Thanks Andrew!
If you want more data points on failure modes, this and the linked
issues might be a rich source:
https://bugs.openjdk.java.net/browse/JDK-8184445
JShell is built on JDI and these various forms of intermittent attach
failures have been a continual pain point.
-Robert
On 6/10/19 1:30 AM, Andrew Leonard wrote:
Thanks for the feedback everyone.
Hi Alan, yes I can put some cycles into digging deeper with this one,
as you point out there's probably more that needs doing.
As Alex found running the new testcase 400 times it failed once still,
interestingly during initial startListening() rather than the accept()
where it was failing before.
On a general issue of "thread-safety", I had a good look through the
spec docs and architecture docs and couldn't find any specification of
thread-safety(or not), should it be inferred if the docs don't
specifically state "thread-safe" that it should be assumed as
"not-thread safe"?
Thanks
Andrew
Andrew Leonard
Java Runtimes Development
IBM Hursley
IBM United Kingdom Ltd
internet email: andrew_m_leon...@uk.ibm.com
From: Alan Bateman <alan.bate...@oracle.com>
To: "serguei.spit...@oracle.com" <serguei.spit...@oracle.com>, Andrew
Leonard <andrew_m_leon...@uk.ibm.com>,
serviceability-dev@openjdk.java.net
Date: 08/06/2019 10:12
Subject: Re: RFR JDK-8225474: JDI connector accept fails "Address
already in use" with concurrent listeners
------------------------------------------------------------------------
On 08/06/2019 05:53, serguei.spit...@oracle.com wrote:
> Hi Andrew,
>
> It looks good to me.
> Thank you for your investigation and taking care about this!
I think this one needs further analysis as changing listenMap to be a
CHM does not make this connector thread safe and doesn't address a
number of other places where the map is accessed without
synchronization. For example, startListening would need to be changed to
use `putIfAbsent`, stopListening would need to use `remove` rather than
get + remote. There are several others once you start looking at the
sub-classes, e.g. SocketListeningConnector.updateArgumentMapIfRequired.
At the API level, JDI does not require connectors to be thread safe. I
agree it is desirable for some of the connector implementations to be
thread safe, particularly ListeningConnectors as an obvious usage will
be for a listener thread to hand off a VirtualMachine to another thread.
Andrew - do you have cycles to investigate this further? I'm not opposed
to changing the map to be a CHM but I think it needs further work.
-Alan
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