[Haskell-cafe] debugging a hanging program: where to start?

[Aran Donohue]

Thanks folks! Forward progress is made...

Unfortunately, programs don't seem to write out their threadscope event logs
until they terminate, and mine hangs until I kill it, so I can't get at the
event log.

Tracing has taught me that before the hang-cause, my program splits its time
in pthread_cond_wait in two different threads, and select in a third. After
the hang, it no longer calls select and one of those pthread_cond_waits  in
the other. In the version without -threaded that doesn't hang, it never does
any pthread_cond_wait and never misses the select.

Now to go figure out what impossible condition it's waiting on, I guess.

Aran

On Thu, May 13, 2010 at 2:13 AM, Ketil Malde <ketil at malde.org> wrote:

> Aran Donohue <aran.donohue at gmail.com> writes:
>
> > I have a program that I can reliably cause to hang. It's concurrent using
> > STM, so I think it could be a deadlock or related issue. I also do some
> IO,
> > so I think it could be blocking in a system call.
>
> If it's the latter, 'strace' might help you.  Use 'strace -p PID' to
> attach to a running process.  Similarly, 'ltrace' can trace library
> calls (but probably less useful in this context?)
>
> (This is on Linux, but other OSes are likely to have similar tools.)
>
> -k
> --
> If I haven't seen further, it is by standing in the footprints of giants
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20100513/7fdbc579/attachment.html