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The commit cb51aa48a777ddae6997faa9f28350cb62655ffd "Fix up connection reference counting." changed the driver closing and virConnectPtr unref-logic in virConnectClose(). Before this commit virConnectClose() closed all drivers of the given virConnectPtr and virUnrefConnect()'ed it afterwards. After this commit the driver-closing is done in virUnrefConnect() if and only if the ref-count of the virConnectPtr dropped to zero. This change in execution order leads to a virConnectPtr leak, at least for connections to Xen. The relevant call sequences: virConnectOpen() -> xenUnifiedOpen() ... ... xenInotifyOpen() -> virConnectRef(conn) ... xenStoreOpen() -> xenStoreAddWatch() -> conn->refs++ virConnectClose() -> xenUnifiedClose() ... ... xenInotifyClose() -> virUnrefConnect(conn) ... xenStoreClose() -> xenStoreRemoveWatch() -> virUnrefConnect(conn) Before the commit this additional virConnectRef/virUnrefConnect calls where no problem, because virConnectClose() closed the drivers explicitly and the additional refs added by the Xen subdrivers were removed properly. After the commit this additional refs result in a virConnectPtr leak (including a leak of the hypercall file handle; that's how I noticed this problem), because now the drivers are only close if and only if the ref-count drops to zero, but this cannot happen anymore, because the additional refs from the Xen subdrivers would only be removed if the drivers get closed, but that doesn't happen because the ref-count cannot drop to zero. The fix for this problem is simple: remove the virConnectRef/virUnrefConnect calls from the Xen subdrivers (see attached patch). Maybe someone could explain why the Xen Inotify and Xen Store driver do this extra ref-counting, but none of the other Xen subdrivers. It seems unnecessary to me and can be removed without problems. Signed-off-by: Chris Lalancette <clalance@redhat.com>
libvirt library code README
===========================
The directory provides the bulk of the libvirt codebase. Everything
except for the libvirtd daemon and client tools. The build uses a
large number of libtool convenience libraries - one for each child
directory, and then links them together for the final libvirt.so,
although some bits get linked directly to libvirtd daemon instead.
The files directly in this directory are supporting the public API
entry points & data structures.
There are two core shared modules to be aware of:
* util/ - a collection of shared APIs that can be used by any
code. This directory is always in the include path
for all things built
* conf/ - APIs for parsing / manipulating all the official XML
files used by the public API. This directory is only
in the include path for driver implementation modules
Then there are the hypervisor implementations:
* esx/ - VMware ESX and GSX support using vSphere API over SOAP
* lxc/ - Linux Native Containers
* opennebula/ - Open Nebula using XMLRPC
* openvz/ - OpenVZ containers using cli tools
* phyp/ - IBM Power Hypervisor using CLI tools over SSH
* qemu/ - QEMU / KVM using qemu CLI/monitor
* remote/ - Generic libvirt native RPC client
* test/ - A "mock" driver for testing
* uml/ - User Mode Linux
* vbox/ - Virtual Box using native API
* xen/ - Xen using hypercalls, XenD SEXPR & XenStore
Finally some secondary drivers that are shared for several HVs.
Currently these are used by LXC, OpenVZ, QEMU, UML and Xen drivers.
The ESX, OpenNebula, Power Hypervisor, Remote, Test & VirtualBox
drivers all implement the secondary drivers directly
* interface/ - Host network interface management
* network/ - Virtual NAT networking
* node_device/ - Host device enumeration
* secret/ - Secret management
* security/ - Mandatory access control drivers
* storage/ - Storage management drivers
Since both the hypervisor and secondary drivers can be built as
dlopen()able modules, it is *FORBIDDEN* to have build dependencies
between these directories. Drivers are only allowed to depend on
the public API, and the internal APIs in the util/ and conf/
directories