RFR(S) 8176363: Incorrect lock order for G1 PtrQueue related locks (original) (raw)

Mikael Gerdin mikael.gerdin at oracle.com
Thu Mar 9 15:52:10 UTC 2017

Hi Thomas,

On 2017-03-09 10:42, Thomas Schatzl wrote:

Hi Mikael,

On Wed, 2017-03-08 at 15:16 +0100, Mikael Gerdin wrote: Hi all,

Please review this change to the lock rank of the locks taken in the G1 pre and post write barriers. The rank of these locks have long been a problem since even though they are leaf locks semantically they have been ranked as "nonleaf" locks in the lock rank system and this has caused several issues over the years where a thread holding a VM mutex and attempting to write an oop would in some rare cases hit a deadlock warning due to it acquiring one of the CBL monitors. Now this problem has come up yet again with the weak JNI handles bugfix where a lock rank assertion was hit yet again due to the fact that some code was holding a leaf lock while resolving a weak JNI handle. I suggest that the ranks of the involved locks are changed to "leaf - 1", allowing them to be acquired by threads holding "leaf" locks. Looks good to me.

Thanks for the review.

/Mikael

Thomas

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