[Haskell-cafe] GHC RTS bug: segmentation fault

[Manlio Perillo]

Hi.

In a program I have experienced a segmentation fault;
not only that but also:

* tpp.c:63: __pthread_tpp_change_priority: Assertion `new_prio == -1 || 
(new_prio >= __sched_fifo_min_prio && new_prio <= 
__sched_fifo_max_prio)' failed.

* internal error: removeThreadFromQueue: not found
     (GHC version 6.8.2 for i386_unknown_linux)
     Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug


I have managed to write a program that reproduces the problem:
http://hpaste.org/fastcgi/hpaste.fcgi/view?id=3714

Compile with: $ghc --make -threaded -O2 main.hs
Execute with: $./main +RTS -A128M -s -c -N4 -RTS 5000000 500

This should produce a segmentation fault (or one of the previous errors).

I strongly suspect that the cause is an uncaught stack overflow.

Executing the code with only 1 threads, there are no more problems.
Increasing the thread stack size (-k1M), there are no more problems.


If the problem is really an uncaught stack overflow, I'm rather sure 
that a more simple test can be written, to reproduce the problem.

I'm on Linux Debian Etch i386; GHC 6.8.2.


Some notes about the program:
- when no segmentation fault occurs, the program requires about 1 GB of
   memory
- there is no real parallelization, only 1 CPU is used
- the mapReduce implementation is taken from Real World Haskell
- the code is adapted from the code I'm using in a project


Thanks  Manlio Perillo