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

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 wrote:

Aran Donohue 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