open-pipe deadlocked

[rixed]

Hello !

Sometime, my progam calls open-input-pipe and the forked child hangs
waiting for a lock (so after the fork but before executing the command).

So I read the code for open-process, especially what happens between the
fork and the execlp, and I noticed several potential problems :

- all ports are closed, but what about other open files that are not
  ports ? My application opens many files in C that are not known to
  guile. Shouldn't these be closed as well ?

- what if when forking some other guile thread hold one of the internal
  lock (for instance, the lock protecting the port table) ? Then the
  code between the fork and the exec (which loop on all ports, amongst
  other things) may try to grab this internal mutex, deadlocking.

Any thoughs?