defender methods analysis, classloading and java.lang.StackOverflowError

[Keith McGuigan]

Hi Sergey -

BTW, I'm not sure if GCC has any fault in this situation -- the way it's 
currently coded, we need to have size in parseClassFile()'s frame for 
the entirety of the GenericAnalyzer object.  And since parseClassFile() 
calls itself recursively....

I suspect replacing the stack-allocation with resource-allocation would 
resolve the problem too:

{
GenericAnalyzer* ga = new GenericAnalyzer(...);
ga->run(...)
}

... because then we'll use less room in parseClassFile()'s stack.  But I 
don't think that's going to explain the ~8K/frame difference you're 
seeing.  That's probably coming from within the GenericAnalyzer itself 
(which does use recursion too).

--
- Keith

On 3/14/2012 11:17 AM, Sergey Kuksenko wrote:
> On 03/14/2012 07:08 PM, Sergey Kuksenko wrote:
>> Hi All,
>>
>> It is not a big secret that HotSpot do classloading of
>> superclasses/superinterfaces recursively.
>> That means - for any fixed stack size there is classes/interfaces
>> chain which causes java.lang.StackOverflowError
>> For example, on Linux x86-32, chain of 512 interfaces needs at least
>> 2.5Megabytes stack size using jdk7u2 (default stack size == 320k).
>> Maybe it is not a good idea to do classloading with recursion, but it
>> is a topic for another mail list.
>>
>> Let's back to defenders.
>> I was playing with interface chains. All interfaces (except the first)
>> are empty. There are no defender methods here.
>> As result I've got on Linux x86-32:
>> - jdk7u2 requires ~4.8K per interface
>> - jdk8 requires ~5K per interface
>> - lambda build requires ~13K per interface.
>>
>> Lambda's HotSpot requires 2.5 larger stack size settings than jdk8.
>> This is really significant change. Jdk7 & 8 with default stack size
>> (Linux32) may load chain of ~60 classes/interfaces, but lambda may
>> load chain only of ~20 classes/interfaces. The source of that is
>> declaration "GenericAnalyzer ga;" in the
>> "ClassFileParser::parseClassFile" method and it doesn't matter that
>> the declaration is inside never executed scope/block.
>> We may say "thank you" to gcc. I didn't check, but expecting the
>> similar problem for other C++ compilers and platforms.
>>
>> I've attached patch which solves that problem. Simple extracting
>> couple lines of code into separate method bring back lambda to jdk8
>> stack size requirements.
>>
>
> It looks like I lost the attachment, trying to repeat.
>
>
> ------------------------------
> diff -r 108d1e7220ee src/share/vm/classfile/classFileParser.cpp
> --- a/src/share/vm/classfile/classFileParser.cpp Thu Feb 02 01:53:12
> 2012 -0500
> +++ b/src/share/vm/classfile/classFileParser.cpp Tue Mar 13 19:24:51
> 2012 +0400
> @@ -3396,13 +3396,9 @@
> #endif
>
> if (has_default_methods && !access_flags.is_interface()) {
> - ResourceMark rm(THREAD);
> -
> - GenericAnalyzer ga;
> - ga.run(
> - class_name, this_klass, super_klass, &all_mirandas,
> - methods, methods_annotations, methods_parameter_annotations,
> - methods_default_annotations, CHECK_(nullHandle));
> + analyze_defaults(class_name, this_klass, super_klass, &all_mirandas,
> + methods, methods_annotations, methods_parameter_annotations,
> + methods_default_annotations, CHECK_(nullHandle));
> }
>
> // Miranda methods
> @@ -3523,6 +3519,22 @@
> return this_klass;
> }
>
> +void ClassFileParser::analyze_defaults(
> + Symbol* class_name, instanceKlassHandle klass,
> + instanceKlassHandle super, GrowableArray<methodOop>* mirandas,
> + objArrayHandle methods, objArrayHandle annotations,
> + objArrayHandle annot_params, objArrayHandle annot_defaults, TRAPS){
> +
> + ResourceMark rm(THREAD);
> +
> + GenericAnalyzer ga;
> + ga.run(
> + class_name, klass, super, mirandas,
> + methods, annotations, annot_params,
> + annot_defaults, THREAD);
> +
> +}
> +
>
> unsigned int
> ClassFileParser::compute_oop_map_count(instanceKlassHandle super,
> diff -r 108d1e7220ee src/share/vm/classfile/classFileParser.hpp
> --- a/src/share/vm/classfile/classFileParser.hpp Thu Feb 02 01:53:12
> 2012 -0500
> +++ b/src/share/vm/classfile/classFileParser.hpp Tue Mar 13 19:24:51
> 2012 +0400
> @@ -139,6 +139,12 @@
> void parse_classfile_signature_attribute(constantPoolHandle cp,
> instanceKlassHandle k, TRAPS);
> void parse_classfile_bootstrap_methods_attribute(constantPoolHandle cp,
> instanceKlassHandle k, u4 attribute_length, TRAPS);
>
> + void analyze_defaults(
> + Symbol* class_name, instanceKlassHandle klass,
> + instanceKlassHandle super, GrowableArray<methodOop>* mirandas,
> + objArrayHandle methods, objArrayHandle annotations,
> + objArrayHandle annot_params, objArrayHandle annot_defaults, TRAPS);
> +
> // Annotations handling
> typeArrayHandle assemble_annotations(u1* runtime_visible_annotations,
> int runtime_visible_annotations_length,
>
>
>
>