rt_os-xenomai.cpp

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/*
 The Real-Time eXperiment Interface (RTXI)
 Copyright (C) 2011 Georgia Institute of Technology, University of Utah, Weill Cornell Medical College

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program. If not, see <http://www.gnu.org/licenses/>.

*/

#include <debug.h>
#include <pthread.h>
#include <rt.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <native/task.h>
#include <native/timer.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <getopt.h>
#include <execinfo.h>
#include <unistd.h>

typedef struct
{
 long long period;
 long long next_t;
 long long wakeup_t;
 RT_TASK task;
} xenomai_task_t;

static bool init_rt = false;
static pthread_key_t is_rt_key;

static const char *sigdebug_reasons[] =
{
 [SIGDEBUG_UNDEFINED] = "latency: received SIGXCPU for unknown reason",
 [SIGDEBUG_MIGRATE_SIGNAL] = "received signal",
 [SIGDEBUG_MIGRATE_SYSCALL] = "invoked syscall",
 [SIGDEBUG_MIGRATE_FAULT] = "triggered fault",
 [SIGDEBUG_MIGRATE_PRIOINV] = "affected by priority inversion",
 [SIGDEBUG_NOMLOCK] = "Xenomai: process memory not locked "
 "(missing mlockall?)",
 [SIGDEBUG_WATCHDOG] = "Xenomai: watchdog triggered "
 "(period too short?)",
};

void sigdebug_handler(int sig, siginfo_t *si, void *context)
{
 const char fmt[] = "Mode switch (reason: %s), aborting. Backtrace:\n";
 unsigned int reason = si->si_value.sival_int;
 static char buffer[256];
 static void *bt[200];
 unsigned int n;

 if (reason > SIGDEBUG_WATCHDOG)
 reason = SIGDEBUG_UNDEFINED;

 switch(reason)
 {
 case SIGDEBUG_UNDEFINED:
 n = snprintf(buffer, sizeof(buffer),
 "%s\n", sigdebug_reasons[reason]);
 write(STDERR_FILENO, buffer, n);
 case SIGDEBUG_MIGRATE_SIGNAL:
 n = snprintf(buffer, sizeof(buffer),
 "%s\n", sigdebug_reasons[reason]);
 write(STDERR_FILENO, buffer, n);
 case SIGDEBUG_WATCHDOG:
 /* These errors are lethal, something went really wrong. */
 n = snprintf(buffer, sizeof(buffer),
 "%s\n", sigdebug_reasons[reason]);
 write(STDERR_FILENO, buffer, n);
 exit(EXIT_FAILURE);
 }

 /* Retrieve the current backtrace, and decode it to stdout. */
 n = snprintf(buffer, sizeof(buffer), fmt, sigdebug_reasons[reason]);
 n = write(STDERR_FILENO, buffer, n);
 n = backtrace(bt, sizeof(bt)/sizeof(bt[0]));
 backtrace_symbols_fd(bt, n, STDERR_FILENO);

 signal(sig, SIG_DFL);
 kill(getpid(), sig);
}

int RT::OS::initiate(void)
{
 rt_timer_set_mode(TM_ONESHOT);

 // Kernel limitations on memory lock are no longer present, however
 // still a useful (for performance) method for preventing paging
 // of active RTXI memory
 struct rlimit rlim = { RLIM_INFINITY, RLIM_INFINITY };
 setrlimit(RLIMIT_MEMLOCK,&rlim);

 if (mlockall(MCL_CURRENT | MCL_FUTURE))
 {
 ERROR_MSG("RTOS:Xenomai::initiate : failed to lock memory.\n");
 return -EPERM;
 }

 pthread_key_create(&is_rt_key,0);
 init_rt = true;

 return 0;
}

void RT::OS::shutdown(void)
{
 pthread_key_delete(is_rt_key);
}

int RT::OS::createTask(RT::OS::Task *task,void *(*entry)(void *),void *arg,int prio)
{
 int retval = 0;
 xenomai_task_t *t = new xenomai_task_t;
 int priority = 99;

 // Assign signal handler
 struct sigaction sa;
 sigemptyset(&sa.sa_mask);
 sa.sa_sigaction = sigdebug_handler;
 sa.sa_flags = SA_SIGINFO;
 sigaction(SIGDEBUG, &sa, NULL);

 // Tell Xenomai to report mode issues
 rt_task_set_mode(0, T_WARNSW, NULL);

 // Invert priority, default prio=0 but max priority for xenomai task is 99
 if ((prio >=0) && (prio <=99))
 priority -= prio;

 if ((retval = rt_task_create(&t->task,"RTXI RT Thread",0,priority,T_FPU)))
 {
 ERROR_MSG("RT::OS::createTask : failed to create task\n");
 return retval;
 }

 t->period = -1;

 *task = t;
 pthread_setspecific(is_rt_key,reinterpret_cast<const void *>(t));

 if ((retval = rt_task_start(&t->task,reinterpret_cast<void(*)(void *)>(entry),arg)))
 {
 ERROR_MSG("RT::OS::createTask : failed to start task\n");
 return retval;
 }

 return 0;
}

void RT::OS::deleteTask(RT::OS::Task task)
{
 xenomai_task_t *t = reinterpret_cast<xenomai_task_t *>(task);
 rt_task_delete(&t->task);
}

bool RT::OS::isRealtime(void)
{
 if (init_rt && pthread_getspecific(is_rt_key))
 return true;
 return false;
}

long long RT::OS::getTime(void)
{
 return rt_timer_tsc2ns(rt_timer_tsc());
}

int RT::OS::setPeriod(RT::OS::Task task,long long period)
{
 // Retrieve task struct
 xenomai_task_t *t = reinterpret_cast<xenomai_task_t *>(task);

 // Set wake up limits
 if(period/10 > 50000ll)
 t->wakeup_t = rt_timer_ns2ticks(50000ll);
 else
 t->wakeup_t = rt_timer_ns2ticks(period/10);

 // Setup timing bounds for oneshot operation
 t->period = rt_timer_ns2ticks(period);
 t->next_t = rt_timer_read() + t->period;

 return 0;
}

void RT::OS::sleepTimestep(RT::OS::Task task)
{
 xenomai_task_t *t = reinterpret_cast<xenomai_task_t *>(task);

 // Prevent significant early wake up from happening and drying the Linux system
 rt_task_sleep_until(t->next_t - t->wakeup_t);

 // Busy sleep until ready for the next cycle
 rt_timer_spin(rt_timer_ticks2ns(t->next_t - rt_timer_read()));

 // Update next interrupt time
 t->next_t += t->period;
}