ardupilot/libraries/AP_HAL_Linux/Scheduler.cpp

#include <AP_HAL.h>

#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX

#include "Scheduler.h"
#include "Storage.h"
#include "RCInput.h"
#include "UARTDriver.h"
#include "Util.h"
#include "SPIUARTDriver.h"
#include <sys/time.h>
#include <poll.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>

using namespace Linux;

extern const AP_HAL::HAL& hal;

#define APM_LINUX_TIMER_PRIORITY        15
#define APM_LINUX_UART_PRIORITY         14
#define APM_LINUX_RCIN_PRIORITY         13
#define APM_LINUX_MAIN_PRIORITY         12
#define APM_LINUX_TONEALARM_PRIORITY    11
#define APM_LINUX_IO_PRIORITY           10

LinuxScheduler::LinuxScheduler()
{}

void LinuxScheduler::_create_realtime_thread(pthread_t *ctx, int rtprio,
                                             const char *name,
                                             pthread_startroutine_t start_routine)
{
    struct sched_param param = { .sched_priority = rtprio };
    pthread_attr_t attr;
    int r;

    pthread_attr_init(&attr);
    /*
      we need to run as root to get realtime scheduling. Allow it to
      run as non-root for debugging purposes, plus to allow the Replay
      tool to run
     */
    if (geteuid() == 0) {
        pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
        pthread_attr_setschedpolicy(&attr, SCHED_FIFO);
        pthread_attr_setschedparam(&attr, &param);
    }
    r = pthread_create(ctx, &attr, start_routine, this);
    if (r != 0) {
        hal.console->printf("Error creating thread '%s': %s\n",
                            name, strerror(r));
        panic(PSTR("Failed to create thread"));
    }
    pthread_attr_destroy(&attr);

    if (name) {
        pthread_setname_np(*ctx, name);
    }
}

void LinuxScheduler::init(void* machtnichts)
{
    mlockall(MCL_CURRENT|MCL_FUTURE);

    clock_gettime(CLOCK_MONOTONIC, &_sketch_start_time);

    struct sched_param param = { .sched_priority = APM_LINUX_MAIN_PRIORITY };
    sched_setscheduler(0, SCHED_FIFO, &param);

    struct {
        pthread_t *ctx;
        int rtprio;
        const char *name;
        pthread_startroutine_t start_routine;
    } *iter, table[] = {
        { .ctx = &_timer_thread_ctx,
          .rtprio = APM_LINUX_TIMER_PRIORITY,
          .name = "sched-timer",
          .start_routine = &Linux::LinuxScheduler::_timer_thread,
        },
        { .ctx = &_uart_thread_ctx,
          .rtprio = APM_LINUX_UART_PRIORITY,
          .name = "sched-uart",
          .start_routine = &Linux::LinuxScheduler::_uart_thread,
        },
        { .ctx = &_rcin_thread_ctx,
          .rtprio = APM_LINUX_RCIN_PRIORITY,
          .name = "sched-rcin",
          .start_routine = &Linux::LinuxScheduler::_rcin_thread,
        },
        { .ctx = &_tonealarm_thread_ctx,
          .rtprio = APM_LINUX_TONEALARM_PRIORITY,
          .name = "sched-tonealarm",
          .start_routine = &Linux::LinuxScheduler::_tonealarm_thread,
        },
        { .ctx = &_io_thread_ctx,
          .rtprio = APM_LINUX_IO_PRIORITY,
          .name = "sched-io",
          .start_routine = &Linux::LinuxScheduler::_io_thread,
        },
        { }
    };

    if (geteuid() != 0) {
        printf("WARNING: running as non-root. Will not use realtime scheduling\n");
    }

    for (iter = table; iter->ctx; iter++)
        _create_realtime_thread(iter->ctx, iter->rtprio, iter->name,
                                iter->start_routine);
}

void LinuxScheduler::_microsleep(uint32_t usec)
{
    struct timespec ts;
    ts.tv_sec = 0;
    ts.tv_nsec = usec*1000UL;
    while (nanosleep(&ts, &ts) == -1 && errno == EINTR) ;
}

void LinuxScheduler::delay(uint16_t ms)
{
    if (stopped_clock_usec) {
        return;
    }
    uint64_t start = millis64();
    
    while ((millis64() - start) < ms) {
        // this yields the CPU to other apps
        _microsleep(1000);
        if (_min_delay_cb_ms <= ms) {
            if (_delay_cb) {
                _delay_cb();
            }
        }
    }
}

uint64_t LinuxScheduler::millis64() 
{
    if (stopped_clock_usec) {
        return stopped_clock_usec/1000;
    }
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return 1.0e3*((ts.tv_sec + (ts.tv_nsec*1.0e-9)) - 
                  (_sketch_start_time.tv_sec +
                   (_sketch_start_time.tv_nsec*1.0e-9)));
}

uint64_t LinuxScheduler::micros64() 
{
    if (stopped_clock_usec) {
        return stopped_clock_usec;
    }
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return 1.0e6*((ts.tv_sec + (ts.tv_nsec*1.0e-9)) - 
                  (_sketch_start_time.tv_sec +
                   (_sketch_start_time.tv_nsec*1.0e-9)));
}

uint32_t LinuxScheduler::millis() 
{
    return millis64() & 0xFFFFFFFF;
}

uint32_t LinuxScheduler::micros() 
{
    return micros64() & 0xFFFFFFFF;
}

void LinuxScheduler::delay_microseconds(uint16_t us)
{
    if (stopped_clock_usec) {
        return;
    }
    _microsleep(us);
}

