[PyQt] random deadlocks in pyqt application

[Erik Janssens]

Hello Giovanni,

Thanks again for your assistance.  I believe I'm handling
these things correctly, also there is no use of python threads
in the application. I will reread those things to make
sure.

But we do use python's Queue module, do you think this
might cause issues ?  As far as I can see there is nothing
in the behaviour of the application that suggests this.

Regards,

Erik

> 
> ------------------------------
> 
> Message: 2
> Date: Mon, 31 Aug 2009 02:28:14 +0200
> From: Giovanni Bajo <rasky at develer.com>
> Subject: Re: [PyQt] random deadlocks in pyqt application
> To: erik.janssens at conceptive.be
> Cc: PyQT mailing list <pyqt at riverbankcomputing.com>
> Message-ID: <1251678494.4741.26.camel at ozzu>
> Content-Type: text/plain
> 
> On dom, 2009-08-30 at 11:22 +0200, Erik Janssens wrote:
> > Hi,
> > 
> > I'm having random deadlocks in my pyqt application (I don't do
> > any locking and such in the app itself, but the app has
> > 2 QThreads).
> > 
> > They appear to occur random when the application is used like
> > a madman (opening and closing windows all the time).  A strange
> > observation is that the chances for deadlock are higher when using
> > xvfb instead of the normal x display.  (I use this for running
> > unittests overnight)
> > 
> > I'm running Ubuntu 9.04 using python2.5 (the deadlocks also 
> > appear when using python2.6)
> > 
> > The first line in the stack trace is always :
> > 
> > "xcb_wait_for_reply () from /usr/lib/libxcb.so.1"
> > 
> > Has anybody seen this before or can give me a clue on how
> > to proceed with this issue ?
> 
> This exact segfault doesn't ring any bell to me, so I only have generic
> advices for you.
> 
> I saw many segfaults related to the fact that the QThreads are not being
> used in the way that they should:
> http://qt.nokia.com/doc/4.5/threads.html#threads-and-qobjects
> 
> Make sure that you are following all the advices in there.
> 
> Also, don't use Python's threading module if you're going to touch Qt's
> objects.