Re: Why Semaphore Hardware-Dependent?

Chris Wedgwood
2006-08-28T05:14:15Z

On Mon, Aug 28, 2006 at 10:18:35AM +1000, Paul Mackerras wrote:

> I believe the reason for not doing something like this on x86 was
> the fact that we still support i386 processors, which don't have the
> cmpxchg instruction. That's fair enough, but I would be opposed to
> making semaphores bigger and slower on PowerPC because of that.
> Hence the two different styles of implementation.

The i386 is older than some of the kernel hackers, and given that a
modern kernel is pretty painful with less than say 16MB or RAM in
practice, I don't see that it would be all that terrible to drop
support for ancient CPUs at some point (yes, I know some newer
embedded (and similar) CPUs might be affected here too, but surely not
that many that people really use --- and they could just use 2.4.x).