2011/8/16 Andy Joslin <libvirt@bandjos.com>:

The documentation says something that concerns me: http://libvirt.org/html/libvirt-libvirt.html#virConnectClose       "It is possible for the last virConnectClose to return a positive value if some        other object still has a temporary reference to the connection,   but the        application should not try to further use a connection after the        virConnectClose that matches the initial open."

The application I am working on requires that I know when the last thread using this connection goes away, so I can properly cleanup some overhead.  If I can't trust the return value of this call, how will I know that the connection is indeed torn down? Under what circumstances will the virConnectClose behave this way?

Simplified example (omitting all error handling) that makes virConnectClose return 0: // opens a connection, ref count is 1 virConnectPtr conn = virConnectOpen("qemu:///system", 0); // gets domain 17, conn ref count is 2, because dom depends on conn virDomainPtr dom = virDomainLookupByID(conn, 17); ... // free dom, conn ref count is 1 again, because dom removes ref from conn virDomainFree(dom); // remove a ref from conn, ref count is 0, really close the connection, ret is 0 int ret = virConnectClose(conn); If the order of the last two calls is changed (it's totally okay to do this) than virConnectClose returns 1: ... // remove a ref from conn, ref count is 1, don't close the connection, ret is 1 int ret = virConnectClose(conn); // free dom, conn ref count is 0, really close the connection dom depended on virDomainFree(dom); There is no way yet (like a callback or something) libvirt could tell you when the connection is really closed in cases when virConnectClose returned > 0. You could achieve that virConnectClose is the one that really closes the connection when you ensure that all objects (domains, storage pools and volume, networks etc) obtained using that connection are freed before calling virConnectClose. Then virConnectClose will be the one that removes the last reference from the connection and closes it. -- Matthias Bolte http://photron.blogspot.com