clock.c

/**
 * @file
 * @author Erling Jellum
 * @copyright (c) 2020-2024, The University of California at Berkeley.
 * License: <a href="https://github.com/lf-lang/reactor-c/blob/main/LICENSE.md">BSD 2-clause</a>
 * @brief Implementations of functions in clock.h.
*/
#include "clock.h"
#include "platform.h"

#if defined(_LF_CLOCK_SYNC_ON)
#include "clock-sync.h"
#endif

static instant_t last_read_physical_time = NEVER;

int lf_clock_gettime(instant_t *now) {
    instant_t last_read_local;
    int res = _lf_clock_gettime(now);
    if (res != 0) {
        return -1;
    }
    #if defined (_LF_CLOCK_SYNC_ON)
    clock_sync_apply_offset(now);
    #endif
    do {
        // Atomically fetch the last read value. This is done with
        // atomics to guarantee that it works on 32bit platforms as well.
        last_read_local = lf_atomic_fetch_add64(&last_read_physical_time, 0);
    
        // Ensure monotonicity. 
        if (*now < last_read_local) {
            *now = last_read_local+1;
        }

        // Update the last read value, atomically and also make sure that another
        // thread has not been here in between and changed it. If so. We must redo
        // the monotonicity calculation.
    } while(!lf_atomic_bool_compare_and_swap64(&last_read_physical_time, last_read_local, *now));

    return 0;
}

int lf_clock_interruptable_sleep_until_locked(environment_t *env, instant_t wakeup_time) {
    #if defined (_LF_CLOCK_SYNC_ON)
    // Remove any clock sync offset and call the Platform API.
    clock_sync_remove_offset(&wakeup_time);
    #endif
    return _lf_interruptable_sleep_until_locked(env, wakeup_time);
}

#if !defined(LF_SINGLE_THREADED)
int lf_clock_cond_timedwait(lf_cond_t *cond, instant_t wakeup_time) {
    #if defined (_LF_CLOCK_SYNC_ON)
    // Remove any clock sync offset and call the Platform API.
    clock_sync_remove_offset(&wakeup_time);
    #endif
    // return _lf_cond_timedwait(cond, wakeup_time);
    while (lf_time_physical() < wakeup_time);
    return true;
}
#endif