Messages in this thread | | | Date | Sun, 27 Aug 2006 22:21:17 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: Why Semaphore Hardware-Dependent? |
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On Sun, 27 Aug 2006, Chris Wedgwood wrote:
> 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).
Also note that i386 has a cmpxchg emulation for those machines that do not support cmpxchg.
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