# HG changeset patch # User acorn # Date 1357857500 18000 # Node ID 3916ac601e043362c07a67558fa08d08bcbf23f3 # Parent fb364e5a0b34334c517901f11ac68dba70189bc6 7199207: NPG: Crash in PlaceholderTable::verify after StackOverflow Summary: Reduce scope of placeholder table entries to improve cleanup Reviewed-by: dholmes, coleenp diff -r fb364e5a0b34 -r 3916ac601e04 hotspot/src/share/vm/classfile/placeholders.cpp --- a/hotspot/src/share/vm/classfile/placeholders.cpp Wed Jan 09 12:10:25 2013 -0800 +++ b/hotspot/src/share/vm/classfile/placeholders.cpp Thu Jan 10 17:38:20 2013 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -142,7 +142,7 @@ } -// placeholder used to track class loading internal states +// placeholder is used to track class loading internal states // placeholder existence now for loading superclass/superinterface // superthreadQ tracks class circularity, while loading superclass/superinterface // loadInstanceThreadQ tracks load_instance_class calls @@ -153,15 +153,17 @@ // All claimants remove SeenThread after completing action // On removal: if definer and all queues empty, remove entry // Note: you can be in both placeholders and systemDictionary -// see parse_stream for redefine classes // Therefore - must always check SD first // Ignores the case where entry is not found void PlaceholderTable::find_and_remove(int index, unsigned int hash, - Symbol* name, ClassLoaderData* loader_data, Thread* thread) { + Symbol* name, ClassLoaderData* loader_data, + classloadAction action, + Thread* thread) { assert_locked_or_safepoint(SystemDictionary_lock); PlaceholderEntry *probe = get_entry(index, hash, name, loader_data); if (probe != NULL) { - // No other threads using this entry + probe->remove_seen_thread(thread, action); + // If no other threads using this entry, and this thread is not using this entry for other states if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL) && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) { remove_entry(index, hash, name, loader_data); diff -r fb364e5a0b34 -r 3916ac601e04 hotspot/src/share/vm/classfile/placeholders.hpp --- a/hotspot/src/share/vm/classfile/placeholders.hpp Wed Jan 09 12:10:25 2013 -0800 +++ b/hotspot/src/share/vm/classfile/placeholders.hpp Thu Jan 10 17:38:20 2013 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -82,7 +82,7 @@ }; // find_and_add returns probe pointer - old or new - // If no entry exists, add a placeholder entry and push SeenThread + // If no entry exists, add a placeholder entry and push SeenThread for classloadAction // If entry exists, reuse entry and push SeenThread for classloadAction PlaceholderEntry* find_and_add(int index, unsigned int hash, Symbol* name, ClassLoaderData* loader_data, @@ -92,9 +92,11 @@ void remove_entry(int index, unsigned int hash, Symbol* name, ClassLoaderData* loader_data); -// Remove placeholder information + // find_and_remove first removes SeenThread for classloadAction + // If all queues are empty and definer is null, remove the PlacheholderEntry completely void find_and_remove(int index, unsigned int hash, - Symbol* name, ClassLoaderData* loader_data, Thread* thread); + Symbol* name, ClassLoaderData* loader_data, + classloadAction action, Thread* thread); // GC support. void classes_do(KlassClosure* f); diff -r fb364e5a0b34 -r 3916ac601e04 hotspot/src/share/vm/classfile/systemDictionary.cpp --- a/hotspot/src/share/vm/classfile/systemDictionary.cpp Wed Jan 09 12:10:25 2013 -0800 +++ b/hotspot/src/share/vm/classfile/systemDictionary.cpp Thu Jan 10 17:38:20 2013 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -172,7 +172,7 @@ assert(klass_h() == NULL, "Should not have result with exception pending"); Handle e(THREAD, PENDING_EXCEPTION); CLEAR_PENDING_EXCEPTION; - THROW_MSG_CAUSE_0(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e); + THROW_MSG_CAUSE_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string(), e); } else { return NULL; } @@ -181,9 +181,9 @@ if (klass_h() == NULL) { ResourceMark rm(THREAD); if (throw_error) { - THROW_MSG_0(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string()); + THROW_MSG_NULL(vmSymbols::java_lang_NoClassDefFoundError(), class_name->as_C_string()); } else { - THROW_MSG_0(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string()); + THROW_MSG_NULL(vmSymbols::java_lang_ClassNotFoundException(), class_name->as_C_string()); } } return (Klass*)klass_h(); @@ -343,29 +343,29 @@ } if (throw_circularity_error) { ResourceMark rm(THREAD); - THROW_MSG_0(vmSymbols::java_lang_ClassCircularityError(), child_name->as_C_string()); + THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), child_name->as_C_string()); } // java.lang.Object should have been found above assert(class_name != NULL, "null super class for resolving"); // Resolve the super class or interface, check results on return - Klass* superk = NULL; - superk = SystemDictionary::resolve_or_null(class_name, + Klass* superk = SystemDictionary::resolve_or_null(class_name, class_loader, protection_domain, THREAD); KlassHandle superk_h(THREAD, superk); - // Note: clean up of placeholders currently in callers of - // resolve_super_or_fail - either at update_dictionary time - // or on error + // Clean up of placeholders moved so that each classloadAction registrar self-cleans up + // It is no longer necessary to keep the placeholder table alive until update_dictionary + // or error. GC used to walk the placeholder table as strong roots. + // The instanceKlass is kept alive because the class loader is on the stack, + // which keeps the loader_data alive, as well as all instanceKlasses in + // the loader_data. parseClassFile adds the instanceKlass to loader_data. { - MutexLocker mu(SystemDictionary_lock, THREAD); - PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, child_name, loader_data); - if (probe != NULL) { - probe->remove_seen_thread(THREAD, PlaceholderTable::LOAD_SUPER); - } + MutexLocker mu(SystemDictionary_lock, THREAD); + placeholders()->find_and_remove(p_index, p_hash, child_name, loader_data, PlaceholderTable::LOAD_SUPER, THREAD); + SystemDictionary_lock->notify_all(); } if (HAS_PENDING_EXCEPTION || superk_h() == NULL) { // can null superk @@ -430,8 +430,8 @@ // We're using a No_Safepoint_Verifier to catch any place where we // might potentially do a GC at all. - // SystemDictionary::do_unloading() asserts that classes are only - // unloaded at a safepoint. + // Dictionary::do_unloading() asserts that classes in SD are only + // unloaded at a safepoint. Anonymous classes are not in SD. No_Safepoint_Verifier nosafepoint; dictionary()->add_protection_domain(d_index, d_hash, klass, loader_data, protection_domain, THREAD); @@ -486,7 +486,6 @@ // super class loading here. // This also is critical in cases where the original thread gets stalled // even in non-circularity situations. -// Note: only one thread can define the class, but multiple can resolve // Note: must call resolve_super_or_fail even if null super - // to force placeholder entry creation for this class for circularity detection // Caller must check for pending exception @@ -518,14 +517,6 @@ protection_domain, true, CHECK_(nh)); - // We don't redefine the class, so we just need to clean up if there - // was not an error (don't want to modify any system dictionary - // data structures). - { - MutexLocker mu(SystemDictionary_lock, THREAD); - placeholders()->find_and_remove(p_index, p_hash, name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); - } // parallelCapable class loaders do NOT wait for parallel superclass loads to complete // Serial class loaders and bootstrap classloader do wait for superclass loads @@ -595,6 +586,10 @@ // Do lookup to see if class already exist and the protection domain // has the right access + // This call