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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    On Wed, Aug 15, 2007 at 10:48:28PM +0530, Satyam Sharma wrote:
    > On Wed, 15 Aug 2007, Paul E. McKenney wrote:
    > > On Wed, Aug 15, 2007 at 11:33:36PM +0800, Herbert Xu wrote:
    > > > On Wed, Aug 15, 2007 at 07:25:16AM -0700, Paul E. McKenney wrote:
    > > > >
    > > > > Do we really need another set of APIs? Can you give even one example
    > > > > where the pre-existing volatile semantics are causing enough of a problem
    > > > > to justify adding yet more atomic_*() APIs?
    > > >
    > > > Let's turn this around. Can you give a single example where
    > > > the volatile semantics is needed in a legitimate way?
    > >
    > > Sorry, but you are the one advocating for the change.
    >
    > Not for i386 and x86_64 -- those have atomic ops without any "volatile"
    > semantics (currently as per existing definitions).

    I claim unit volumes with arm, and the majority of the architectures, but
    I cannot deny the popularity of i386 and x86_64 with many developers. ;-)

    However, I am not aware of code in the kernel that would benefit
    from the compiler coalescing multiple atomic_set() and atomic_read()
    invocations, thus I don't see the downside to volatility in this case.
    Are there some performance-critical code fragments that I am missing?

    Thanx, Paul
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