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    SubjectRe: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support
    On Thu, 21 Jun 2012 16:10:23 -0700
    "H. Peter Anvin" <hpa@zytor.com> wrote:

    > On 06/21/2012 03:51 PM, Andrew Morton wrote:
    > >
    > > What *is* significant is the effect of a signedness change upon
    > > arithmetic, conversions, warnings, etc. And whether such a change
    > > might actually introduce bugs.
    > >
    > >
    > > Back away and ask the broader questions: why did ktime_t choose
    > > unsigned? Is time a signed concept? What is the right thing to do
    > > here, from a long-term design perspective?
    >
    > Time is definitely a signed concept -- it has no beginning or end (well,
    > the Big Bang, but the __110 Myr or so uncertainty of the exact timing of
    > the Big Bang makes it a horridly awkward choice for epoch.)
    >
    > Now, for some users of time you can inherently guarantee there will
    > never be any references to time before a particular event, e.g. system
    > boot, in which case an unsigned number might make sense, but as a whole
    > I think using a signed type as time_t in nearly all Unix implementation
    > was The Right Thing.
    >

    So why is ktime_t unsigned?


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