uses find which checks protection domain already matches + // All subsequent calls use find_class, and set has_loaded_class so that + // before we return a result we call out to java to check for valid protection domain + // to allow returning the Klass* and add it to the pd_set if it is valid unsigned int d_hash = dictionary()->compute_hash(name, loader_data); int d_index = dictionary()->hash_to_index(d_hash); Klass* probe = dictionary()->find(d_index, d_hash, name, loader_data, @@ -652,7 +647,7 @@ } } - // If the class in is in the placeholder table, class loading is in progress + // If the class is in the placeholder table, class loading is in progress if (super_load_in_progress && havesupername==true) { k = SystemDictionary::handle_parallel_super_load(name, superclassname, class_loader, protection_domain, lockObject, THREAD); @@ -664,7 +659,9 @@ } } + bool throw_circularity_error = false; if (!class_has_been_loaded) { + bool load_instance_added = false; // add placeholder entry to record loading instance class // Five cases: @@ -690,7 +687,7 @@ // No performance benefit and no deadlock issues. // case 5. parallelCapable user level classloaders - without objectLocker // Allow parallel classloading of a class/classloader pair - bool throw_circularity_error = false; + { MutexLocker mu(SystemDictionary_lock, THREAD); if (class_loader.is_null() || !is_parallelCapable(class_loader)) { @@ -726,12 +723,13 @@ } } } - // All cases: add LOAD_INSTANCE + // All cases: add LOAD_INSTANCE holding SystemDictionary_lock // case 3: UnsyncloadClass || case 5: parallelCapable: allow competing threads to try // LOAD_INSTANCE in parallel - // add placeholder entry even if error - callers will remove on error + if (!throw_circularity_error && !class_has_been_loaded) { PlaceholderEntry* newprobe = placeholders()->find_and_add(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, NULL, THREAD); + load_instance_added = true; // For class loaders that do not acquire the classloader object lock, // if they did not catch another thread holding LOAD_INSTANCE, // need a check analogous to the acquire ObjectLocker/find_class @@ -740,19 +738,18 @@ // class loaders holding the ObjectLock shouldn't find the class here Klass* check = find_class(d_index, d_hash, name, loader_data); if (check != NULL) { - // Klass is already loaded, so just return it + // Klass is already loaded, so return it after checking/adding protection domain k = instanceKlassHandle(THREAD, check); class_has_been_loaded = true; - newprobe->remove_seen_thread(THREAD, PlaceholderTable::LOAD_INSTANCE); - placeholders()->find_and_remove(p_index, p_hash, name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); } } } + // must throw error outside of owning lock if (throw_circularity_error) { + assert(!HAS_PENDING_EXCEPTION && load_instance_added == false,"circularity error cleanup"); ResourceMark rm(THREAD); - THROW_MSG_0(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string()); + THROW_MSG_NULL(vmSymbols::java_lang_ClassCircularityError(), name->as_C_string()); } if (!class_has_been_loaded) { @@ -782,20 +779,6 @@ } } - // clean up placeholder entries for success or error - // This cleans up LOAD_INSTANCE entries - // It also cleans up LOAD_SUPER entries on errors from - // calling load_instance_class - { - MutexLocker mu(SystemDictionary_lock, THREAD); - PlaceholderEntry* probe = placeholders()->get_entry(p_index, p_hash, name, loader_data); - if (probe != NULL) { - probe->remove_seen_thread(THREAD, PlaceholderTable::LOAD_INSTANCE); - placeholders()->find_and_remove(p_index, p_hash, name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); - } - } - // If everything was OK (no exceptions, no null return value), and // class_loader is NOT the defining loader, do a little more bookkeeping. if (!HAS_PENDING_EXCEPTION && !k.is_null() && @@ -819,18 +802,22 @@ } } } - if (HAS_PENDING_EXCEPTION || k.is_null()) { - // On error, clean up placeholders - { - MutexLocker mu(SystemDictionary_lock, THREAD); - placeholders()->find_and_remove(p_index, p_hash, name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); - } - return NULL; - } + } // load_instance_class loop + + if (load_instance_added == true) { + // clean up placeholder entries for LOAD_INSTANCE success or error + // This brackets the SystemDictionary updates for both defining + // and initiating loaders + MutexLocker mu(SystemDictionary_lock, THREAD); + placeholders()->find_and_remove(p_index, p_hash, name, loader_data, PlaceholderTable::LOAD_INSTANCE, THREAD); + SystemDictionary_lock->notify_all(); } } + if (HAS_PENDING_EXCEPTION || k.is_null()) { + return NULL; + } + #ifdef ASSERT { ClassLoaderData* loader_data = k->class_loader_data(); @@ -850,8 +837,8 @@ // so we cannot allow GC to occur while we're holding this entry. // We're using a No_Safepoint_Verifier to catch any place where we // might potentially do a GC at all. - // SystemDictionary::do_unloading() asserts that classes are only - // unloaded at a safepoint. + // Dictionary::do_unloading() asserts that classes in SD are only + // unloaded at a safepoint. Anonymous classes are not in SD. No_Safepoint_Verifier nosafepoint; if (dictionary()->is_valid_protection_domain(d_index, d_hash, name, loader_data, @@ -898,8 +885,8 @@ // so we cannot allow GC to occur while we're holding this entry. // We're using a No_Safepoint_Verifier to catch any place where we // might potentially do a GC at all. - // SystemDictionary::do_unloading() asserts that classes are only - // unloaded at a safepoint. + // Dictionary::do_unloading() asserts that classes in SD are only + // unloaded at a safepoint. Anonymous classes are not in SD. No_Safepoint_Verifier nosafepoint; return dictionary()->find(d_index, d_hash, class_name, loader_data, protection_domain, THREAD); @@ -965,10 +952,6 @@ // throw potential ClassFormatErrors. // // Note: "name" is updated. - // Further note: a placeholder will be added for this class when - // super classes are loaded (resolve_super_or_fail). We expect this - // to be called for all classes but java.lang.Object; and we preload - // java.lang.Object through resolve_or_fail, not this path. instanceKlassHandle k = ClassFileParser(st).parseClassFile(class_name, loader_data, @@ -979,21 +962,6 @@ true, THREAD); - // We don't redefine the class, so we just need to clean up whether there - // was an error or not (don't want to modify any system dictionary - // data structures). - // Parsed name could be null if we threw an error before we got far - // enough along to parse it -- in that case, there is nothing to clean up. - if (parsed_name != NULL) { - unsigned int p_hash = placeholders()->compute_hash(parsed_name, - loader_data); - int p_index = placeholders()->hash_to_index(p_hash); - { - MutexLocker mu(SystemDictionary_lock, THREAD); - placeholders()->find_and_remove(p_index, p_hash, parsed_name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); - } - } if (host_klass.not_null() && k.not_null()) { assert(EnableInvokeDynamic, ""); @@ -1062,10 +1030,6 @@ // throw potential ClassFormatErrors. // // Note: "name" is updated. - // Further note: a placeholder will be added for this class when - // super classes are loaded (resolve_super_or_fail). We expect this - // to be called for all classes but java.lang.Object; and we preload - // java.lang.Object through resolve_or_fail, not this path. instanceKlassHandle k = ClassFileParser(st).parseClassFile(class_name, loader_data, @@ -1114,25 +1078,7 @@ } } - // If parsing the class file or define_instance_class failed, we - // need to remove the placeholder added on our behalf. But we - // must make sure parsed_name is valid first (it won't be if we had - // a format error before the class was parsed far enough to - // find the