ghc-6.8.1, +RTS -N2

[Johannes Waldmann]

what could be the reason for my program
(compiled with -threaded) crashing with +RTS -N2

it seems to work fine with "-N1".
I compiled with ghc-6.8.1 (installed from binary package).
I am using forkIO, some MVars, some IORefs, some Channels.

It seems  -prof -threaded does not work:
ghc-6.8.1: combination not supported: Threaded/Profiling

When I run the executable under gdb I get

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6afeb90 (LWP 7801)]
0x08138d8c in checkBlackHoles ()

This behaviour occurs both on a dual core PC
and on an single core hyperthreaded PC,
both running openSuse-10.3

I cannot tell whether this is an regression from 6.6
(I cannot easily backport my code).

Any hints appreciated, Johannes Waldmann.