When creating qemu capabilities, a dummy virDomainObj is created just because our monitor code expects that. However, the object is created locked already. Then, under cleanup label, we simply unref the object which results in whole domain object to be disposed. The object lock is destroyed subsequently, but hey - it's still locked: ==24845== Thread #14's call to pthread_mutex_destroy failed ==24845== with error code 16 (EBUSY: Device or resource busy) ==24845== at 0x4C3024E: pthread_mutex_destroy (in /usr/lib64/valgrind/vgpreload_helgrind-amd64-linux.so) ==24845== by 0x531F72E: virMutexDestroy (virthread.c:83) ==24845== by 0x5302977: virObjectLockableDispose (virobject.c:237) ==24845== by 0x5302A89: virObjectUnref (virobject.c:265) ==24845== by 0x1DD37866: virQEMUCapsInitQMP (qemu_capabilities.c:3397) ==24845== by 0x1DD37CC6: virQEMUCapsNewForBinary (qemu_capabilities.c:3481) ==24845== by 0x1DD381E2: virQEMUCapsCacheLookup (qemu_capabilities.c:3609) ==24845== by 0x1DD30F8A: virQEMUCapsInitGuest (qemu_capabilities.c:744) ==24845== by 0x1DD31889: virQEMUCapsInit (qemu_capabilities.c:1020) ==24845== by 0x1DD7DD36: virQEMUDriverCreateCapabilities (qemu_conf.c:888) ==24845== by 0x1DDC57C0: qemuStateInitialize (qemu_driver.c:803) ==24845== by 0x53DC743: virStateInitialize (libvirt.c:777) ==24845== Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/qemu/qemu_capabilities.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c index 8193805..dce40e0 100644 --- a/src/qemu/qemu_capabilities.c +++ b/src/qemu/qemu_capabilities.c @@ -3394,7 +3394,10 @@ virQEMUCapsInitQMP(virQEMUCapsPtr qemuCaps, if (monpath) ignore_value(unlink(monpath)); VIR_FREE(monpath); - virObjectUnref(vm); + if (vm) { + virObjectUnlock(vm); + virObjectUnref(vm); + } virObjectUnref(xmlopt); if (pid != 0) { -- 2.0.5