vfork hangs

[Kip Macy]

I'm having problems with my python application hanging in vfork with
the child never completing the exec. It is hard for me to track it
down just by putting a break on vfork because the code is
multi-threaded, several thousand lines long, and doesn't hit this
right away. I saw it suggested that system is not thread safe on
solaris (the platform I'm using). The other thing of note is that a
SIGCLD is always received promptly before the vfork hang.