(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

[David Holmes]

Thanks Dan!

Still need a second reviewer please. It's really simple :)

David

On 19/08/2016 12:04 AM, Daniel D. Daugherty wrote:
> 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
>>>
>