breakpoints for non-running methods + } } else { // RC_TRACE macro has an embedded ResourceMark RC_TRACE(0x00000200, ("purge: %s(%s): prev method @%d in version @%d is alive", method->name()->as_C_string(), - method->signature()->as_C_string(), j, i)); + method->signature()->as_C_string(), j, version)); if (method->method_data() != NULL) { - // Clean out any weak method links + // Clean out any weak method links for running methods + // (also should include not EMCP methods) method->method_data()->clean_weak_method_links(); } } } } + // next previous version + last = pv_node; + pv_node = pv_node->previous_versions(); + version++; } - assert(ik->previous_versions()->length() == live_count, "sanity check"); RC_TRACE(0x00000200, ("purge: previous version stats: live=%d, deleted=%d", live_count, deleted_count)); } + // Clean MethodData of this class's methods so they don't refer to + // old methods that are no longer running. Array* methods = ik->methods(); int num_methods = methods->length(); for (int index2 = 0; index2 < num_methods; ++index2) { @@ -3538,122 +3523,30 @@ } } -// External interface for use during class unloading. -void InstanceKlass::purge_previous_versions(InstanceKlass* ik) { - // Call with >0 emcp methods since they are not currently being redefined. - purge_previous_versions_internal(ik, 1); -} - - -// Potentially add an information node that contains pointers to the -// interesting parts of the previous version of the_class. -// This is also where we clean out any unused references. -// Note that while we delete nodes from the _previous_versions -// array, we never delete the array itself until the klass is -// unloaded. The has_been_redefined() query depends on that fact. -// -void InstanceKlass::add_previous_version(instanceKlassHandle ikh, - BitMap* emcp_methods, int emcp_method_count) { - assert(Thread::current()->is_VM_thread(), - "only VMThread can add previous versions"); - - if (_previous_versions == NULL) { - // This is the first previous version so make some space. - // Start with 2 elements under the assumption that the class - // won't be redefined much. - _previous_versions = new (ResourceObj::C_HEAP, mtClass) - GrowableArray(2, true); - } - - ConstantPool* cp_ref = ikh->constants(); - - // RC_TRACE macro has an embedded ResourceMark - RC_TRACE(0x00000400, ("adding previous version ref for %s @%d, EMCP_cnt=%d " - "on_stack=%d", - ikh->external_name(), _previous_versions->length(), emcp_method_count, - cp_ref->on_stack())); - - // If the constant pool for this previous version of the class - // is not marked as being on the stack, then none of the methods - // in this previous version of the class are on the stack so - // we don't need to create a new PreviousVersionNode. However, - // we still need to examine older previous versions below. - Array* old_methods = ikh->methods(); - - if (cp_ref->on_stack()) { - PreviousVersionNode * pv_node = NULL; - if (emcp_method_count == 0) { - // non-shared ConstantPool gets a reference - pv_node = new PreviousVersionNode(cp_ref, NULL); - RC_TRACE(0x00000400, - ("add: all methods are obsolete; flushing any EMCP refs")); - } else { - int local_count = 0; - GrowableArray* method_refs = new (ResourceObj::C_HEAP, mtClass) - GrowableArray(emcp_method_count, true); - for (int i = 0; i < old_methods->length(); i++) { - if (emcp_methods->at(i)) { - // this old method is EMCP. Save it only if it's on the stack - Method* old_method = old_methods->at(i); - if (old_method->on_stack()) { - method_refs->append(old_method); - } - if (++local_count >= emcp_method_count) { - // no more EMCP methods so bail out now - break; - } - } - } - // non-shared ConstantPool gets a reference - pv_node = new PreviousVersionNode(cp_ref, method_refs); - } - // append new previous version. - _previous_versions->append(pv_node); - } - - // Since the caller is the VMThread and we are at a safepoint, this - // is a good time to clear out unused references. - - RC_TRACE(0x00000400, ("add: previous version length=%d", - _previous_versions->length())); - - // Purge previous versions not executing on the stack - purge_previous_versions_internal(this, emcp_method_count); - +void InstanceKlass::mark_newly_obsolete_methods(Array* old_methods, + int emcp_method_count) { int obsolete_method_count = old_methods->length() - emcp_method_count; if (emcp_method_count != 0 && obsolete_method_count != 0 && - _previous_versions->length() > 0) { + _previous_versions != NULL) { // We have a mix of obsolete and EMCP methods so we have to // clear out any matching EMCP method entries the hard way. int local_count = 0; for (int i = 0; i < old_methods->length(); i++) { - if (!emcp_methods->at(i)) { + Method* old_method = old_methods->at(i); + if (old_method->is_obsolete()) { // only obsolete methods are interesting - Method* old_method = old_methods->at(i); Symbol* m_name = old_method->name(); Symbol* m_signature = old_method->signature(); - // we might not have added the last entry - for (int j = _previous_versions->length() - 1; j >= 0; j--) { - // check the previous versions array for non executing obsolete methods - PreviousVersionNode * pv_node = _previous_versions->at(j); - - GrowableArray* method_refs = pv_node->prev_EMCP_methods(); - if (method_refs == NULL) { - // We have run into a PreviousVersion generation where - // all methods were made obsolete during that generation's - // RedefineClasses() operation. At the time of that - // operation, all EMCP methods were flushed so we don't - // have to go back any further. - // - // A NULL method_refs is different than an empty method_refs. - // We cannot infer any optimizations about older generations - // from an empty method_refs for the current generation. - break; - } + // previous versions