Round 3: RFR: 8013651 NMT: reserve/release sequence id's in incorrect order due to race

Zhengyu Gu zhengyu.gu at oracle.com
Tue Jun 11 13:05:07 PDT 2013 

Thanks Calvin!

-Zhengyu

On Jun 11, 2013, at 2:56 PM, Calvin Cheung wrote:

> I've reviewed it with Zhengyu offline.
> There are a few typos in the comment block (lines 638 - 678) in memTracker.cpp.
> He'll fix those typos before push.
> 
> thanks,
> Calvin
> 
> On 6/11/2013 8:00 AM, Zhengyu Gu wrote:
>> Hi,
>> 
>> I still need one full reviewer.
>> 
>> Thanks,
>> 
>> -Zhengyu
>> 
>> On Jun 11, 2013, at 8:33 AM, Zhengyu Gu wrote:
>> 
>>> I think it is in ClassPathZipEntry::open_stream() (src/share/vm/classfile/classLoader.cpp #243)
>>> 
>>> -Zhengyu
>>> 
>>> 
>>> On Jun 11, 2013, at 3:42 AM, David Holmes wrote:
>>> 
>>>> On 8/06/2013 12:55 AM, Zhengyu Gu wrote:
>>>>> On 6/6/2013 10:31 PM, David Holmes wrote:
>>>>>> I'm confused about the expectations of the constructor:
>>>>>> 
>>>>>> MemTracker::Tracker::Tracker(MemoryOperation op, Thread* thr)
>>>>>> 
>>>>>> Is thr, if not NULL, always the current thread? If so, then I don't
>>>>>> think it would be allocating from a SafepointSafe state; and if not
>>>>>> then it could change state immediately after you have checked it!
>>>>>> 
>>>>> Yes, thr is the current thread, and we actually do classloading in
>>>>> _thread_in_native state, following is the stack.
>>>>> 
>>>>> jvm.dll!MemTracker::Tracker::Tracker(MemTracker::Tracker::MemoryOperation op,
>>>>> Thread * thr)  Line 729    C++
>>>>>     jvm.dll!MemTracker::record_arena_size(unsigned char * addr,
>>>>> unsigned int size)  Line 344    C++
>>>>>     jvm.dll!Arena::set_size_in_bytes(unsigned int size)  Line 532 +
>>>>> 0xd bytes    C++
>>>>>     jvm.dll!Arena::grow(unsigned int x,
>>>>> AllocFailStrategy::AllocFailEnum alloc_failmode)  Line 570    C++
>>>>>     jvm.dll!Arena::Amalloc(unsigned int x,
>>>>> AllocFailStrategy::AllocFailEnum alloc_failmode)  Line 388 + 0x10
>>>>> bytes    C++
>>>>>     jvm.dll!ResourceArea::allocate_bytes(unsigned int size,
>>>>> AllocFailStrategy::AllocFailEnum alloc_failmode)  Line 71    C++
>>>>>     jvm.dll!resource_allocate_bytes(unsigned int size,
>>>>> AllocFailStrategy::AllocFailEnum alloc_failmode)  Line 39    C++
>>>>>     jvm.dll!ClassPathZipEntry::open_stream(const char * name)  Line
>>>>> 265 + 0xe bytes    C++
>>>>>     jvm.dll!LazyClassPathEntry::open_stream(const char * name) Line
>>>>> 323    C++
>>>>>     jvm.dll!ClassLoader::load_classfile(Symbol * h_name, Thread *
>>>>> __the_thread__)  Line 900 + 0x17 bytes    C++
>>>>>     jvm.dll!SystemDictionary::load_instance_class(Symbol * class_name,
>>>>> Handle class_loader, Thread * __the_thread__)  Line 1284 + 0x14 bytes
>>>>> C++
>>>>>     jvm.dll!SystemDictionary::resolve_instance_class_or_null(Symbol *
>>>>> name, Handle class_loader, Handle protection_domain, Thread *
>>>>> __the_thread__)  Line 769 + 0x18 bytes    C++
>>>>>     jvm.dll!SystemDictionary::resolve_or_null(Symbol * class_name,
>>>>> Handle class_loader, Handle protection_domain, Thread * __the_thread__)
