RFR(S): 7099824: G1: we should take the pending list lock before doing the remark pause

John Cuthbertson john.cuthbertson at oracle.com
Thu Oct 20 00:09:25 UTC 2011

Hi Ramki,

Thanks for the review. Do you think that waiting for the pending list 
lock will significantly delay cleanups? If so then adding an extra 
"needs_pll" flag to VM_CGC_Operation is an easy change.



On 10/19/11 16:50, Ramki Ramakrishna wrote:
> Hi John -- This looks good to me, although I didn't see any obvious 
> reason to make clean up pauses take the
> PLL lock given they do not mess with the pending list in any manner. 
> Otherwise looks good to me.
> -- ramki
> On 10/17/2011 2:36 PM, John Cuthbertson wrote:
>> Hi Everyone,
>> Can I have a couple of volunteers review these changes? The webrev 
>> can be found at: http://cr.openjdk.java.net/~johnc/7099824/wevrev.0/
>> Summary: During a G1 remark pause, the JVM may enqueue some 
>> discovered references on to the pending list. Whenever the JVM 
>> modifies the pending list, it is supposed to synchronize with the 
>> ReferenceHandler thread and acquire the pending list lock but G1's 
>> concurrent GC operations were not doing so.
>> Testing: the GC test suite with both CMS and G1, and jprt.
>> Thanks,
>> JohnC

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