name). - if (HAS_PENDING_EXCEPTION && parsed_name != NULL) { - unsigned int p_hash = placeholders()->compute_hash(parsed_name, - loader_data); - int p_index = placeholders()->hash_to_index(p_hash); - { - MutexLocker mu(SystemDictionary_lock, THREAD); - placeholders()->find_and_remove(p_index, p_hash, parsed_name, loader_data, THREAD); - SystemDictionary_lock->notify_all(); - } - return NULL; - } - - // Make sure that we didn't leave a place holder in the - // SystemDictionary; this is only done on success + // Make sure we have an entry in the SystemDictionary on success debug_only( { if (!HAS_PENDING_EXCEPTION) { assert(parsed_name != NULL, "parsed_name is still null?"); @@ -1547,8 +1493,7 @@ // Other cases fall through, and may run into duplicate defines // caught by finding an entry in the SystemDictionary if ((UnsyncloadClass || is_parallelDefine(class_loader)) && (probe->instance_klass() != NULL)) { - probe->remove_seen_thread(THREAD, PlaceholderTable::DEFINE_CLASS); - placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, THREAD); + placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD); SystemDictionary_lock->notify_all(); #ifdef ASSERT Klass* check = find_class(d_index, d_hash, name_h, loader_data); @@ -1578,8 +1523,7 @@ probe->set_instance_klass(k()); } probe->set_definer(NULL); - probe->remove_seen_thread(THREAD, PlaceholderTable::DEFINE_CLASS); - placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, THREAD); + placeholders()->find_and_remove(p_index, p_hash, name_h, loader_data, PlaceholderTable::DEFINE_CLASS, THREAD); SystemDictionary_lock->notify_all(); } } @@ -1736,6 +1680,8 @@ } return newsize; } +// Assumes classes in the SystemDictionary are only unloaded at a safepoint +// Note: anonymous classes are not in the SD. bool SystemDictionary::do_unloading(BoolObjectClosure* is_alive) { // First, mark for unload all ClassLoaderData referencing a dead class loader. bool has_dead_loaders = ClassLoaderDataGraph::do_unloading(is_alive); @@ -2105,9 +2051,7 @@ // All loaded classes get a unique ID. TRACE_INIT_ID(k); - // Check for a placeholder. If there, remove it and make a - // new system dictionary entry. - placeholders()->find_and_remove(p_index, p_hash, name, loader_data, THREAD); + // Make a new system dictionary entry. Klass* sd_check = find_class(d_index, d_hash, name, loader_data); if (sd_check == NULL) { dictionary()->add_klass(name, loader_data, k); @@ -2116,12 +2060,8 @@ #ifdef ASSERT sd_check = find_class(d_index, d_hash, name, loader_data); assert (sd_check != NULL, "should have entry in system dictionary"); -// Changed to allow PH to remain to complete class circularity checking -// while only one thread can define a class at one time, multiple -// classes can resolve the superclass for a class at one time, -// and the placeholder is used to track that -// Symbol* ph_check = find_placeholder(name, class_loader); -// assert (ph_check == NULL, "should not have a placeholder entry"); + // Note: there may be a placeholder entry: for circularity testing + // or for parallel defines #endif SystemDictionary_lock->notify_all(); } diff -r fb364e5a0b34 -r 3916ac601e04 hotspot/src/share/vm/utilities/exceptions.hpp --- a/hotspot/src/share/vm/utilities/exceptions.hpp Wed Jan 09 12:10:25 2013 -0800 +++ b/hotspot/src/share/vm/utilities/exceptions.hpp Thu Jan 10 17:38:20 2013 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it @@ -267,6 +267,7 @@ #define THROW_WRAPPED_0(name, oop_to_wrap) THROW_WRAPPED_(name, oop_to_wrap, 0) #define THROW_ARG_0(name, signature, arg) THROW_ARG_(name, signature, arg, 0) #define THROW_MSG_CAUSE_0(name, message, cause) THROW_MSG_CAUSE_(name, message, cause, 0) +#define THROW_MSG_CAUSE_NULL(name, message, cause) THROW_MSG_CAUSE_(name, message, cause, NULL) #define THROW_NULL(name) THROW_(name, NULL) #define THROW_MSG_NULL(name, message) THROW_MSG_(name, message, NULL)