are linked together through the InstanceKlass + int j = 0; + for (InstanceKlass* prev_version = _previous_versions; + prev_version != NULL; + prev_version = prev_version->previous_versions(), j++) { - for (int k = method_refs->length() - 1; k >= 0; k--) { + Array* method_refs = prev_version->methods(); + for (int k = 0; k < method_refs->length(); k++) { Method* method = method_refs->at(k); if (!method->is_obsolete() && @@ -3661,14 +3554,11 @@ method->signature() == m_signature) { // The current RedefineClasses() call has made all EMCP // versions of this method obsolete so mark it as obsolete - // and remove the reference. RC_TRACE(0x00000400, ("add: %s(%s): flush obsolete method @%d in version @%d", m_name->as_C_string(), m_signature->as_C_string(), k, j)); method->set_is_obsolete(); - // Leave obsolete methods on the previous version list to - // clean up later. break; } } @@ -3676,9 +3566,9 @@ // The previous loop may not find a matching EMCP method, but // that doesn't mean that we can optimize and not go any // further back in the PreviousVersion generations. The EMCP - // method for this generation could have already been deleted, + // method for this generation could have already been made obsolete, // but there still may be an older EMCP method that has not - // been deleted. + // been made obsolete. } if (++local_count >= obsolete_method_count) { @@ -3688,18 +3578,62 @@ } } } -} // end add_previous_version() +} +// Save the scratch_class as the previous version if any of the methods are running. +// The previous_versions are used to set breakpoints in EMCP methods and they are +// also used to clean MethodData links to redefined methods that are no longer running. +void InstanceKlass::add_previous_version(instanceKlassHandle scratch_class, + int emcp_method_count) { + assert(Thread::current()->is_VM_thread(), + "only VMThread can add previous versions"); + + // RC_TRACE macro has an embedded ResourceMark + RC_TRACE(0x00000400, ("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); + + // Mark newly obsolete methods in remaining previous versions. An EMCP method from + // a previous redefinition may be made obsolete by this redefinition. + Array* old_methods = scratch_class->methods(); + mark_newly_obsolete_methods(old_methods, emcp_method_count); + + // If the constant pool for this previous version of the class + // is not marked as being on the stack, then none of the methods + // in this previous version of the class are on the stack so + // we don't need to add this as a previous version. + ConstantPool* cp_ref = scratch_class->constants(); + if (cp_ref->on_stack()) { + if (emcp_method_count == 0) { + RC_TRACE(0x00000400, ("add: all methods are obsolete; no added EMCP refs")); + } else { + for (int i = 0; i < old_methods->length(); i++) { + Method* old_method = old_methods->at(i); + if (!old_method->is_obsolete() && old_method->on_stack()) { + // if EMCP method (not obsolete) is on the stack, mark as EMCP so that + // we add breakpoints for it. + old_method->set_running_emcp(true); + // At least one emcp method is still running + RC_TRACE(0x00000400, ("add: EMCP method %s is on_stack", old_method->name_and_sig_as_C_string())); + } + } + } -// Determine if InstanceKlass has a previous version. -bool InstanceKlass::has_previous_version() const { - return (_previous_versions != NULL && _previous_versions->length() > 0); -} // end has_previous_version() + RC_TRACE(0x00000400, ("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()); + } else { + RC_TRACE(0x00000400, ("add: scratch class not added; no methods are running")); + } +} // end add_previous_version() Method* InstanceKlass::method_with_idnum(int idnum) { Method* m = NULL; - if (idnum < methods()->length()) { + if (idnum < methods()->length()) { m = methods()->at(idnum); } if (m == NULL || m->method_idnum() != idnum) { @@ -3722,61 +3656,3 @@ unsigned char * InstanceKlass::get_cached_class_file_bytes() { return VM_RedefineClasses::get_cached_class_file_bytes(_cached_class_file); } - - -// Construct a PreviousVersionNode entry for the array hung off -// the InstanceKlass. -PreviousVersionNode::PreviousVersionNode(ConstantPool* prev_constant_pool, - GrowableArray* prev_EMCP_methods) { - - _prev_constant_pool = prev_constant_pool; - _prev_EMCP_methods = prev_EMCP_methods; -} - - -// Destroy a PreviousVersionNode -PreviousVersionNode::~PreviousVersionNode() { - if (_prev_constant_pool != NULL) { - _prev_constant_pool = NULL; - } - - if (_prev_EMCP_methods != NULL) { - delete _prev_EMCP_methods; - } -} - -// Construct a helper for walking the previous versions array -PreviousVersionWalker::PreviousVersionWalker(Thread* thread, InstanceKlass *ik) { - _thread = thread; - _previous_versions = ik->previous_versions(); - _current_index = 0; - _current_p = NULL; - _current_constant_pool_handle = constantPoolHandle(thread, ik->constants()); -} - - -// Return the interesting information for the next previous version -// of the klass. Returns NULL if there are no more previous versions. -PreviousVersionNode* PreviousVersionWalker::next_previous_version() { - if (_previous_versions == NULL) { - // no previous versions so nothing to return - return NULL; - } - - _current_p = NULL; // reset to NULL - _current_constant_pool_handle = NULL; - - int length = _previous_versions->length(); - - while (_current_index < length) { - PreviousVersionNode * pv_node = _previous_versions->at(_current_index++); - - // Save a handle to the constant pool for this previous version, - // which keeps all the methods from being deallocated. - _current_constant_pool_handle = constantPoolHandle(_thread, pv_node->prev_constant_pool()); - _current_p = pv_node; - return pv_node; - } - - return NULL; -} // end next_previous_version()