Hello, Xenomai version 2.4.10, Linux version 2.6.30.3, CPU PPC.
I am trying to work around an issue where the Linux and Xenomai realtime clocks drifts when Linux clock is updated by NTP. It was suggested in the mail exchange: http://www.mail-archive.com/[email protected]/msg07646.html to use clock_gettime()/clock_settime() to keep both clocks in sync. However, calling linux clock_gettime() from a Xenomai thread is causing system to freeze after a few minutes as shown in the following test program where the interval to re-sync clocks is small, 50 msec, to force error faster: #include <pthread.h> #include <time.h> #include <rtdk.h> #include <sys/mman.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> int __real_clock_gettime(clockid_t clock_id, struct timespec *tp); // Interval to sync clocks, 50 msec. #define CLOCK_SYNC_NSEC_INTERVAL 50000000 // Maximum clock drift tolerated, 2 msec. #define MAX_NSEC_DRIFT 2000000 void make_rt_thread() { int retval = 0; struct sched_param sparam; sparam.sched_priority = 1; if ((retval = pthread_setschedparam(pthread_self(), SCHED_FIFO, &sparam)) != 0) { rt_printf("pthread_setschedparam: %s\n", strerror(retval)); exit(retval); } } // Get Xenomai and Linux realtime clocks. // // return 0 on success and -1 otherwise. int get_realtime_clocks(struct timespec *pxeno, struct timespec *pposix) { if (clock_gettime(CLOCK_REALTIME, pxeno) != 0) { rt_printf("%s: error clock_gettime\n", __FUNCTION__); return -1; } if (__real_clock_gettime(CLOCK_REALTIME, pposix) != 0) { rt_printf("%s: error __real_clock_gettime\n", __FUNCTION__); return -1; } return 0; } // Synchronize Xenomai clock to Linux's. int sync_xeno_clock(struct timespec *pposix) { int retval; retval = clock_settime(CLOCK_REALTIME, pposix); if (retval != 0) { return -1; } return 0; } int main (int argc, char** argv) { struct timespec xeno_real, posix_real; struct timespec sync_interval; int retval; mlockall(MCL_CURRENT | MCL_FUTURE); make_rt_thread(); rt_print_auto_init(1); rt_print_init(16384, "SYNC_RT"); // sync clocks. retval = get_realtime_clocks(&xeno_real, &posix_real); if (retval != 0) { rt_printf("%s: cannot read clocks\n", __FUNCTION__); exit(1); } retval = sync_xeno_clock(&posix_real); if (retval != 0) { rt_printf("%s: cannot sync clock\n", __FUNCTION__); exit(1); } sync_interval.tv_sec = 0; sync_interval.tv_nsec = CLOCK_SYNC_NSEC_INTERVAL; // loop to keep clocks in sync. while (1) { nanosleep(&sync_interval, NULL); retval = get_realtime_clocks(&xeno_real, &posix_real); if (retval != 0) { continue; } if (xeno_real.tv_sec != posix_real.tv_sec) { // clocks drift, resync. retval = sync_xeno_clock(&posix_real); if (retval != 0) { rt_printf("%s: cannot resync clock\n", __FUNCTION__); continue; } } else if (labs(xeno_real.tv_nsec - posix_real.tv_nsec) > MAX_NSEC_DRIFT) { // clocks drift, resync. retval = sync_xeno_clock(&posix_real); if (retval != 0) { rt_printf("%s: cannot resync clock\n", __FUNCTION__); continue; } } } exit(1); } Thanks, Luis
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