[gambit-list] C stack frames need to be returned in exactly the same order they were created Re: FFI and threads: abrupt exit 71

Mikael mikael.rcv at gmail.com
Sat Feb 23 04:14:47 EST 2013


(From only looking very generally at your code,)

May this be a stack unwinding problem?

If you unwind a stack other than in the same order it was wound in the
first place, your Gambit process will terminate or at least crash.


You have a lambda A that invokes C-lambda B that invokes lambda C.

Also, a lambda D that invokes C-lambda E that invokes lambda F.

If you invoke A and A invokes B and B invokes C,

and then say, Gambit switches thread, and that Gambit thread invokes D
which invokes E which invokes F,

and then, say, Gambit switches thread again, and that Gambit thread returns
from C to B.

Then your Gambit process is toast.

To handle this you can switch off Gambit's threading system when you're in
B or E for the course of your C and F calls respectively. Note that
switching off Gambit's threading system means that some or several of
Gambit's built-in IO primitives would block forever.

See the "How to work with external libraries" Wiki page for how to switch
it off.

Was this of help?


2013/2/23 Dimitris Vyzovitis <vyzo at hackzen.org>

> I am running into an abrupt exit with error code 71 (OSError) when
> multiple (scheme) threads are making ffi calls that upcall to scheme.
> A simplified scenario (see attached file) is as follows:
> 2 or more threads make an ffi call.
> The ffi call is a longer running procedure, that makes upcalls into
> scheme procedures that do I/O.
> This results in the program exiting abruptly with error code 71, and
> no context information regarding the error (even when compiled and
> running with full debugging).
> For an illustration of the problem, see the attached file.
> The following should print dots indefinitely, but instead quickly
> terminates with 71.
> $ gsc exit71.scm
> $  gsi -e "(begin (load \"exit71\") (main))"
> ....<plenty of dots>.... $ echo $?
> 71
> This is with gambit-4.6.6, system is GNU/Linux x86-64.
> -- vyzo
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