timer_create

[Simon Marlow]

Christian Maeder wrote:
> Ian Lynagh wrote:

>> I'm not sure why we have both HAVE_TIMER_CREATE and USE_TIMER_CREATE.
> 
> I'd like to know, too.

It's because the configure script checks for more than just the 
existence of timer_create() (HAVE_TIMER_CREATE), it checks that it works 
well enough to use (USE_TIMER_CREATE).  Historical versions of Linux had 
broken implementations of timer_create() that we need to avoid. 
Unfortunately this means that taking a GHC binary built on a newer Linux 
will not work on an older version.

timer_create() is needed so that we can avoid needing to use the SIGALRM 
signal, which interferes with other things (there are previous tickets 
on this, a search for SIGALRM should turn them up).

Cheers,
	Simon