On Mon, Jun 23, 2025 at 12:02:31 +0100, Daniel P. Berrangé via Devel wrote: > From: Daniel P. Berrangé <berra...@redhat.com> > > The main XML parser code global initializer historically had a mutex > protecting it, and more recently uses a pthread_once. The RelaxNG > code, however, relies on three other global initializers that are > not thread safe, just relying on setting an integer "initialized" > flag. > > Calling the relevant initializers from libvirt in a protected global > initializer will protect libvirt's own concurrent usage, however, it > cannot protect against other libraries loaded in process that might > be using libxml2's schema code. Fortunately: > > * The chances of other loaded non-libvirt code using libxml is > relatively low > * The chances of other loaded non-libvirt code using the schema > validation / catalog functionality inside libxml is even > lower > * The chances of both libvirt and the non-libvirt usage having > their *1st* usage of libxml2 be concurrent is tiny
Additionaly IIUC this could be problem only when using the embedded driver mode as we don't use libxml2 in the exported API > IOW, in practice, although our solution doesn't fully fix the thread > safety, it is good enough. > > libxml2 should none the less still be fixed to make its global > initializers be thread safe without special actions by its API > consumers. > > Resolves: https://gitlab.com/libvirt/libvirt/-/issues/788 > Signed-off-by: Daniel P. Berrangé <berra...@redhat.com> > --- > src/util/virxml.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/src/util/virxml.c b/src/util/virxml.c > index 9d46e5f32f..c2d5a109dc 100644 > --- a/src/util/virxml.c > +++ b/src/util/virxml.c > @@ -26,6 +26,8 @@ > > #include <libxml/xmlsave.h> > #include <libxml/xpathInternals.h> > +#include <libxml/xmlschemastypes.h> > +#include <libxml/catalog.h> > > #include "virerror.h" > #include "virxml.h" > @@ -35,6 +37,7 @@ > #include "virstring.h" > #include "virutil.h" > #include "viruuid.h" > +#include "virthread.h" > #include "configmake.h" > > #define VIR_FROM_THIS VIR_FROM_XML > @@ -50,6 +53,25 @@ struct virParserData { > }; > > > +static int virXMLSchemaOnceInit(void) Please use the preferred style of return type on it's own line. > +{ > + if (xmlSchemaInitTypes() < 0) { > + virReportError(VIR_ERR_INTERNAL_ERROR, > + _("Unable to initialize libxml2 schema types")); > + return -1; > + } > + if (xmlRelaxNGInitTypes() < 0) { > + virReportError(VIR_ERR_INTERNAL_ERROR, > + _("Unable to initialize libxml2 RelaxNG data")); > + return -1; > + } > + /* No return value, it just ignores errors :-( */ > + xmlInitializeCatalog(); > + return 0; > +} > + > +VIR_ONCE_GLOBAL_INIT(virXMLSchema); > + > static xmlXPathContextPtr > virXMLXPathContextNew(xmlDocPtr xml) > { > @@ -1603,6 +1625,9 @@ virXMLValidatorInit(const char *schemafile) > { > g_autoptr(virXMLValidator) validator = NULL; > > + if (virXMLSchemaInitialize() < 0) > + return NULL; > + > validator = g_new0(virXMLValidator, 1); > > validator->schemafile = g_strdup(schemafile); > -- > 2.49.0 > Reviewed-by: Peter Krempa <pkre...@redhat.com>
