663dde1ad7
If a SHM or PHC refclock has a very large offset compensated by the offset option, or ignored with the pps or local option, there is a persistent loss of precision in the calculation of the sample offset using the double format. Rework the code to delay the calculation of the accumulated offset to include the specificed compensation and remaining correction of the system clock, where the calculation can be split to improve the precision. In the pps mode ignore integer seconds competely. The precision of the SOCK refclock is now limited to 1 nanosecond due to the extra double->timespec->double conversion.
134 lines
3.6 KiB
C
134 lines
3.6 KiB
C
/*
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chronyd/chronyc - Programs for keeping computer clocks accurate.
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**********************************************************************
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* Copyright (C) Miroslav Lichvar 2009
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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**********************************************************************
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=======================================================================
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SHM refclock driver.
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*/
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#include "config.h"
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#include "sysincl.h"
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#include "refclock.h"
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#include "logging.h"
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#include "util.h"
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#define SHMKEY 0x4e545030
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struct shmTime {
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int mode; /* 0 - if valid set
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* use values,
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* clear valid
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* 1 - if valid set
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* if count before and after read of values is equal,
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* use values
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* clear valid
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*/
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volatile int count;
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time_t clockTimeStampSec;
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int clockTimeStampUSec;
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time_t receiveTimeStampSec;
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int receiveTimeStampUSec;
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int leap;
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int precision;
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int nsamples;
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volatile int valid;
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int clockTimeStampNSec;
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int receiveTimeStampNSec;
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int dummy[8];
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};
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static int shm_initialise(RCL_Instance instance) {
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const char *options[] = {"perm", NULL};
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int id, param, perm;
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char *s;
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struct shmTime *shm;
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RCL_CheckDriverOptions(instance, options);
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param = atoi(RCL_GetDriverParameter(instance));
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s = RCL_GetDriverOption(instance, "perm");
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perm = s ? strtol(s, NULL, 8) & 0777 : 0600;
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id = shmget(SHMKEY + param, sizeof (struct shmTime), IPC_CREAT | perm);
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if (id == -1) {
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LOG_FATAL("shmget() failed : %s", strerror(errno));
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return 0;
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}
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shm = (struct shmTime *)shmat(id, 0, 0);
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if ((long)shm == -1) {
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LOG_FATAL("shmat() failed : %s", strerror(errno));
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return 0;
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}
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RCL_SetDriverData(instance, shm);
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return 1;
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}
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static void shm_finalise(RCL_Instance instance)
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{
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shmdt(RCL_GetDriverData(instance));
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}
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static int shm_poll(RCL_Instance instance)
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{
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struct timespec receive_ts, clock_ts;
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struct shmTime t, *shm;
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shm = (struct shmTime *)RCL_GetDriverData(instance);
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t = *shm;
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if ((t.mode == 1 && t.count != shm->count) ||
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!(t.mode == 0 || t.mode == 1) || !t.valid) {
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DEBUG_LOG("SHM sample ignored mode=%d count=%d valid=%d",
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t.mode, t.count, t.valid);
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return 0;
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}
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shm->valid = 0;
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receive_ts.tv_sec = t.receiveTimeStampSec;
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clock_ts.tv_sec = t.clockTimeStampSec;
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if (t.clockTimeStampNSec / 1000 == t.clockTimeStampUSec &&
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t.receiveTimeStampNSec / 1000 == t.receiveTimeStampUSec) {
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receive_ts.tv_nsec = t.receiveTimeStampNSec;
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clock_ts.tv_nsec = t.clockTimeStampNSec;
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} else {
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receive_ts.tv_nsec = 1000 * t.receiveTimeStampUSec;
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clock_ts.tv_nsec = 1000 * t.clockTimeStampUSec;
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}
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UTI_NormaliseTimespec(&clock_ts);
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UTI_NormaliseTimespec(&receive_ts);
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return RCL_AddSample(instance, &receive_ts, &clock_ts, t.leap);
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}
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RefclockDriver RCL_SHM_driver = {
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shm_initialise,
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shm_finalise,
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shm_poll
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};
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