On Thu, 21 Jun 2012 16:15:58 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 21 Jun 2012 16:10:23 -0700 > "H. Peter Anvin" <hpa@xxxxxxxxx> 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? err, actually, it isn't. But lots of the APIs to manipulate ktime_t use u64. Reason? I do agree that time quantities should be signed. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html