RFR (XS) 8185160 -XX:DumpLoadedClassList omits graal classes

[Jiangli Zhou]

Hi Ioi,

> On Oct 19, 2017, at 10:55 AM, Ioi Lam <ioi.lam at oracle.com> wrote:
> 
> 
> 
> On 10/19/17 9:47 AM, Jiangli Zhou wrote:
>> 
>>> On Oct 18, 2017, at 9:50 PM, Ioi Lam <ioi.lam at oracle.com <mailto:ioi.lam at oracle.com>> wrote:
>>> 
>>> 
>>> 
>>> On 10/18/17 9:35 PM, Jiangli Zhou wrote:
>>>> Hi Ioi,
>>>> 
>>>>> On Oct 18, 2017, at 4:54 PM, Ioi Lam <ioi.lam at oracle.com <mailto:ioi.lam at oracle.com>> wrote:
>>>>> 
>>>>> 
>>>>> 
>>>>> On 10/17/17 9:04 PM, David Holmes wrote:
>>>>>> Hi Ioi,
>>>>>> 
>>>>>> On 18/10/2017 1:52 PM, Ioi Lam wrote:
>>>>>>> http://cr.openjdk.java.net/~iklam/jdk10/8185160-dump-class-list-omits-graal.v01/ <http://cr.openjdk.java.net/%7Eiklam/jdk10/8185160-dump-class-list-omits-graal.v01/> 
>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8185160 <https://bugs.openjdk.java.net/browse/JDK-8185160>
>>>>>>> 
>>>>>>> Summary:
>>>>>>> 
>>>>>>> DumpLoadedClassList skips classes that can't be stored into the CDS
>>>>>>> archive. For boot and platform loaders, only classes from the JRT image
>>>>>>> are listed.
>>>>>>> 
>>>>>>> The test for "is this class from JRT image" was insufficient. It
>>>>>>> checked only classes whose source ends with "...../modules". For the
>>>>>>> platform loader, which loads the graal classes, the source is in the
>>>>>>> form "jrt:/jdk.internal.vm.compiler".
>>>>>>> 
>>>>>>> The fix is to also check for a "jrt:" prefix.
>>>>>> 
>>>>>> So ./share/classfile/classLoader.hpp:
>>>>>> 
>>>>>> static bool is_jrt(const char* name) { return string_ends_with(name, MODULES_IMAGE_NAME); }
>>>>>> 
>>>>>> is a badly named function or just plain broken?
>>>>>> 
>>>>> 
>>>>> I've renamed all the is_jrt() functions to is_modules_image(), so it's clear as to what it does.
>>>>> 
>>>>> See http://cr.openjdk.java.net/~iklam/jdk10/8185160-dump-class-list-omits-graal.v02/ <http://cr.openjdk.java.net/%7Eiklam/jdk10/8185160-dump-class-list-omits-graal.v02/>
>>>> 
>>>> The logic looks puzzling. For both NULL class loader and the PlatformClassLoader:
>>>> 
>>>> The first if check at line 5938 excludes any classes not in the jimage.
>>>> 
>>>> 5938           if (!ClassLoader::is_modules_image(stream->source()) && strncmp(stream->source(), "jrt:", 4) != 0) {
>>>> 5939             skip = true;
>>>> 5940           }
>>>> The second if check at line 5942 skips any classes from the boot append class path loaded by the NULL class loader. The second check skips a subset of the classes that’s already skipped by the first check. The second check is redundant.
>>>> 
>>> You're right. The second check is redundant. I'll remove it.
>>> 
>>>> 5942           if (class_loader == NULL && ClassLoader::contains_append_entry(stream->source())) {
>>>> 5943             // For the boot loader, also skip all classes that are loaded from the appended entries
>>>> 5944             skip = true;
>>>> 5945           }
>>>> What about the classes from -Xbootclasspath/a (not in --patch-module and --upgrade-module-path)?
>>>> 
>>> I am not sure what you mean here.
>> 
>> This excludes all classes from the -Xbootclasspath/a. However, classes from -Xbootclasspath/a can be archived and used at runtime properly. 
>> 
> 
> Hi Jiangli,
> 
> You're right. I misunderstood the original comments about the treatment of the bootclasspath/a classes. Here's the updated code that should be easier to understand:
> 
>         bool skip = false;
>         if (class_loader == NULL || SystemDictionary::is_platform_class_loader(class_loader)) {
>           // For the boot and platform class loaders, skip classes that are not found in the
>           // java runtime image, such as those found in the --patch-module entries.
>           // These classes can't be loaded from the archive during runtime.
>           if (!ClassLoader::is_modules_image(stream->source()) && strncmp(stream->source(), "jrt:", 4) != 0) {
>             skip = true;
>           }
> 
>           if (class_loader == NULL && ClassLoader::contains_append_entry(stream->source())) {
>             // .. but don't skip the boot classes that are loaded from -Xbootclasspath/a
>             // as they can be loaded from the archive during runtime.
>             skip = false;
>           }
>         }

Can you please check with a exploded build if the above also works? What is the stream->source() from classes from exploded build loaded by the NULL loader and the PlatformClassLoader?

Thanks,
Jiangli

> 
> Thanks
> - Ioi
> 
> 
>> Thanks,
>> Jiangli
>> 
>>> 
>>> Thanks
>>> - Ioi
>>>> Thanks,
>>>> Jiangli
>>>> 
>>>>> 
>>>>> 
>>>>>>> I also restructured the code to make it easier to read -- the nesting of || and && is hard to follow.
>>>>>>> 
>>>>>>> The original code had a subtle bug with the "!" operator:
>>>>>>> 
>>>>>>> 5938   if (((class_loader == NULL && !ClassLoader::contains_append_entry(stream->source())) ||
>>>>>>> 5939 SystemDictionary::is_platform_class_loader(class_loader)) &&
>>>>>>> 5940       !ClassLoader::is_jrt(stream->source())) {
>>>>>>> 
>>>>>>> So if (class_loader == NULL && ClassLoader::contains_append_entry(stream->source()) was true,
>>>>>>> the class would NOT be skipped.
>>>>>>> 
>>>>>>> The new version removes the "!".
>>>>>> 
>>>>>> So there should be an updated test to trigger the original bug.
>>>>>> 
>>>>> 
>>>>> I added a test case, but it's in the closed repo for now (since the test case uses utilities in the closed AppCDS tests). This test will be opened as part of JDK-8185996
>>>>> 
>>>>> Thanks
>>>>> - Ioi
>>>>> 
>>>>>> Thanks,
>>>>>> David
>>>>>> 
>>>>>>> Thanks
>>>>>>> - Ioi
>>>>> 
>>>> 
>>> 
>> 
>