[15] RFR: 8246381: VM crashes with "Current BasicObjectLock* below than low_mark"

Jamsheed C M jamsheed.c.m at oracle.com
Wed Jul 15 22:16:11 UTC 2020

(Thank you Dean, adding serviceability team as this issue involves JVMTI 
features PopFrame, EarlyReturn features)

JBS entry: https://bugs.openjdk.java.net/browse/JDK-8246381

(testing: mach5, tier1-5 links in JBS)

Best regards,


On 15/07/2020 21:25, Jamsheed C M wrote:
> Hi,
> Async handling at method entry requires it to be aware of 
> synchronization(like whether it is doing async handling before lock 
> acquire or after)
> This is required as exception handler rely on this info for 
> unlocking.  Async handling code never had this special condition 
> handled and it worked most of the time as we were using biased locking 
> which got disabled by [1]
> There was one other issue reported in similar time[2]. This issue got 
> triggered in test case by [3], back to back extra safepoint after 
> suspend and TLH for ThreadDeath. So in this setup both PopFrame 
> request and Thread.Stop request happened together for the test 
> scenario and it reached java method entry with pending_exception set.
> I have done a partial fix for the issue, mainly to handle production 
> mode crash failures(do not unlock flag related ones)
> Fix detail:
> 1) I save restore the "do not unlock" flag in async handling.
> 2) Return for floating pending exception for some cases(PopFrame, 
> Early return related). This is debug(JVMTI) feature and floating 
> exception can get cleaned just like that in present compiler request 
> and deopt code.
> webrev :http://cr.openjdk.java.net/~jcm/8246381/webrev.02/
> There are more problems in these code areas, like we clear all 
> exceptions in compilation request path(interpreter,c1), as well as 
> deoptimization path.
> All these un-handled cases will be separately handled by 
> https://bugs.openjdk.java.net/browse/JDK-8249451
> Request for review.
> Best regards,
> Jamsheed
> [1]https://bugs.openjdk.java.net/browse/JDK-8231264 
> <https://bugs.openjdk.java.net/browse/JDK-8231264>
> [2] https://bugs.openjdk.java.net/browse/JDK-8246727
> [3] https://bugs.openjdk.java.net/browse/JDK-8221207

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