[IPython-user] Re: [IPython-dev] A plea for help with a threading bug...

[Fernando Perez]

Prabhu Ramachandran wrote:
>>>>>>"YI" == Yariv Ido <yariv at vipe.technion.ac.il> writes:
> 
> 
>     YI> Hi, First of all, the segmentation fault is caused by some
>     YI> race condition.  Setting the TIMEOUT to 1 just increases the
>     YI> probability of that happening, so you could debug it more
>     YI> efficiently. If you would like to avoid setting it, try
>     YI> running ipython with the -gthread flag, and pressing 'tab'
>     YI> repeatedly...  More thoughts on the subject:
> 
> Well, I can't seem to reproduce this.  I even set TIMEOUT to 1.
> Debian, ipython-0.6.12_cvs (updated a week or two ago), pygtk-2.6.2.
> python-2.3.5.  

Did you try rapid-firing TAB many times?  It may take a few tries (it is a 
race condition, after all), but I've been able to consistently get the crash, 
on my Fedora3 box.  This is using python 2.3.4 though, I don't know if 2.3.5 
might perhaps have fixed the bug, esp. since Yariv seems to have tracked it 
down to readline.  In particular, I find this to be noteworthy from the 2.3.5 
release notes at http://www.python.org/2.3.5/NEWS.html:

Fixed broken threadstate swap in readline that could cause fatal errors when a 
readline hook was being invoked while a background thread was active. (SF bugs 
#660476 and #513033.)

This sounds remarkably similar to our situation.  If this is the case, then we 
have a closed case.  Yariv, do you have an easy way to test 2.3.5?  I can do 
it, but probably not today.

Thanks for the help tracking this down...

Best,

f