[rtems commit] timecounter: Synchronize with FreeBSD
Sebastian Huber
sebh at rtems.org
Tue Jun 9 13:19:51 UTC 2015
Module: rtems
Branch: master
Commit: e1d61fe2aaefa13c45154f7ffedf43fe4c0c4efd
Changeset: http://git.rtems.org/rtems/commit/?id=e1d61fe2aaefa13c45154f7ffedf43fe4c0c4efd
Author: kib <kib at FreeBSD.org>
Date: Tue Jun 9 11:49:56 2015 +0000
timecounter: Synchronize with FreeBSD
When updating/accessing the timehands, barriers are needed to ensure
that:
- th_generation update is visible after the parameters update is
visible;
- the read of parameters is not reordered before initial read of
th_generation.
On UP kernels, compiler barriers are enough. For SMP machines, CPU
barriers must be used too, as was confirmed by submitter by testing on
the Freescale T4240 platform with 24 PowerPC processors.
Submitted by: Sebastian Huber <sebastian.huber at embedded-brains.de>
MFC after: 1 week
---
cpukit/score/src/kern_tc.c | 124 ++++++++++++++++++++++++++++++---------------
1 file changed, 82 insertions(+), 42 deletions(-)
diff --git a/cpukit/score/src/kern_tc.c b/cpukit/score/src/kern_tc.c
index 654703d..f6a1136 100644
--- a/cpukit/score/src/kern_tc.c
+++ b/cpukit/score/src/kern_tc.c
@@ -36,7 +36,7 @@
#include <rtems/score/watchdogimpl.h>
#endif /* __rtems__ */
#include <sys/cdefs.h>
-__FBSDID("$FreeBSD r282424 2015-05-04T17:59:39Z$");
+__FBSDID("$FreeBSD r284178 2015-06-09T11:49:56Z$");
#include "opt_compat.h"
#include "opt_ntp.h"
@@ -59,6 +59,7 @@ __FBSDID("$FreeBSD r282424 2015-05-04T17:59:39Z$");
#include <sys/timex.h>
#ifndef __rtems__
#include <sys/vdso.h>
+#include <machine/atomic.h>
#endif /* __rtems__ */
#ifdef __rtems__
#include <limits.h>
@@ -116,7 +117,11 @@ struct timehands {
struct timeval th_microtime;
struct timespec th_nanotime;
/* Fields not to be copied in tc_windup start with th_generation. */
- volatile uint32_t th_generation;
+#ifndef __rtems__
+ u_int th_generation;
+#else /* __rtems__ */
+ Atomic_Ulong th_generation;
+#endif /* __rtems__ */
struct timehands *th_next;
};
@@ -248,6 +253,41 @@ tc_delta(struct timehands *th)
tc->tc_counter_mask);
}
+static u_int
+tc_getgen(struct timehands *th)
+{
+
+#ifndef __rtems__
+#ifdef SMP
+ return (atomic_load_acq_int(&th->th_generation));
+#else
+ u_int gen;
+
+ gen = th->th_generation;
+ __compiler_membar();
+ return (gen);
+#endif
+#else /* __rtems__ */
+ return (_Atomic_Load_ulong(&th->th_generation, ATOMIC_ORDER_ACQUIRE));
+#endif /* __rtems__ */
+}
+
+static void
+tc_setgen(struct timehands *th, u_int newgen)
+{
+
+#ifndef __rtems__
+#ifdef SMP
+ atomic_store_rel_int(&th->th_generation, newgen);
+#else
+ __compiler_membar();
+ th->th_generation = newgen;
+#endif
+#else /* __rtems__ */
+ _Atomic_Store_ulong(&th->th_generation, newgen, ATOMIC_ORDER_RELEASE);
+#endif /* __rtems__ */
+}
+
/*
* Functions for reading the time. We have to loop until we are sure that
* the timehands that we operated on was not updated under our feet. See
@@ -263,10 +303,10 @@ fbclock_binuptime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
bintime_addx(bt, th->th_scale * tc_delta(th));
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -321,9 +361,9 @@ fbclock_getbinuptime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -334,9 +374,9 @@ fbclock_getnanouptime(struct timespec *tsp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
bintime2timespec(&th->th_offset, tsp);
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -347,9 +387,9 @@ fbclock_getmicrouptime(struct timeval *tvp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
bintime2timeval(&th->th_offset, tvp);
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -360,9 +400,9 @@ fbclock_getbintime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
bintime_add(bt, &boottimebin);
}
