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Our RPC calls can be divided into two groups: regular and high priority. The latter can be then processed by so called high priority worker threads. This is our way of defeating a 'deadlock' and allowing some RPCs to be processed even when all (regular) worker threads are stuck. For instance: if all regular worker threads get stuck when talking to QEMU on monitor, the virDomainDestroy() can be processed by a high priority worker thread(s) and thus unstuck those threads. Now, this is all fine, except if users want to use virsh non interactively: virsh destroy $dom This does a bit more - it needs to open a connection. And that consists of multiple RPC calls: AUTH_LIST, CONNECT_SUPPORTS_FEATURE, CONNECT_OPEN, and finally CONNECT_REGISTER_CLOSE_CALLBACK. All of them are marked as high priority except the last one. Therefore, virsh just sits there with a partially open connection. There's one requirement for high priority calls though: they can not get stuck. Hopefully, the reason is obvious by now. And looking into the server side implementation the CONNECT_REGISTER_CLOSE_CALLBACK processing can't ever get stuck. The only driver that implements the callback for public API is Parallels (vz). And that can't block really. And for virConnectUnregisterCloseCallback() it's the same story. Therefore, both can be marked as high priority. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2143840 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General Public License, version 2.1 (or later). Some parts of the code that are not part of the C library may have the more restrictive GNU General Public License, version 2.0 (or later). See the files COPYING.LESSER and COPYING for full license terms & conditions.
Installation
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: