线程：PyQt 崩溃 "unknown request in queue while dequeuing"
Threading: PyQt crashes with "unknown request in queue while dequeuing"
我正在开发的应用程序的一部分需要向一小群人发送一些电子邮件。由于连接到 SMTP 服务器并发送电子邮件可能需要一些时间，因此我想在此操作期间提供一个进度条，使用后台线程来完成这项工作。
现在发生的是，我可以实现一个工作正常的测试结构，但是一旦我尝试从我的应用程序的后端创建一个对象来实际执行任何电子邮件操作，它就会完全崩溃（因为尽管它有段错误），将其转储到控制台：
[xcb] Unknown request in queue while dequeuing
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
python: ../../src/xcb_io.c:179: dequeue_pending_request: Assertion `!xcb_xlib_unknown_req_in_deq' failed.
Aborted
我在搜索这些错误时发现的唯一相关线程说了一些关于信号实现错误的信息（对于 PySide，PySide and QProgressBar update in a different thread），但在我的情况下，信号工作完全正常，直到我尝试创建该对象（根本不基于 Qt classes）。
这是我的 GUI 代码的简化版本：
class SendingDialog(QtGui.QDialog):
def __init__(self, parent, optsDict, cls, zid):
QtGui.QDialog.__init__(self)
self.form = Ui_Dialog()
self.form.setupUi(self)
# initialize some class variables...
self.beginConnect()
self.thread = WorkerThread()
self.thread.insertOptions(self.opts, self.cls, self.zid)
self.thread.finished.connect(self.endOfThread)
self.thread.serverContacted.connect(self.startProgress)
self.thread.aboutToEmail.connect(self.updateProgress)
self.thread.start()
def beginConnect(self):
# start busy indicator
def startProgress(self):
# set up progress bar
def updateProgress(self):
# increment progress bar
def endOfThread(self):
self.thread.quit()
self.reject()
class WorkerThread(QtCore.QThread):
serverContacted = QtCore.pyqtSignal(name="serverContacted")
aboutToEmail = QtCore.pyqtSignal(name="aboutToEmail")
def insertOptions(self, opts, cls, zid):
self.opts = opts
self.cls = cls
self.zid = zid
def run(self):
# upon running the following line, the application crashes.
emailman = db.emailing.EmailManager(self.opts, self.cls, self.zid)
如果我将一些虚拟代码放入 run() 中，使其休眠、发出适当的信号或打印测试值，一切正常；但是一旦我尝试实例化 EmailManager，整个事情就会崩溃。
EmailManager是一个不起眼的class派生自object，取我给它的参数（opts是字典，cls是一种不同类型的同样不起眼的物体，zid 只是一个普通数字）。构造函数如下所示：
def __init__(self, optsDict, cls, zid):
self.opts = optsDict
self.cls = cls
self.historyItem = HistoryItem(zid)
self.studentsList = studentsInClass(cls)
self.connection = None
我正在根据参数构造其他几个对象，但除此之外，没有发生任何复杂或不寻常的事情。 db.emailing 模块中的代码根本没有使用 Qt 或线程。
我什至不知道如何开始调试它，因此非常感谢任何关于可能发生的事情或我如何尝试找出答案的建议。
编辑：如果它有帮助，这里是 gdb 的回溯（我对发生的事情了解不多，所以觉得它有用）：
Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffeb146700 (LWP 31150)]
0x00007ffff762acc9 in __GI_raise (sig=sig@entry=6)
at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0 0x00007ffff762acc9 in __GI_raise (sig=sig@entry=6)
at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007ffff762e0d8 in __GI_abort () at abort.c:89
#2 0x00007ffff7623b86 in __assert_fail_base (
fmt=0x7ffff7774830 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
assertion=assertion@entry=0x7ffff6a4420d "!xcb_xlib_unknown_req_in_deq", file=file@entry=0x7ffff6a441db "../../src/xcb_io.c", line=line@entry=179,
function=function@entry=0x7ffff6a446b0 "dequeue_pending_request")
at assert.c:92
#3 0x00007ffff7623c32 in __GI___assert_fail (
assertion=0x7ffff6a4420d "!xcb_xlib_unknown_req_in_deq",
file=0x7ffff6a441db "../../src/xcb_io.c", line=179,
function=0x7ffff6a446b0 "dequeue_pending_request") at assert.c:101
#4 0x00007ffff69d479c in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#5 0x00007ffff69d55c3 in _XReply ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#6 0x00007ffff69bc346 in XGetWindowProperty ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#7 0x00007ffff69bb22e in XGetWMHints ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#8 0x00007ffff4c87c4b in QWidgetPrivate::setWindowIcon_sys(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#9 0x00007ffff4c38405 in QWidget::create(unsigned long, bool, bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#10 0x00007ffff4c4086a in QWidget::setVisible(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#11 0x00007ffff509956e in QDialog::setVisible(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#12 0x00007ffff5c24b7c in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtGui.so
#13 0x00007ffff5099026 in QDialog::exec() ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#14 0x00007ffff5be5fb5 in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtGui.so
#15 0x000000000049968d in PyEval_EvalFrameEx ()
#16 0x00000000004a090c in PyEval_EvalCodeEx ()
#17 0x0000000000499a52 in PyEval_EvalFrameEx ()
#18 0x00000000004a1c9a in ?? ()
#19 0x00000000004dfe94 in ?? ()
#20 0x00000000004dc9cb in PyEval_CallObjectWithKeywords ()
#21 0x000000000043734b in PyErr_PrintEx ()
#22 0x00007ffff186fd4d in ?? ()
from /usr/lib/python2.7/dist-packages/sip.so
#23 0x00007ffff14b2ece in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtCore.so
#24 0x00007ffff45be32f in ?? ()
from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#25 0x00007ffff79c1182 in start_thread (arg=0x7fffeb146700)
at pthread_create.c:312
#26 0x00007ffff76ee47d in clone ()
at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
哇，这很晦涩。
X11 窗口函数显然不是线程安全的，除非明确设置为线程安全，并且出于某种原因 PyQt 不会自动将它们设置为线程安全。这可以通过在 QApplication 构造函数之前添加以下内容来纠正：
QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
请参阅 QApplicationAttributes 上的文档。
我正在开发的应用程序的一部分需要向一小群人发送一些电子邮件。由于连接到 SMTP 服务器并发送电子邮件可能需要一些时间，因此我想在此操作期间提供一个进度条，使用后台线程来完成这项工作。
现在发生的是，我可以实现一个工作正常的测试结构，但是一旦我尝试从我的应用程序的后端创建一个对象来实际执行任何电子邮件操作，它就会完全崩溃（因为尽管它有段错误），将其转储到控制台：
[xcb] Unknown request in queue while dequeuing
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
python: ../../src/xcb_io.c:179: dequeue_pending_request: Assertion `!xcb_xlib_unknown_req_in_deq' failed.
Aborted
我在搜索这些错误时发现的唯一相关线程说了一些关于信号实现错误的信息（对于 PySide，PySide and QProgressBar update in a different thread），但在我的情况下，信号工作完全正常，直到我尝试创建该对象（根本不基于 Qt classes）。
这是我的 GUI 代码的简化版本：
class SendingDialog(QtGui.QDialog):
def __init__(self, parent, optsDict, cls, zid):
QtGui.QDialog.__init__(self)
self.form = Ui_Dialog()
self.form.setupUi(self)
# initialize some class variables...
self.beginConnect()
self.thread = WorkerThread()
self.thread.insertOptions(self.opts, self.cls, self.zid)
self.thread.finished.connect(self.endOfThread)
self.thread.serverContacted.connect(self.startProgress)
self.thread.aboutToEmail.connect(self.updateProgress)
self.thread.start()
def beginConnect(self):
# start busy indicator
def startProgress(self):
# set up progress bar
def updateProgress(self):
# increment progress bar
def endOfThread(self):
self.thread.quit()
self.reject()
class WorkerThread(QtCore.QThread):
serverContacted = QtCore.pyqtSignal(name="serverContacted")
aboutToEmail = QtCore.pyqtSignal(name="aboutToEmail")
def insertOptions(self, opts, cls, zid):
self.opts = opts
self.cls = cls
self.zid = zid
def run(self):
