I'm seeing a very weird (and somewhat reproducable) crash in setSchedulerParameters. The backtrace looks like this: *** glibc detected *** python2.7: free(): invalid pointer: 0x000000000152bc48 *** ======= Backtrace: ========= /lib64/libc.so.6(+0x76166)[0x7faa9e991166] /usr/lib64/python2.7/site-packages/libvirtmod.so(virFree+0x29)[0x7faa9887bfe9] /lib/libvirt.so.0(virTypedParamsClear+0x54)[0x7faa98342fe4] /lib/libvirt.so.0(virTypedParamsFree+0x1e)[0x7faa9834302e] /usr/lib64/python2.7/site-packages/libvirtmod.so(+0x1b4dc)[0x7faa9886c4dc] /usr/lib64/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x5629)[0x7faa9f63a129] /usr/lib64/libpython2.7.so.1.0(PyEval_EvalFrameEx+0x68e8)[0x7faa9f63b3e8] /usr/lib64/libpython2.7.so.1.0(PyEval_EvalCodeEx+0x8ae)[0x7faa9f63bd5e] /usr/lib64/libpython2.7.so.1.0(PyEval_EvalCode+0x32)[0x7faa9f63be72] /usr/lib64/libpython2.7.so.1.0(+0xff25c)[0x7faa9f65625c] /usr/lib64/libpython2.7.so.1.0(PyRun_FileExFlags+0x90)[0x7faa9f656330] /usr/lib64/libpython2.7.so.1.0(PyRun_SimpleFileExFlags+0xef)[0x7faa9f6578cf] /usr/lib64/libpython2.7.so.1.0(Py_Main+0xc56)[0x7faa9f6693f6] /lib64/libc.so.6(__libc_start_main+0xfd)[0x7faa9e939d1d] python2.7[0x400649] I am using: Python2.7 Python-Libvirt 1.2.2 with the "[PATCH libvirt-python 1/2] setPyVirTypedParameter: Copy full field name" patch. Libvirt 1.2.1 A quick example: import libvirt for i in range(0,40): conn = libvirt.open(None) for domid in conn.listDomainsID(): dom = conn.lookupByID(domid) print dom.name() params = {} params['vcpu_period'] = 50000 params['vcpu_quota'] = 100000 dom.setSchedulerParameters(params) This will crash frequently (over 80% of the time), but not all the time. Interestingly, if I add 'dom = None' before 'conn = libvirt.open(None)', the crashes seem to stop. This is just a simple test case from my actual application though, so applying that workaround may be tough (and it seems like it shouldn't crash, even without that.