Bug#650667: pthread_create fails with unknown signal
2011/12/1 Christoph Egger <firstname.lastname@example.org>:
> Jep exactly. All xulrunner and all webkit browsers started to crash when
> booting -9 instead of -8.
This can be time-consuming, but it most likely can give useful
information. I would try using svn-bisect against FreeBSD repository
to find the regression. Since unpatched kernel is unbuildable on GNU
userland, this would require an FreeBSD system with Debian