# upon running the following line, the application crashes.
emailman = db.emailing.EmailManager(self.opts, self.cls, self.zid)
如果我将一些虚拟代码放入 run() 中，使其休眠、发出适当的信号或打印测试值，一切正常；但是一旦我尝试实例化 EmailManager，整个事情就会崩溃。
EmailManager是一个不起眼的class派生自object，取我给它的参数（opts是字典，cls是一种不同类型的同样不起眼的物体，zid 只是一个普通数字）。构造函数如下所示：
def __init__(self, optsDict, cls, zid):
self.opts = optsDict
self.cls = cls
self.historyItem = HistoryItem(zid)
self.studentsList = studentsInClass(cls)
self.connection = None
我正在根据参数构造其他几个对象，但除此之外，没有发生任何复杂或不寻常的事情。 db.emailing 模块中的代码根本没有使用 Qt 或线程。
我什至不知道如何开始调试它，因此非常感谢任何关于可能发生的事情或我如何尝试找出答案的建议。
编辑：如果它有帮助，这里是 gdb 的回溯（我对发生的事情了解不多，所以觉得它有用）：
Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffeb146700 (LWP 31150)]
0x00007ffff762acc9 in __GI_raise (sig=sig@entry=6)
at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0 0x00007ffff762acc9 in __GI_raise (sig=sig@entry=6)
at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007ffff762e0d8 in __GI_abort () at abort.c:89
#2 0x00007ffff7623b86 in __assert_fail_base (
fmt=0x7ffff7774830 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
assertion=assertion@entry=0x7ffff6a4420d "!xcb_xlib_unknown_req_in_deq", file=file@entry=0x7ffff6a441db "../../src/xcb_io.c", line=line@entry=179,
function=function@entry=0x7ffff6a446b0 "dequeue_pending_request")
at assert.c:92
#3 0x00007ffff7623c32 in __GI___assert_fail (
assertion=0x7ffff6a4420d "!xcb_xlib_unknown_req_in_deq",
file=0x7ffff6a441db "../../src/xcb_io.c", line=179,
function=0x7ffff6a446b0 "dequeue_pending_request") at assert.c:101
#4 0x00007ffff69d479c in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#5 0x00007ffff69d55c3 in _XReply ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#6 0x00007ffff69bc346 in XGetWindowProperty ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#7 0x00007ffff69bb22e in XGetWMHints ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#8 0x00007ffff4c87c4b in QWidgetPrivate::setWindowIcon_sys(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#9 0x00007ffff4c38405 in QWidget::create(unsigned long, bool, bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#10 0x00007ffff4c4086a in QWidget::setVisible(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#11 0x00007ffff509956e in QDialog::setVisible(bool) ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#12 0x00007ffff5c24b7c in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtGui.so
#13 0x00007ffff5099026 in QDialog::exec() ()
from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#14 0x00007ffff5be5fb5 in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtGui.so
#15 0x000000000049968d in PyEval_EvalFrameEx ()
#16 0x00000000004a090c in PyEval_EvalCodeEx ()
#17 0x0000000000499a52 in PyEval_EvalFrameEx ()
#18 0x00000000004a1c9a in ?? ()
#19 0x00000000004dfe94 in ?? ()
#20 0x00000000004dc9cb in PyEval_CallObjectWithKeywords ()
#21 0x000000000043734b in PyErr_PrintEx ()
#22 0x00007ffff186fd4d in ?? ()
from /usr/lib/python2.7/dist-packages/sip.so
#23 0x00007ffff14b2ece in ?? ()
from /usr/lib/python2.7/dist-packages/PyQt4/QtCore.so
#24 0x00007ffff45be32f in ?? ()
from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#25 0x00007ffff79c1182 in start_thread (arg=0x7fffeb146700)
at pthread_create.c:312
#26 0x00007ffff76ee47d in clone ()
at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
哇，这很晦涩。
X11 窗口函数显然不是线程安全的，除非明确设置为线程安全，并且出于某种原因 PyQt 不会自动将它们设置为线程安全。这可以通过在 QApplication 构造函数之前添加以下内容来纠正：
QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
请参阅 QApplicationAttributes 上的文档。