Re: [Condor-devel] condor and a threaded library

[Erik Paulson <epaulson@xxxxxxxxxxx>]

On Tue, Jan 29, 2008 at 09:18:05AM -0600, Matthew Farrellee wrote:
> Nick LeRoy wrote:
> > On Tue January 29 2008, Matthew Farrellee wrote:
> >> does anyone know of a current reason why a condor daemon could not be
> >> linked with a library that creates and manages its own threads? if so,
> >> what is it?
> > 
> > Most of Condor isn't thread safe -- we've made no effort to keep the code 
> > thread safe (lots of static data, etc).  If any of these threads interacts 
> > with Condor in any way, the results will likely be bad.  Similar to the 2nd 
> > commandment: "2 Thou shalt not follow the NULL pointer, for chaos and madness 
> > await thee at its end."
> 
> However, if the threads are confined to the library's code only?
> 

There's always the worry that we're calling some non-threadsafe C library
function that the library has properly protected but Condor hasn't. That
should be less and less of a worry as time goes on.

It's also usually the case that in order to do anything useful, somewhere in
that library you have to call back into the Condor code, and then all bets are
off. Non-reenterant Condor utility functions are all over the place, and
there are many places that hold state between calls to the same function.

We've been burned time and time again by threads on Windows, even though 
we were convinced that they don't interact with Condor code, and lo, it turns
out we still crash because of race condidtions. It just doesn't seem worth it.

What are you thinking about using?

-Erik