[libvirt] [PATCH v2 1/2] Allow for ff callbacks to be called by custom event implementations

The documentation says: And they did deadlock. In removeTimeout too. Now we supply a custom function to pick it from the opaque blob and fire. Signed-off-by: Wojtek Porczyk <woju(a)invisiblethingslab.com&gt; --- libvirt-override.c | 36 ++++++++++++------------------------ libvirt-override.py | 39 +++++++++++++++++++++++++++++++++++++++ sanitytest.py | 5 +++-- 3 files changed, 54 insertions(+), 26 deletions(-) diff --git a/libvirt-override.c b/libvirt-override.c index 9e40f00..37f7ee2 100644 --- a/libvirt-override.c +++ b/libvirt-override.c @@ -5223,6 +5223,9 @@ libvirt_virEventAddHandleFunc(int fd, VIR_PY_TUPLE_SET_GOTO(pyobj_args, 3, cb_args, cleanup); + /* If changing contents of the opaque object, please also change + * virEventExecuteFFCallback() in libvirt-override.py + */ VIR_PY_TUPLE_SET_GOTO(cb_args, 0, libvirt_virEventHandleCallbackWrap(cb), cleanup); VIR_PY_TUPLE_SET_GOTO(cb_args, 1, libvirt_virVoidPtrWrap(opaque), cleanup); VIR_PY_TUPLE_SET_GOTO(cb_args, 2, libvirt_virFreeCallbackWrap(ff), cleanup); @@ -5292,20 +5295,11 @@ libvirt_virEventRemoveHandleFunc(int watch) VIR_PY_TUPLE_SET_GOTO(pyobj_args, 0, libvirt_intWrap(watch), cleanup); result = PyEval_CallObject(removeHandleObj, pyobj_args); - if (!result) { + if (result) { + retval = 0; + } else { PyErr_Print(); PyErr_Clear(); - } else if (!PyTuple_Check(result) || PyTuple_Size(result) != 3) { - DEBUG("%s: %s must return opaque obj registered with %s" - "to avoid leaking libvirt memory\n", - __FUNCTION__, NAME(removeHandle), NAME(addHandle)); - } else { - opaque = PyTuple_GetItem(result, 1); - ff = PyTuple_GetItem(result, 2); - cff = PyvirFreeCallback_Get(ff); - if (cff) - (*cff)(PyvirVoidPtr_Get(opaque)); - retval = 0; } cleanup: @@ -5350,6 +5344,9 @@ libvirt_virEventAddTimeoutFunc(int timeout, VIR_PY_TUPLE_SET_GOTO(pyobj_args, 2, cb_args, cleanup); + /* If changing contents of the opaque object, please also change + * virEventExecuteFFCallback() in libvirt-override.py + */ VIR_PY_TUPLE_SET_GOTO(cb_args, 0, libvirt_virEventTimeoutCallbackWrap(cb), cleanup); VIR_PY_TUPLE_SET_GOTO(cb_args, 1, libvirt_virVoidPtrWrap(opaque), cleanup); VIR_PY_TUPLE_SET_GOTO(cb_args, 2, libvirt_virFreeCallbackWrap(ff), cleanup); @@ -5416,20 +5413,11 @@ libvirt_virEventRemoveTimeoutFunc(int timer) VIR_PY_TUPLE_SET_GOTO(pyobj_args, 0, libvirt_intWrap(timer), cleanup); result = PyEval_CallObject(removeTimeoutObj, pyobj_args); - if (!result) { + if (result) { + retval = 0; + } else { PyErr_Print(); PyErr_Clear(); - } else if (!PyTuple_Check(result) || PyTuple_Size(result) != 3) { - DEBUG("%s: %s must return opaque obj registered with %s" - "to avoid leaking libvirt memory\n", - __FUNCTION__, NAME(removeTimeout), NAME(addTimeout)); - } else { - opaque = PyTuple_GetItem(result, 1); - ff = PyTuple_GetItem(result, 2); - cff = PyvirFreeCallback_Get(ff); - if (cff) - (*cff)(PyvirVoidPtr_Get(opaque)); - retval = 0; } cleanup: diff --git a/libvirt-override.py b/libvirt-override.py index 63f8ecb..3d09d63 100644 --- a/libvirt-override.py +++ b/libvirt-override.py @@ -16,6 +16,7 @@ except ImportError: if str(cyg_e).count("No module named"): raise lib_e +import ctypes import types # The root of all libvirt errors. @@ -211,3 +212,41 @@ def virEventAddTimeout(timeout, cb, opaque): ret = libvirtmod.virEventAddTimeout(timeout, cbData) if ret == -1: raise libvirtError ('virEventAddTimeout() failed') return ret + + +# +# a caller for the ff callbacks for custom event loop implementations +# + +ctypes.pythonapi.PyCapsule_GetPointer.restype = ctypes.c_void_p +ctypes.pythonapi.PyCapsule_GetPointer.argtypes = ( + ctypes.py_object, ctypes.c_char_p) + +_virFreeCallback = ctypes.CFUNCTYPE(None, ctypes.c_void_p) + +def virEventExecuteFFCallback(opaque): + """ + Execute callback which frees the opaque buffer + + @opaque: the opaque object passed to addHandle or addTimeout + + WARNING: This function should not be called from any call by libvirt's + core. It will most probably cause deadlock in C-level libvirt code. + Instead it should be scheduled and called from implementation's stack. + + See https://libvirt.org/html/libvirt-libvirt-event.html#virEventAddHandleFunc + for more information. + + This function is not dependent on any event loop implementation. + """ + # The opaque object is really a 3-tuple, which contains a the real opaque + # pointer and the ff callback, both of which are inside PyCapsules. If not + # specified, the ff may be None. See libvirt-override.c. + + dummy, caps_opaque, caps_ff = opaque + ff = _virFreeCallback(ctypes.pythonapi.PyCapsule_GetPointer( + caps_ff, "virFreeCallback".encode("ascii"))) + if ff: + real_opaque = ctypes.pythonapi.PyCapsule_GetPointer( + caps_opaque, "void*".encode("ascii")) + ff(real_opaque) diff --git a/sanitytest.py b/sanitytest.py index a140ba2..6548831 100644 --- a/sanitytest.py +++ b/sanitytest.py @@ -345,11 +345,12 @@ for name in sorted(finalklassmap): # Phase 6: Validate that every python API has a corresponding C API for klass in gotfunctions: - if klass == "libvirtError": + if klass in ("libvirtError", "virEventAsyncIOImpl"): continue for func in sorted(gotfunctions[klass]): # These are pure python methods with no C APi - if func in ["connect", "getConnect", "domain", "getDomain"]: + if func in ["connect", "getConnect", "domain", "getDomain", + "virEventRegisterAsyncIOImpl"]: continue key = "%s.%s" % (klass, func) -- 2.5.5