What were you trying to do that didn't work?

Calling

  virDomainDefineXMLFlags(c, xml, VIR_DOMAIN_DEFINE_VALIDATE);

concurrently from multiple threads leads to corruption of libxml2 state due to lack of thread safe global initialization.

What is the impact of this issue to you?

The libvirtd/virtqemud daemons sometimes need restarting after getting into the broken state.

Please provide the package NVR for which the bug is seen:

libvirt-libs-10.10.0-12.el9.x86_64

How reproducible is this bug?:

non-deterministic

Steps to reproduce

1.  Download badschema.c
2.  gcc -o badschema badschema.c -lvirt
3.  ./badschema

Expected results

No errors

Actual results

Varying errors, some % of the time

$ ./badschema 
libvirt: XML Util error : internal error: Unable to parse RelaxNG schema '/usr/share/libvirt/schemas/domain.rng': Error type 'string' is not exported by type library 'http://www.w3.org/2001/XMLSchema-datatypes'
$ ./badschema 
Relax-NG types library 'http://relaxng.org/ns/structure/1.0' already registered
$ ./badschema 
libvirt: XML Util error : internal error: Unable to parse RelaxNG schema '/usr/share/libvirt/schemas/domain.rng': Error type 'int' is not exported by type library 'http://www.w3.org/2001/XMLSchema-datatypes'
libvirt: XML Util error : internal error: Unable to parse RelaxNG schema '/usr/share/libvirt/schemas/domain.rng': Error type 'unsignedInt' is not exported by type library 'http://www.w3.org/2001/XMLSchema-datatypes'