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

2010/9/3 Daniel P. Berrange <berrange(a)redhat.com&gt;: > 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. >> >> I'm not sure how to fix that. > > Looking at the java code, I believe the problem is that the java > bindings are *not* using the threadsafe error APIs: > > In Connect.java > >    /** >     * call the error handling logic. Should be called after every libvirt call >     * >     * @throws LibvirtException >     */ >    protected void processError() throws LibvirtException { >        ErrorHandler.processError(libvirt, VCP); >    } > > Which calls into > >    public static void processError(Libvirt libvirt, ConnectionPointer conn) throws LibvirtException { >        virError vError = new virError(); >        int errorCode = libvirt.virConnCopyLastError(conn, vError); > > And virConnCopyLastError is *not* threadsafe: > > > /** >  * virConnCopyLastError: >  * @conn: pointer to the hypervisor connection >  * @to: target to receive the copy >  * >  * Copy the content of the last error caught on that connection >  * >  * This method is not protected against access from multiple >  * threads. In a multi-threaded application, always use the >  * global virGetLastError() API which is backed by thread >  * local storage. > > Regards, > Daniel Hm that might explain it, I'll check if that's the cause. Matthias