void LinuxScheduler::register_delay_callback(AP_HAL::Proc proc,
                                             uint16_t min_time_ms)
{
    _delay_cb = proc;
    _min_delay_cb_ms = min_time_ms;
}

void LinuxScheduler::register_timer_process(AP_HAL::MemberProc proc) 
{
    for (uint8_t i = 0; i < _num_timer_procs; i++) {
        if (_timer_proc[i] == proc) {
            return;
        }
    }

    if (_num_timer_procs < LINUX_SCHEDULER_MAX_TIMER_PROCS) {
        _timer_proc[_num_timer_procs] = proc;
        _num_timer_procs++;
    } else {
        hal.console->printf("Out of timer processes\n");
    }
}

void LinuxScheduler::register_io_process(AP_HAL::MemberProc proc) 
{
    for (uint8_t i = 0; i < _num_io_procs; i++) {
        if (_io_proc[i] == proc) {
            return;
        }
    }

    if (_num_io_procs < LINUX_SCHEDULER_MAX_IO_PROCS) {
        _io_proc[_num_io_procs] = proc;
        _num_io_procs++;
    } else {
        hal.console->printf("Out of IO processes\n");
    }
}

void LinuxScheduler::register_timer_failsafe(AP_HAL::Proc failsafe, uint32_t period_us)
{
    _failsafe = failsafe;
}

void LinuxScheduler::suspend_timer_procs()
{
    if (!_timer_semaphore.take(0)) {
        printf("Failed to take timer semaphore\n");
    }
}

void LinuxScheduler::resume_timer_procs()
{
    _timer_semaphore.give();
}

void LinuxScheduler::_run_timers(bool called_from_timer_thread)
{
    if (_in_timer_proc) {
        return;
    }
    _in_timer_proc = true;

    if (!_timer_semaphore.take(0)) {
        printf("Failed to take timer semaphore in _run_timers\n");
    }
    // now call the timer based drivers
    for (int i = 0; i < _num_timer_procs; i++) {
        if (_timer_proc[i]) {
            _timer_proc[i]();
        }
    }
    _timer_semaphore.give();

    // and the failsafe, if one is setup
    if (_failsafe != NULL) {
        _failsafe();
    }

    _in_timer_proc = false;
}

void *LinuxScheduler::_timer_thread(void* arg)
{
    LinuxScheduler* sched = (LinuxScheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    /*
      this aims to run at an average of 1kHz, so that it can be used
      to drive 1kHz processes without drift
     */
    uint64_t next_run_usec = sched->micros64() + 1000;
    while (true) {
        uint64_t dt = next_run_usec - sched->micros64();
        if (dt > 2000) {
            // we've lost sync - restart
            next_run_usec = sched->micros64();
        } else {
            sched->_microsleep(dt);
        }
        next_run_usec += 1000;
        // run registered timers
        sched->_run_timers(true);
    }
    return NULL;
}

void LinuxScheduler::_run_io(void)
{
    if (!_io_semaphore.take(0)) {
        return;
    }

    // now call the IO based drivers
    for (int i = 0; i < _num_io_procs; i++) {
        if (_io_proc[i]) {
            _io_proc[i]();
        }
    }

    _io_semaphore.give();
}

void *LinuxScheduler::_rcin_thread(void *arg)
{
    LinuxScheduler* sched = (LinuxScheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(10000);

        ((LinuxRCInput *)hal.rcin)->_timer_tick();
    }
    return NULL;
}

void *LinuxScheduler::_uart_thread(void* arg)
{
    LinuxScheduler* sched = (LinuxScheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(10000);

        // process any pending serial bytes
        ((LinuxUARTDriver *)hal.uartA)->_timer_tick();
        ((LinuxUARTDriver *)hal.uartB)->_timer_tick();
        ((LinuxUARTDriver *)hal.uartC)->_timer_tick();
        ((LinuxUARTDriver *)hal.uartE)->_timer_tick();
    }
    return NULL;
}

void *LinuxScheduler::_tonealarm_thread(void* arg)
{
    LinuxScheduler* sched = (LinuxScheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(10000);

        // process tone command
        ((LinuxUtil *)hal.util)->_toneAlarm_timer_tick();
    }
    return NULL;
}

void *LinuxScheduler::_io_thread(void* arg)
{
    LinuxScheduler* sched = (LinuxScheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(20000);

        // process any pending storage writes
        ((LinuxStorage *)hal.storage)->_timer_tick();

        // run registered IO processes
        sched->_run_io();
    }
    return NULL;
}

void LinuxScheduler::panic(const prog_char_t *errormsg) 
{
    write(1, errormsg, strlen(errormsg));
    write(1, "\n", 1);
    hal.scheduler->delay_microseconds(10000);
    exit(1);
}

bool LinuxScheduler::in_timerprocess() 
{
    return _in_timer_proc;
}

void LinuxScheduler::begin_atomic()
{}

void LinuxScheduler::end_atomic()
{}

bool LinuxScheduler::system_initializing() {
    return !_initialized;
}

void LinuxScheduler::system_initialized()
{
    if (_initialized) {
        panic("PANIC: scheduler::system_initialized called more than once");
    }
    _initialized = true;
}

void LinuxScheduler::reboot(bool hold_in_bootloader) 
{
    exit(1);
}

void LinuxScheduler::stop_clock(uint64_t time_usec)
{
    if (time_usec >= stopped_clock_usec) {
        stopped_clock_usec = time_usec;
        _run_io();
    }
}

#endif // CONFIG_HAL_BOARD