Author: hselasky
Date: Wed Aug 1 11:08:52 2018
New Revision: 337036
URL: https://svnweb.freebsd.org/changeset/base/337036
Log:
MFC r321686 and r330361:
Add inline functions to convert between sbintime_t and decimal time units.
Use them in some existing code that is vulnerable to roundoff errors.
Modified:
stable/10/sys/arm/arm/mpcore_timer.c
stable/10/sys/sys/time.h
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/arm/arm/mpcore_timer.c
==============================================================================
--- stable/10/sys/arm/arm/mpcore_timer.c Wed Aug 1 10:35:49 2018
(r337035)
+++ stable/10/sys/arm/arm/mpcore_timer.c Wed Aug 1 11:08:52 2018
(r337036)
@@ -349,7 +349,7 @@ attach_et(struct arm_tmr_softc *sc)
sc->et.et_flags = ET_FLAGS_PERIODIC | ET_FLAGS_ONESHOT |
ET_FLAGS_PERCPU;
sc->et.et_quality = 1000;
sc->et.et_frequency = sc->clkfreq;
- sc->et.et_min_period = 20 * SBT_1NS;
+ sc->et.et_min_period = nstosbt(20);
sc->et.et_max_period = 2 * SBT_1S;
sc->et.et_start = arm_tmr_start;
sc->et.et_stop = arm_tmr_stop;
Modified: stable/10/sys/sys/time.h
==============================================================================
--- stable/10/sys/sys/time.h Wed Aug 1 10:35:49 2018 (r337035)
+++ stable/10/sys/sys/time.h Wed Aug 1 11:08:52 2018 (r337036)
@@ -128,7 +128,7 @@ bintime_shift(struct bintime *_bt, int _exp)
#define SBT_1M (SBT_1S * 60)
#define SBT_1MS (SBT_1S / 1000)
#define SBT_1US (SBT_1S / 1000000)
-#define SBT_1NS (SBT_1S / 1000000000)
+#define SBT_1NS (SBT_1S / 1000000000) /* beware rounding, see nstosbt()
*/
#define SBT_MAX 0x7fffffffffffffffLL
static __inline int
@@ -155,6 +155,53 @@ sbttobt(sbintime_t _sbt)
return (_bt);
}
+/*
+ * Decimal<->sbt conversions. Multiplying or dividing by SBT_1NS results in
+ * large roundoff errors which sbttons() and nstosbt() avoid. Millisecond and
+ * microsecond functions are also provided for completeness.
+ */
+static __inline int64_t
+sbttons(sbintime_t _sbt)
+{
+
+ return ((1000000000 * _sbt) >> 32);
+}
+
+static __inline sbintime_t
+nstosbt(int64_t _ns)
+{
+
+ return ((_ns * (((uint64_t)1 << 63) / 500000000)) >> 32);
+}
+
+static __inline int64_t
+sbttous(sbintime_t _sbt)
+{
+
+ return ((1000000 * _sbt) >> 32);
+}
+
+static __inline sbintime_t
+ustosbt(int64_t _us)
+{
+
+ return ((_us * (((uint64_t)1 << 63) / 500000)) >> 32);
+}
+
+static __inline int64_t
+sbttoms(sbintime_t _sbt)
+{
+
+ return ((1000 * _sbt) >> 32);
+}
+
+static __inline sbintime_t
+mstosbt(int64_t _ms)
+{
+
+ return ((_ms * (((uint64_t)1 << 63) / 500)) >> 32);
+}
+
/*-
* Background information:
*
@@ -210,7 +257,7 @@ sbttots(sbintime_t _sbt)
struct timespec _ts;
_ts.tv_sec = _sbt >> 32;
- _ts.tv_nsec = ((uint64_t)1000000000 * (uint32_t)_sbt) >> 32;
+ _ts.tv_nsec = sbttons((uint32_t)_sbt);
return (_ts);
}
@@ -218,8 +265,7 @@ static __inline sbintime_t
tstosbt(struct timespec _ts)
{
- return (((sbintime_t)_ts.tv_sec << 32) +
- (_ts.tv_nsec * (((uint64_t)1 << 63) / 500000000) >> 32));
+ return (((sbintime_t)_ts.tv_sec << 32) + nstosbt(_ts.tv_nsec));
}
static __inline struct timeval
@@ -228,7 +274,7 @@ sbttotv(sbintime_t _sbt)
struct timeval _tv;
_tv.tv_sec = _sbt >> 32;
- _tv.tv_usec = ((uint64_t)1000000 * (uint32_t)_sbt) >> 32;
+ _tv.tv_usec = sbttous((uint32_t)_sbt);
return (_tv);
}
@@ -236,8 +282,7 @@ static __inline sbintime_t
tvtosbt(struct timeval _tv)
{
- return (((sbintime_t)_tv.tv_sec << 32) +
- (_tv.tv_usec * (((uint64_t)1 << 63) / 500000) >> 32));
+ return (((sbintime_t)_tv.tv_sec << 32) + ustosbt(_tv.tv_usec));
}
#endif /* __BSD_VISIBLE */
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