On Thu, 21 Jun 2012 15:47:49 -0700 "H. Peter Anvin" <hpa@xxxxxxxxx> wrote: > On 06/21/2012 03:43 PM, Andrew Morton wrote: > > > > Regardless of that, we have some head-scratching to do: > > > > > > #define UNCORE_PMU_HRTIMER_INTERVAL (60 * NSEC_PER_SEC) > > > > and > > > > #define NSEC_PER_SEC 1000000000L > > > > and 60 billion doesn't fit in 32 bits. So do we fix the > > perf_event_intel_uncore.c callsites? Or do we fix the > > UNCORE_PMU_HRTIMER_INTERVAL definition? Or do we fix the NSEC_PER_SEC > > definition? > > > > I'm thinking perhaps the latter. What *is* the type of a nanosecond in > > Linux? include/linux/ktime.h is pretty insistent that it is u64. If > > so, NSEC_PER_SEC should logically have type ULL. But changing both its > > size and signedness is a pretty big change. > > We could change the size only. The range from 9223372036.854775808 to > 18446744073.709551615 seconds (292-584 years) isn't really that significant. > 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? -- 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
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