(XS) RFR: 8152849: share/vm/runtime/mutex.cpp:1161 assert(((uintptr_t(_owner))|(uintptr_t(_LockWord.FullWord))|(uintptr_t(_EntryList))|(uintptr_t(_WaitSet))|(uintptr_t(_OnDeck))) == 0) failed

[Daniel D. Daugherty]

On 8/17/16 6:04 PM, David Holmes wrote:
> Hi Dan,
>
> Thanks for looking at this.

No problem. I'm pretty sure I once chased the older version
of this bug... :-)


>
> On 17/08/2016 10:59 PM, Daniel D. Daugherty wrote:
>> On 8/17/16 1:45 AM, David Holmes wrote:
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8152849
>>>
>>> webrev: http://cr.openjdk.java.net/~dholmes/8152849/webrev/
>>
>> src/share/vm/runtime/mutex.cpp
>>     If the problem is a racy clearing of one of the fields, then the
>>     assert can still fire and the extra info might still show zeroes
>>     since they are two different queries of the fields.
>>
>>     For this diagnostic to be always accurate you need to save a copy
>>     of each field, assert() that all the copies or'ed together are == 0,
>>     and have the extra info printed from the copies.
>
> You are right of course. Don't know what I was thinking. :(
>
> http://cr.openjdk.java.net/~dholmes/8152849/webrev.v2/

src/share/vm/runtime/mutex.cpp
     No comments.

Thumbs up!

Dan



>
> Thanks,
> David
>
>> Dan
>>
>>
>>>
>>> This is a rare assertion failure that has proven to unreproducible
>>> even by directly trying to exercise the theoretical race conditions
>>> mentioned in the bug report. All I can do for now is augment the
>>> assert to print out the various values so we can at least see where
>>> things are failing, next time it happens.
>>>
>>> Example output:
>>>
>>> #  Internal Error
>>> (/scratch/dh198349/jdk9-hs/hotspot/src/share/vm/runtime/mutex.cpp:1157), 
>>>
>>> pid=21732, tid=21734
>>> #
>>> assert(((uintptr_t(_owner))|(uintptr_t(_LockWord.FullWord))|(uintptr_t(_EntryList))|(uintptr_t(_WaitSet))|(uintptr_t(_OnDeck))) 
>>>
>>> == 0) failed:
>>> _owner(0x0000000000000000)|_LockWord(0x0000000000000000)|_EntryList(0x0000000000000000)|_WaitSet(0x0000000000000000)|_OnDeck(0x00000000deaddead) 
>>>
>>> != 0
>>>
>>> Thanks,
>>> David
>>