RFR(M): 8069412 : Locks need better debug-printing support

[David Chase]

> In general I am fine with this changes. There are styles issues, indention (used 4 bytes instead of 2). Other then that I have only few comments.

markOop.cpp?  Fixed it.
LogCompilation files are java and 4-character indent by default.

> In vframe.cpp why you cloned print_locked_object_class_name() to all passes. Instead you could set Boolean local in inner scope if you want to print Verbose output after print_locked_object_class_name().

"mark" was not in scope outside, it seemed cleaner on balance just to clone the call.

> Also I don't think you need "_debug" in then name LockNode::is_nested_lock_region_debug().

I wanted it to be clear that this was only for debugging -- it is clone of the previous method with tracing in the failure paths.

> You only need to add additional check is_Lock() in debug mode where before we may only check jvms() != NULL. I think you simply can add explicit check in macro.cpp code:
> 
> !       // Not that preceding claim is documented anywhere else.
> !       if (alock->jvms() != NULL && alock->is_Lock()) {
> !         if (alock->as_Lock()->is_nested_lock_region()) {

I didn't change jvms() assignment -- for Unlock nodes there is a debug-only second field to hold this information,
because this is not the only place sensitive to which AbstractLock nodes have jvms() attached, and adding a jvms()
to Unlock nodes caused additional failures.  So the original condition still works.

thanks for the review,

David

> Thanks,
> Vladimir
> 
> On 2/12/15 7:09 PM, David Chase wrote:
>> http://cr.openjdk.java.net/~drchase/8069412/webrev.00/
>> 
>> This is the debugging support that I found very helpful to make progress on
>> https://bugs.openjdk.java.net/browse/JDK-8066576 "Lock still held"
>> 
>> It comes in three parts:
>> 
>> 1) When -XX:+Verbose, locks in stack backtrace are printed with additional information,
>> like so:
>> 
>> "FooThread" #19 daemon prio=10 os_prio=31 tid=0x00007fe41c2c8000 nid=0x6203 waiting for monitor entry [0x0000000110072000]
>>    java.lang.Thread.State: BLOCKED (on object monitor)
>>    JavaThread state: _thread_blocked
>> Thread: 0x00007fe41c2c8000  [0x6203] State: _at_safepoint _has_called_back 0 _at_poll_safepoint 0
>>    JavaThread state: _thread_blocked
>>    at foo.Foo.send(Foo.java:21)
>>    - waiting to lock <0x0000000780b89008> (a java.lang.Object)
>>      lockbits= locked(0x00007fe41c23d09a)->monitor={count=0x0000000000000001,waiters=0x0000000000000000,recursions=0x0000000000000000,owner=0x00007fe41b8fc000}
>>    at foo.Bar.bar(Bar.java:1)
>> 
>> The new line is the one beginning "     lockbits".
>> Without -XX:+Verbose, the old behavior remains.
>> 
>> 2) In a debug (#ifdef ASSERT) build, when -XX+:LogCompilation is specified,
>> additional records are written to the compilation log file describing which lock optimizations
>> are performed (and in some cases, which are not performed, and why).
>> 
>> For example:
>> 
>>   <eliminate_lock_set_nested lock='0' compile_id='1840' class_id='unlock' kind='?' stamp='350.736'>
>>   </eliminate_lock_set_nested>
>>   <eliminate_lock_set_nested lock='1' compile_id='1840' class_id='lock' kind='coarsened' stamp='350.736'>
>>   </eliminate_lock_set_nested>
>> 
>> where the first record indicates that a previously unoptimized lock (kind='?') was set to 'nested'
>> and the second record indicates that a previously coarsened lock was set to nested.
>> Other additional information recorded includes locations for Unlock nodes.
>> 
>> Even in release builds, the kind of elimination (nested, coarsened, non-escaping) is now noted.
>> 
>> 3) The compilation processing tool was enhanced to process these new records, producing output like this:
>> 
>> 1783 eliminate_lock_NOT_nested_lock_region ? lock  98.713 [@36 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_INLR_1 ? lock  98.713 [@36 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested ? unlock  98.713 [@-1 bar.BAR::setData (53 bytes), @54 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested ? lock  98.713 [@-1 bar.BAR::setData (53 bytes), @54 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested nested lock  98.713 [@-1 bar.BAR::setData (53 bytes), @54 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested ? unlock  98.713 [@-1 bar.BAR::getLength (5 bytes), @65 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested ? lock  98.713 [@-1 bar.BAR::getLength (5 bytes), @65 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_set_nested nested lock  98.713 [@-1 bar.BAR::getLength (5 bytes), @65 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_NOT_nested_lock_region ? lock  98.713 [@202 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock_INLR_1 ? lock  98.713 [@202 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock nested unlock  98.713 [@-1 bar.BAR::getLength (5 bytes), @65 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock nested lock  98.713 [@-1 bar.BAR::getLength (5 bytes), @65 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock nested unlock  98.714 [@-1 bar.BAR::setData (53 bytes), @54 foo.Foo::fooMethod (330 bytes)]
>> 1783 eliminate_lock nested lock  98.714 [@-1 bar.BAR::setData (53 bytes), @54 foo.Foo::fooMethod (330 bytes)]
>> 
>> This was tested running jtreg on compiler and runtime,
>> as well as many runs of the problematic application for 8066576,
>> plus JPRT of the hotspot testsuite,
>> plus built with XCode 4.6.3 and 6.1.1 on Mavericks and gcc 4.8.2 on Ubuntu 14.04.
>> 
>> David
>> 
>> 

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