>>>>> Line 227 + 0x15 bytes    C++
>>>>>     jvm.dll!SystemDictionary::resolve_or_fail(Symbol * class_name,
>>>>> Handle class_loader, Handle protection_domain, bool throw_error, Thread
>>>>> * __the_thread__)  Line 166 + 0x15 bytes    C++
>>>>>     jvm.dll!ConstantPool::klass_at_impl(constantPoolHandle this_oop,
>>>>> int which, Thread * __the_thread__)  Line 252 + 0x17 bytes    C++
>>>>>     jvm.dll!ConstantPool::klass_at(int which, Thread *
>>>>> __the_thread__)  Line 352 + 0x1b bytes    C++
>>>>>     jvm.dll!InterpreterRuntime::anewarray(JavaThread * thread,
>>>>> ConstantPool * pool, int index, int size)  Line 187 + 0x10 bytes C++
>>>>>     02ee6241()
>>>> So this is an IRT_ENTRY that puts us _thread_in_vm. Where does the transition to _thread_in_native occur in the subsequent frames?
>>>> 
>>>> David
>>>> -----
>>>> 
>>>>>     jvm.dll!JavaCalls::call_helper(JavaValue * result, methodHandle *
>>>>> m, JavaCallArguments * args, Thread * __the_thread__)  Line 402 + 0x36
>>>>> bytes    C++
>>>>>     jvm.dll!os::os_exception_wrapper(void (JavaValue *, methodHandle
>>>>> *, JavaCallArguments *, Thread *)* f, JavaValue * value, methodHandle *
>>>>> method, JavaCallArguments * args, Thread * thread)  Line 113 + 0x13
>>>>> bytes    C++
>>>>>     jvm.dll!JavaCalls::call(JavaValue * result, methodHandle method,
>>>>> JavaCallArguments * args, Thread * __the_thread__)  Line 307 + 0x1a
>>>>> bytes    C++
>>>>> jvm.dll!InstanceKlass::call_class_initializer_impl(instanceKlassHandle
>>>>> this_oop, Thread * __the_thread__)  Line 1125 + 0x1f bytes    C++
>>>>>     jvm.dll!InstanceKlass::call_class_initializer(Thread *
>>>>> __the_thread__)  Line 1093 + 0xd bytes    C++
>>>>>     jvm.dll!InstanceKlass::initialize_impl(instanceKlassHandle
>>>>> this_oop, Thread * __the_thread__)  Line 843    C++
>>>>>     jvm.dll!InstanceKlass::initialize(Thread * __the_thread__) Line
>>>>> 502 + 0xd bytes    C++
>>>>>     jvm.dll!initialize_class(Symbol * class_name, Thread *
>>>>> __the_thread__)  Line 973 + 0x20 bytes    C++
>>>>>     jvm.dll!Threads::create_vm(JavaVMInitArgs * args, bool *
>>>>> canTryAgain)  Line 3479 + 0xf bytes    C++
>>>>>     jvm.dll!JNI_CreateJavaVM(JavaVM_ * * vm, void * * penv, void *
>>>>> args)  Line 5113 + 0xd bytes    C++
>>>>>     java.exe!013713c1()
>>>>>     [Frames below may be incorrect and/or missing, no symbols loaded
>>>>> for java.exe]
>>>>>     java.exe!01371e78()
>>>>>     java.exe!0137cf67()
>>>>>     java.exe!0137ab83()
>>>>>     java.exe!0137cfa5()
>>>>>     java.exe!0137ac0d()
>>>>>     kernel32.dll!768b3677()
>>>>>     ntdll.dll!76fe9f42()
>>>>>     ntdll.dll!76fe9f15()
>>>>> 
>>>>> 
>>>>>> In memTracker.hpp for the !INCLUDE_NMT case class Tracker doesn't have
>>>>>> an allocation-type as a supertype. I'm also unclear whether the
>>>>>> methods that have:
>>>>>> 
>>>>>> return Tracker();
>>>>>> 
>>>>>> are going to be returning a stack-allocated object, or whether this
>>>>>> will actually force use of a copy-constructor at the call site. We
>>>>>> really want this to be a no-op (or as close as possible) when NMT is
