[9] RFR (XS): 8139247: Improper locking of MethodData::_extra_data_lock

[Daniel D. Daugherty]

On 3/3/16 3:40 AM, Vladimir Ivanov wrote:
> http://cr.openjdk.java.net/~vlivanov/8139247/webrev.00

src/share/vm/ci/ciMethodData.cpp
     Nicely done!

We've been bitten by the "MutexLocker /*missing name*/ (lock);" before.
It's interesting that fixing that runs into JDK-8146616. We should
probably make an audit run on finding missing name instances (again).

Thumbs up!

Dan


> https://bugs.openjdk.java.net/browse/JDK-8139247
>
> Solaris Studio C++ compiler generates tightly coupled 
> Monitor::lock/unlock calls for unnamed MutexLocker which breaks 
> synchronization between ciMethodData::load_extra_data() and 
> MethodData::bci_to_extra_data().
>
>   MutexLocker(mdo->extra_data_lock());
>
> is compiled into:
>
>   load_extra_data+0x001d: movq %r13,%rdi
>   load_extra_data+0x0020: call lock [ 0xfffffd7fe6df46c0, .+0x7cc5c0 ]
>   load_extra_data+0x0025: movq %r13,%rdi
>   load_extra_data+0x0028: call unlock [ 0xfffffd7fe6df47f0, .+0x7cc6e8
>
> But after adding a name, we hit a compiler bug in SS12u4 and 
> Monitor::unlock call is missed. So, have to add a workaround (same as 
> in JDK-8146616 [1]).
>
> Testing: verified machine code for ciMethodData::load_extra_data().
>
> Best regards,
> Vladimir Ivanov
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8146616