@@ -374,9 +414,9 @@ fbclock_getnanotime(struct timespec *tsp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*tsp = th->th_nanotime;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -387,9 +427,9 @@ fbclock_getmicrotime(struct timeval *tvp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*tvp = th->th_microtime;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
#else /* !FFCLOCK */
void
@@ -400,10 +440,10 @@ binuptime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
bintime_addx(bt, th->th_scale * tc_delta(th));
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -458,9 +498,9 @@ getbinuptime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -471,9 +511,9 @@ getnanouptime(struct timespec *tsp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
bintime2timespec(&th->th_offset, tsp);
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -484,9 +524,9 @@ getmicrouptime(struct timeval *tvp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
bintime2timeval(&th->th_offset, tvp);
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -497,9 +537,9 @@ getbintime(struct bintime *bt)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*bt = th->th_offset;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
bintime_add(bt, &boottimebin);
}
@@ -511,9 +551,9 @@ getnanotime(struct timespec *tsp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*tsp = th->th_nanotime;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
void
@@ -524,9 +564,9 @@ getmicrotime(struct timeval *tvp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*tvp = th->th_microtime;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
#endif /* FFCLOCK */
@@ -939,11 +979,11 @@ ffclock_read_counter(ffcounter *ffcount)
*/
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
ffth = fftimehands;
delta = tc_delta(th);
*ffcount = ffth->tick_ffcount;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
*ffcount += delta;
}
@@ -1048,9 +1088,9 @@ dtrace_getnanotime(struct timespec *tsp)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
*tsp = th->th_nanotime;
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
}
#endif /* __rtems__ */
@@ -1092,7 +1132,7 @@ sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
do {
th = timehands;
- gen = th->th_generation;
+ gen = tc_getgen(th);
fbi->th_scale = th->th_scale;
fbi->tick_time = th->th_offset;
#ifdef FFCLOCK
@@ -1106,7 +1146,7 @@ sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
#endif
if (!fast)
delta = tc_delta(th);
- } while (gen == 0 || gen != th->th_generation);
+ } while (gen == 0 || gen != tc_getgen(th));
clock_snap->delta = delta;
#ifdef FFCLOCK
@@ -1354,7 +1394,7 @@ tc_windup(void)
tho = timehands;
th = tho->th_next;
ogen = th->th_generation;
- th->th_generation = 0;
+ tc_setgen(th, 0);
bcopy(tho, th, offsetof(struct timehands, th_generation));
/*
@@ -1475,7 +1515,7 @@ tc_windup(void)
*/
if (++ogen == 0)
ogen = 1;
- th->th_generation = ogen;
+ tc_setgen(th, ogen);
/* Go live with the new struct timehands. */
#ifdef FFCLOCK
@@ -1757,13 +1797,13 @@ pps_capture(struct pps_state *pps)
KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
th = timehands;
- pps->capgen = th->th_generation;
+ pps->capgen = tc_getgen(th);
pps->capth = th;
#ifdef FFCLOCK
pps->capffth = fftimehands;
#endif
pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
- if (pps->capgen != th->th_generation)
+ if (pps->capgen != tc_getgen(th))
pps->capgen = 0;
}
@@ -1783,7 +1823,7 @@ pps_event(struct pps_state *pps, int event)
KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
/* If the timecounter was wound up underneath us, bail out. */
- if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
+ if (pps->capgen == 0 || pps->capgen != tc_getgen(pps->capth))
return;
/* Things would be easier with arrays. */
@@ -1833,7 +1873,7 @@ pps_event(struct pps_state *pps, int event)
bintime2timespec(&bt, &ts);
/* If the timecounter was wound up underneath us, bail out. */
- if (pps->capgen != pps->capth->th_generation)
+ if (pps->capgen != tc_getgen(pps->capth))
return;
*pcount = pps->capcount;
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