>>>>>> not compiled in. Perhaps a static singleton instance of Tracker could
>>>>>> be used instead?
>>>>>> 
>>>>> Yes, static on can help solaris. Windows and Linux all optimize the copy
>>>>> constructor away.
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> -Zhengyu
>>>>> 
>>>>>> Thanks,
>>>>>> David
>>>>>> 
>>>>>> On 5/06/2013 12:26 AM, Zhengyu Gu wrote:
>>>>>>> Round 3:
>>>>>>> 
>>>>>>> Based on Coleen and Stefan's comment, reverted most of NMT tracking
>>>>>>> calls to original to reduce code changes.
>>>>>>> 
>>>>>>> http://cr.openjdk.java.net/~zgu/8013651/webrev.03/
>>>>>>> <http://cr.openjdk.java.net/%7Ezgu/8013651/webrev.03/>
>>>>>>> 
>>>>>>> 
>>>>>>> Tests:
>>>>>>>  JPRT
>>>>>>>  vm.quick.testlist on Linux 32
>>>>>>> 
>>>>>>> Thanks,
>>>>>>> 
>>>>>>> -Zhengyu
>>>>>>> 
>>>>>>> 
>>>>>>> On 5/22/2013 10:28 AM, Zhengyu Gu wrote:
>>>>>>>> Based on the discussion with Karen, Coleen and Harold, following
>>>>>>>> changes are made:
>>>>>>>> 
>>>>>>>> 1) Renamed NMTTrackOp to NMTTracker, avoid the confusion with VM
>>>>>>>> operations.
>>>>>>>> 2) Used NMTTracker's dtor to discard the tracking operation if no
>>>>>>>> recording is done.
>>>>>>>> 
>>>>>>>> Tests:
>>>>>>>> - JPRT
>>>>>>>> - vm.quick.testlist on Linux 32, Solaris sparcv9 and Windows 32.
>>>>>>>> 
>>>>>>>> Thanks,
>>>>>>>> 
>>>>>>>> -Zhengyu
>>>>>>>> 
>>>>>>>> 
>>>>>>>> On 5/14/2013 10:01 AM, Zhengyu Gu wrote:
>>>>>>>>> There can be race conditions between the memory operations and the
>>>>>>>>> book keeping records are written. For example, thread 1 releases a
>>>>>>>>> virtual memory block, before it can write the release record, thread
>>>>>>>>> 2 reserves the same virtual memory block and writes reservation
>>>>>>>>> first, as result, NMT indicates the block is "released".
>>>>>>>>> 
>>>>>>>>> The solution is that, for those operations that can cause the race
>>>>>>>>> conditions, NMT should pre-reserve sequence number for it, if the
>>>>>>>>> operation succeeds, NMT uses pre-reserved sequence number to write
>>>>>>>>> the record.
>>>>>>>>> 
>>>>>>>>> The tricky part is that, a sequence number is only good for the
>>>>>>>>> generation it is acquired, when there are reserved sequence number,
>>>>>>>>> NMT has to prevent itself from entering so called "sync-point" where
>>>>>>>>> the generation can be advanced.
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Bug: http://bugs.sun.com/view_bug.do?bug_id=8013651
>>>>>>>>> Webrev: http://cr.openjdk.java.net/~zgu/8013651/webrev/
>>>>>>>>> <http://cr.openjdk.java.net/%7Ezgu/8013651/webrev/>
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Tests:
>>>>>>>>>  1) JPRT
>>>>>>>>>  2) vm.quick.testlist on Linux 32, Linux x64 and Solaris Sparcv9
>>>>>>>>>  3) Kitchensink on Linux 32, Linux x64, Solaris Sparcv9 and Windows
>>>>>>>>> x64
>>>>>>>>>  4) NMT jtreg tests on Linux 32, Linux x64 and Solaris Sparcv9
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Thanks,
>>>>>>>>> 
>>>>>>>>> -Zhengyu
>

More information about the hotspot-runtime-dev mailing list