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@rutsky rutsky/MaterialTest.qml
Last active Aug 29, 2015

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PyQt 5.4.2 bug example: QSGMaterial::createShader() result object is destroyed before use + application hangs at exit
# PyQt 5.4.2 bug example: QSGMaterial::createShader() result object is destroyed
# before use + application hangs at exit
import textwrap
import sys
from PyQt5.QtQuick import (
QQuickItem, QSGMaterial,
QSGMaterialShader, QSGMaterialType,
QSGGeometry, QSGGeometryNode, QSGNode, QQuickView
)
from PyQt5.QtQml import (
qmlRegisterType, QQmlEngine, QQmlComponent, QQmlImageProviderBase,
QQmlProperty)
from PyQt5.QtCore import pyqtProperty, pyqtSignal, QUrl, QTimer
from PyQt5.QtWidgets import QApplication
class MyMaterialShader(QSGMaterialShader):
def __init__(self):
super().__init__()
self._matrix_uniform_id = None
print("MyMaterialShader() created")
def updateState(self, state, material, old_material):
if state.isMatrixDirty():
self.program().setUniformValue(
self._matrix_uniform_id, state.combinedMatrix())
if not isinstance(material, MyMaterial):
return
def attributeNames(self):
return ["qt_VertexPosition", "qt_VertexTexCoord"]
def initialize(self):
self._matrix_uniform_id = self.program().uniformLocation("qt_Matrix")
def vertexShader(self):
return textwrap.dedent("""\
uniform highp mat4 qt_Matrix;
attribute highp vec4 qt_VertexPosition;
attribute highp vec2 qt_VertexTexCoord;
varying highp vec2 qt_TexCoord;
void main()
{
qt_TexCoord = qt_VertexTexCoord;
gl_Position = qt_Matrix * qt_VertexPosition;
}
""")
def fragmentShader(self):
return textwrap.dedent("""\
varying highp vec2 qt_TexCoord;
void main()
{
gl_FragColor = vec4(qt_TexCoord.x, qt_TexCoord.y, 1, 1);
}
""")
def __del__(self):
print("MyMaterialShader() destroyed")
class MyMaterial(QSGMaterial):
_type = QSGMaterialType()
def __init__(self):
super().__init__()
def compare(self, other_material):
if self is other_material:
return 0
else:
return -1 if id(self) < id(other_material) else 1
def createShader(self):
shader = MyMaterialShader()
# Problem #1: created in Python QSGMaterialShader object is being
# destroyed when not referenced by Python.
# QSGMaterialShader's are cached inside Qt and rarely destroyed,
# so Qt fails with segfault when tries to use destroyed object.
# Workaround: store Python QSGMaterialShader objects indefinitely.
self._shader = shader # uncomment this for workaround
return shader
def type(self):
return self._type
class CustomShaderItem(QQuickItem):
def __init__(self):
super().__init__()
self.setFlag(QQuickItem.ItemHasContents, True)
def updatePaintNode(self, root_node, node_data):
print("Root node:", root_node)
if root_node is None:
root_node = QSGGeometryNode()
material = MyMaterial()
root_node.setMaterial(material)
root_node.setFlag(QSGNode.OwnsMaterial)
x = 0
y = 0
width = 100
height = 100
geometry = QSGGeometry(
QSGGeometry.defaultAttributes_TexturedPoint2D(),
5)
geometry.setDrawingMode(QSGGeometry.GL_TRIANGLE_STRIP)
root_node.setGeometry(geometry)
root_node.setFlag(QSGNode.OwnsGeometry)
vertices = geometry.vertexDataAsTexturedPoint2D()
vertices[0].set(x, y, 0, 0)
vertices[1].set(x + width, y, 1, 0)
vertices[2].set(x + width, y + height, 1, 1)
vertices[3].set(x, y + height, 0, 1)
vertices[4].set(x, y, 0, 0)
root_node.markDirty(QSGNode.DirtyGeometry)
root_node.markDirty(QSGNode.DirtyMaterial)
# According to documentation, lifetime of QSGNode is managed by Qt,
# so we cannot safely store it in Python.
# Transfer ownership to C++ to workaround this issue.
import sip
sip.transferto(root_node, root_node)
return root_node
def main():
app = QApplication(sys.argv)
qml_engine = QQmlEngine()
view = QQuickView(qml_engine, None)
scene_uri = QUrl.fromLocalFile("MaterialTest.qml")
view.setSource(scene_uri)
assert not view.errors()
shader_item = CustomShaderItem()
shader_item.setProperty("parent", view.rootObject())
view.show()
exit_code = app.exec_()
#print("Destroying QQuickView")
#del view
#print("QQuickView destroyed")
# Problem #2: destroying QQuickView that used Python-created QSGGeometryNode
# leads to deadlock.
#
# As I see, when QQuickView is being destroyed it waits until render thread
# clean ups all resources, which causes QSGGeometryNode to be destroyed,
# which asks to lock GIL, which is still locked by main thread.
#
# Here is stack traces at the moment of deadlock:
#
# (gdb) info threads
# Id Target Id Frame
# 4 Thread 0x7f705ca83700 (LWP 23802) "QXcbEventReader" 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# 3 Thread 0x7f7057df9700 (LWP 23803) "QQmlThread" 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# 2 Thread 0x7f7055aa7700 (LWP 23804) "QSGRenderThread" pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
# * 1 Thread 0x7f706bf21780 (LWP 23801) "python" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
# (gdb) bt
# #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
# #1 0x00007f706505e482 in QWaitConditionPrivate::wait (this=0x2cffb00, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:136
# #2 0x00007f706505e255 in QWaitCondition::wait (this=0x2cff538, mutex=0x2cff530, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:208
# #3 0x00007f70664b4527 in QSGThreadedRenderLoop::releaseResources (this=0x2a09600, w=0x27dcb80, inDestructor=true) at scenegraph/qsgthreadedrenderloop.cpp:1059
# #4 0x00007f70664b2ed8 in QSGThreadedRenderLoop::windowDestroyed (this=0x2a09600, window=0x2768670) at scenegraph/qsgthreadedrenderloop.cpp:825
# #5 0x00007f70664ad512 in QSGRenderLoop::cleanup () at scenegraph/qsgrenderloop.cpp:94
# #6 0x00007f70652d2c9e in qt_call_post_routines () at kernel/qcoreapplication.cpp:294
# #7 0x00007f705fdc6734 in QApplication::~QApplication (this=0x26c6ed0, __in_chrg=<optimized out>) at kernel/qapplication.cpp:808
# #8 0x00007f70607e5758 in sipQApplication::~sipQApplication (this=0x26c6ed0, __in_chrg=<optimized out>) at sipQtWidgetspart0.cpp:301912
# #9 0x00007f70607e5788 in sipQApplication::~sipQApplication (this=0x26c6ed0, __in_chrg=<optimized out>) at sipQtWidgetspart0.cpp:301915
# #10 0x00007f70607e8f21 in release_QApplication (sipCppV=0x26c6ed0) at sipQtWidgetspart0.cpp:303524
# #11 0x00007f70607e8fba in dealloc_QApplication (sipSelf=0x7f705fc42168) at sipQtWidgetspart0.cpp:303538
# #12 0x00007f7061cae346 in ?? () from /home/bob/work/proplan/env/lib/python3.4/site-packages/sip.so
# #13 0x00007f7061caf5e9 in ?? () from /home/bob/work/proplan/env/lib/python3.4/site-packages/sip.so
# #14 0x0000000000598732 in subtype_dealloc.lto_priv () at ../Objects/typeobject.c:1201
# #15 0x00000000004c88c7 in frame_dealloc.lto_priv () at ../Objects/frameobject.c:429
# #16 0x0000000000503dfb in fast_function (nk=<optimized out>, na=<optimized out>, n=0, pp_stack=0x7ffd401cf350, func=<optimized out>) at ../Python/ceval.c:4336
# #17 call_function (oparg=<optimized out>, pp_stack=0x7ffd401cf350) at ../Python/ceval.c:4262
# #18 PyEval_EvalFrameEx () at ../Python/ceval.c:2838
# #19 0x00000000005a9cb5 in PyEval_EvalCodeEx () at ../Python/ceval.c:3588
# Python Exception <class 'RuntimeError'> Type does not have a target.:
# Python Exception <class 'RuntimeError'> Type does not have a target.:
# #20 0x00000000005e7105 in PyEval_EvalCode (locals=, globals=, co=<code at remote 0x7f706bdf5420>) at ../Python/ceval.c:775
# #21 run_mod () at ../Python/pythonrun.c:2180
# #22 0x00000000005e71c9 in PyRun_FileExFlags () at ../Python/pythonrun.c:2133
# #23 0x00000000005e79aa in PyRun_SimpleFileExFlags () at ../Python/pythonrun.c:1606
# #24 0x00000000005fb69d in run_file (p_cf=<optimized out>, filename=<optimized out>, fp=<optimized out>) at ../Modules/main.c:319
# #25 Py_Main () at ../Modules/main.c:751
# #26 0x00000000004c2e7f in main () at ../Modules/python.c:69
# #27 0x00007f706b450ec5 in __libc_start_main (main=0x4c2da0 <main>, argc=2, argv=0x7ffd401cf7c8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd401cf7b8)
# at libc-start.c:287
# #28 0x00000000005b8db9 in _start ()
# (gdb) thread 2
# [Switching to thread 2 (Thread 0x7f7055aa7700 (LWP 23804))]
# #0 pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
# 238 ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S: No such file or directory.
# (gdb) bt
# #0 pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
# #1 0x00000000004ff96c in PyCOND_TIMEDWAIT (cond=<optimized out>, mut=<optimized out>, us=5000) at ../Python/condvar.h:103
# #2 take_gil.lto_priv () at ../Python/ceval_gil.h:224
# #3 0x00000000004ffb43 in PyEval_RestoreThread () at ../Python/ceval.c:448
# #4 0x00000000005e7c67 in PyGILState_Ensure () at ../Python/pystate.c:793
# #5 0x00007f7061cb6307 in ?? () from /home/bob/work/proplan/env/lib/python3.4/site-packages/sip.so
# #6 0x00007f7066888341 in sipQSGGeometryNode::~sipQSGGeometryNode (this=0x7f70480e6580, __in_chrg=<optimized out>) at sipQtQuickpart0.cpp:7733
# #7 0x00007f706688837c in sipQSGGeometryNode::~sipQSGGeometryNode (this=0x7f70480e6580, __in_chrg=<optimized out>) at sipQtQuickpart0.cpp:7734
# #8 0x00007f706646a178 in QSGNode::destroy (this=0x7f70480e6210) at scenegraph/coreapi/qsgnode.cpp:389
# #9 0x00007f706646a01d in QSGNode::~QSGNode (this=0x7f70480e6210, __in_chrg=<optimized out>) at scenegraph/coreapi/qsgnode.cpp:320
# #10 0x00007f706646a05c in QSGNode::~QSGNode (this=0x7f70480e6210, __in_chrg=<optimized out>) at scenegraph/coreapi/qsgnode.cpp:321
# #11 0x00007f706646a178 in QSGNode::destroy (this=0x7f70480e6080) at scenegraph/coreapi/qsgnode.cpp:389
# #12 0x00007f706646a01d in QSGNode::~QSGNode (this=0x7f70480e6080, __in_chrg=<optimized out>) at scenegraph/coreapi/qsgnode.cpp:320
# #13 0x00007f706646b49e in QSGTransformNode::~QSGTransformNode (this=0x7f70480e6080, __in_chrg=<optimized out>) at scenegraph/coreapi/qsgnode.cpp:1156
# #14 0x00007f706646b4ce in QSGTransformNode::~QSGTransformNode (this=0x7f70480e6080, __in_chrg=<optimized out>) at scenegraph/coreapi/qsgnode.cpp:1158
# #15 0x00007f70664efcb7 in QQuickWindowPrivate::cleanupNodesOnShutdown (item=0x273d390) at items/qquickwindow.cpp:2588
# #16 0x00007f70664effc4 in QQuickWindowPrivate::cleanupNodesOnShutdown (item=0x2d31f90) at items/qquickwindow.cpp:2616
# #17 0x00007f70664effc4 in QQuickWindowPrivate::cleanupNodesOnShutdown (item=0x2a052d0) at items/qquickwindow.cpp:2616
# #18 0x00007f70664f002b in QQuickWindowPrivate::cleanupNodesOnShutdown (this=0x2a057b0) at items/qquickwindow.cpp:2624
# #19 0x00007f70664b0df5 in QSGRenderThread::invalidateOpenGL (this=0x2cff4f0, window=0x2768670, inDestructor=true, fallback=0x2cff590) at scenegraph/qsgthreadedrenderloop.cpp:465
# #20 0x00007f70664b0520 in QSGRenderThread::event (this=0x2cff4f0, e=0x2cfd3f0) at scenegraph/qsgthreadedrenderloop.cpp:390
# #21 0x00007f70664b2078 in QSGRenderThread::processEventsAndWaitForMore (this=0x2cff4f0) at scenegraph/qsgthreadedrenderloop.cpp:644
# #22 0x00007f70664b23f3 in QSGRenderThread::run (this=0x2cff4f0) at scenegraph/qsgthreadedrenderloop.cpp:672
# #23 0x00007f706505cd9b in QThreadPrivate::start (arg=0x2cff4f0) at thread/qthread_unix.cpp:337
# #24 0x00007f706b7fc182 in start_thread (arg=0x7f7055aa7700) at pthread_create.c:312
# #25 0x00007f706b52947d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
# (gdb) thread 3
# [Switching to thread 3 (Thread 0x7f7057df9700 (LWP 23803))]
# #0 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# 81 ../sysdeps/unix/syscall-template.S: No such file or directory.
