Date: Sun, 27 Aug 2006 22:14:09 -0700
From: Chris Wedgwood <cw@f00f.org>
To: Paul Mackerras <paulus@samba.org>
Cc: Dong Feng <middle.fengdong@gmail.com>, ak@suse.de,
       Christoph Lameter <clameter@sgi.com>, linux-kernel@vger.kernel.org
Subject: Re: Why Semaphore Hardware-Dependent?
Message-ID: <20060828051409.GA17891@tuatara.stupidest.org>
References: <a2ebde260608271222x2b51693fnaa600965fcfaa6d2@mail.gmail.com> <17650.13915.413019.784343@cargo.ozlabs.ibm.com>
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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).
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