Re: [Chicken-users] Race condition in scheduler.scm

[Elf]

On Sun, 17 Aug 2008, Jörg F. Wittenberger wrote:

> Hi all,
>
> in this message
> http://lists.gnu.org/archive/html/chicken-users/2008-08/msg00094.html
> I posted a patch to scheduler.scm, which fixes a race condition wrt. bad
> file descriptors in the waiting queue.
> (Attached is a slightly brushed up version.)
>
> I have not seen any replies to this message (which is sort of strange on
> this list).  Did anyone consider to roll it in?  If not, why?  Anything
> bad about it?
>
> The race originally arose in a somewhat strange setup, which might not
> be even repeatable for everyone, since it involved accidentally changing
> the scheduling sequence (using more or fewer exception handlers), which
> may have different results on different machines.
>
> But the issue as such is easy to recreate, if you make a thread wait
> asynchronously on any file descriptor and close that fd from a second
> thread.  (Something, which may or may not be intentional, but easy to
> do.)

i'm not understanding why this would cause a 'race condition', nor why your 
patch is necessary.  the lines which you deleted from the scheduler (the -1
check and forced-primordial) accomplish the same thing without raising an
exception or causing modifications to the signal/condition/exception handler
in unsafe ways.

-elf