RFR 8234613: JavaThread can escape back to Java from an ongoing handshake
Patricio Chilano
patricio.chilano.mateo at oracle.com
Sat Nov 23 00:45:35 UTC 2019
Thanks Coleen!
Patricio
On 11/22/19 5:15 PM, coleen.phillimore at oracle.com wrote:
>
> This fix looks good to me, from your explanations offline and in the
> bug report.
> Coleen
>
> On 11/22/19 1:25 PM, Patricio Chilano wrote:
>> Hi,
>>
>> This patch aims to address a current bug where, given the right
>> combination of handshakes and external suspend/resume, a JavaThread
>> can transition from a safe state back to Java without blocking for a
>> still-in-progress handshake. In the description of the bug I added an
>> example, tracing the state changes of the JavaThread as it goes
>> through the different transitions until it escapes the handshake.
>> Currently, the window of time for this issue to happen is so small
>> that we do not see actual failures running tests. Running test
>> SuspendAtExit.java and adding some small delay before restoring the
>> JavaThread state in java_suspend_self_with_safepoint_check() can
>> demonstrate the issue.
>> The proposed fix is to check again if we have a pending/in-progress
>> handshake operation after executing ~ThreadInVMForHandshake().
>>
>> Tested with mach5, tiers1-6 on all platforms (Linux, macOS, Windows
>> and Solaris).
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8234613
>> Webrev: http://cr.openjdk.java.net/~pchilanomate/8234613/v01/webrev/
>>
>> Thanks,
>> Patricio
>
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