# (gdb) bt
# #0 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# #1 0x00007f7063bc0fe4 in g_main_context_poll (priority=2147483647, n_fds=1, fds=0x7f70500013e0, timeout=-1, context=0x7f70500009b0) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:4028
# #2 g_main_context_iterate (context=context@entry=0x7f70500009b0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3729
# #3 0x00007f7063bc10ec in g_main_context_iteration (context=0x7f70500009b0, may_block=1) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3795
# #4 0x00007f706534d149 in QEventDispatcherGlib::processEvents (this=0x7f70500008e0, flags=...) at kernel/qeventdispatcher_glib.cpp:418
# #5 0x00007f70652d0f1e in QEventLoop::processEvents (this=0x7f7057df8e10, flags=...) at kernel/qeventloop.cpp:128
# #6 0x00007f70652d11df in QEventLoop::exec (this=0x7f7057df8e10, flags=...) at kernel/qeventloop.cpp:204
# #7 0x00007f70650558e0 in QThread::exec (this=0x2732370) at thread/qthread.cpp:503
# #8 0x00007f706598c5c5 in QQmlThreadPrivate::run (this=0x2732370) at qml/ftw/qqmlthread.cpp:141
# #9 0x00007f706505cd9b in QThreadPrivate::start (arg=0x2732370) at thread/qthread_unix.cpp:337
# #10 0x00007f706b7fc182 in start_thread (arg=0x7f7057df9700) at pthread_create.c:312
# #11 0x00007f706b52947d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
# (gdb) thread 4
# [Switching to thread 4 (Thread 0x7f705ca83700 (LWP 23802))]
# #0 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# 81 in ../sysdeps/unix/syscall-template.S
# (gdb) bt
# #0 0x00007f706b51c12d in poll () at ../sysdeps/unix/syscall-template.S:81
# #1 0x00007f7067770b72 in poll (__timeout=-1, __nfds=1, __fds=0x7f705ca82d00) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
# #2 _xcb_conn_wait (c=c@entry=0x28a2c60, cond=cond@entry=0x28a2ca0, vector=vector@entry=0x0, count=count@entry=0x0) at ../../src/xcb_conn.c:447
# #3 0x00007f706777264f in xcb_wait_for_event (c=0x28a2c60) at ../../src/xcb_in.c:622
# #4 0x00007f705fb3df81 in QXcbEventReader::run (this=0x28b0b90) at qxcbconnection.cpp:1105
# #5 0x00007f706505cd9b in QThreadPrivate::start (arg=0x28b0b90) at thread/qthread_unix.cpp:337
# #6 0x00007f706b7fc182 in start_thread (arg=0x7f705ca83700) at pthread_create.c:312
# #7 0x00007f706b52947d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
#
# (This issue is not reproduces in Windows, since Qt 5.4 still uses single
# threaded rendering there.)
return exit_code
if __name__ == "__main__":
exit_code = main()
sys.exit(exit_code)
import QtQuick 2.0
Item {
}
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