[libvirt-users] is libvirt java binding thread safe?

[Matthias Bolte]

2010/9/3 Daniel P. Berrange <berrange at redhat.com>:
> On Fri, Sep 03, 2010 at 01:02:09PM +0200, Matthias Bolte wrote:
>> Ah, okay, now I understand what you want to say.
>>
>> You have two threads A and B. When A runs on its own then it's just
>> fine, but when you add B (that triggers an exception on purpose and
>> ignores it) then A picks it up and reports it. This is the point where
>> thread safety comes to mind.
>>
>> libvirt stores errors in thread-local-storage. It uses
>> pthread_key_create/pthread_{get,set}specific for this (or
>> TlsAlloc/Tls{Get,Set}Value on Windows).
>>
>> I think what's happening here is that all your threads in Java share
>> the same thread-local-storage. Therefore, thread A can pickup the
>> error triggered by thread B, that should not happen.
>
> That could only happen if the JVM was using green threads instead of
> native threads, but no serious JVM still uses green threads these days.
>

Well, yes. That's what I thought too and that's why it took me a while
until I understood what he meant.

But I can reproduce it his test program and with latest libvirt and
libvirt-java and the default JVM here on Ubuntu 10.04:

$ java -version
java version "1.6.0_18"
OpenJDK Runtime Environment (IcedTea6 1.8.1) (6b18-1.8.1-0ubuntu1)
OpenJDK 64-Bit Server VM (build 16.0-b13, mixed mode)

I get stacktraces printed from TestMultiThreadingLibvirt for
exceptions that are actually triggered in
TestMultiThreadingLibvirtWithError in another thread.

Matthias