Re: Events

[Christoph Rohland]

Neil Brown <[e-mail]> writes:

> > No, that's not right (and would be _really_ happy to stand
> > corrected). select and signals for interruption are not
> > compatible. You always have a race condition between unblocking the
> > signal and actually getting into select. AFAIK POSIX defines the
> > pselect call for this problem which also introduces a signal mask
> > argument. Without this, signals are useless to interrupt select.
> 
> I hit just such a race in xdm with xdmcp enabled.  Because of the
> particular way I was using it (forcibly logging students in labs off by
> signalling xdm) I was caught by this race moderately often.
> 
> What I did was make the "struct timeval" which was passed to select a
> global, and had the signal handler set it to 0,0.  If the signal came
> in before the select, the select would exit immediately due to a
> timeout.

What a hack ;-)

Thanks for the idea
        		Christoph