Re: Callback deadlock

Matthew J. Francis wrote:

> Hi,
>
> I'm intermittently experiencing the attached deadlock in some Python code.
>
> As far as I can tell, the deadlock appears to be between a call to an 
> XTopWindowListener in thread 1 (the listener, also in Python code, 
> doesn't yet do anything more than print "I am here" on a callback) and 
> the main thread which is attempting to enumerate the paragraphs of a 
> text document in thread 2.
>
> Could anyone with more experience in UNO and locking matters help me to 
> understand what's going on here? If what I'm trying to do is essentially 
> not going to work, there is the alternative of busy-waiting for windows 
> to appear, but I'd like to avoid that if possible.

It is not completely clear if you are calling from a remote Python program, or from inside LO.
Assuming that it is remote, yes, there are problems with listeners in this situation. It can easily 
deadlock. I have posted a similar situation on this list some months ago, where I did a paragraph 
enumeration in a listener callback and it also deadlocked. See 
lists.freedesktop.org/archives/libreoffice/2015-April/067601.html

Basically the conclusion was the LO does too much locking here, but that it could not be avoided 
because of severe problems if it wouldn't lock.
-- 
Piet van Oostrum <piet@vanoostrum.org>
WWW: http://pietvanoostrum.com/
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