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AP_HAL_Linux: use pthread's barrier instead of polling

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Use pthread's barrier so we don't keep waking up threads with possibly
higher priority during initialization phase.

This also synchronizes all of them to a single point. With the previous
approach it was possible (but unlikely) that a thread hadn't reach the
synchronization point when main thread signalize "system initialized".
This commit is contained in:
Lucas De Marchi 2016-02-03 01:42:47 -02:00
parent 2b0e214168
commit 9cf9fc152b
2 changed files with 18 additions and 4 deletions
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18
libraries/AP_HAL_Linux/Scheduler.cpp
View File

@ -3,7 +3,6 @@
#include <algorithm>
#include <errno.h>
#include <poll.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
@ -66,6 +65,8 @@ void Scheduler::init()
struct sched_param param = { .sched_priority = APM_LINUX_MAIN_PRIORITY };
sched_setscheduler(0, SCHED_FIFO, &param);
/* set barrier to 6 threads: worker threads below + main thread */
pthread_barrier_init(&_initialized_barrier, nullptr, 6);
_timer_thread.start("sched-timer", SCHED_FIFO, APM_LINUX_TIMER_PRIORITY);
_uart_thread.start("sched-uart", SCHED_FIFO, APM_LINUX_UART_PRIORITY);
_rcin_thread.start("sched-rcin", SCHED_FIFO, APM_LINUX_RCIN_PRIORITY);
@ -406,12 +407,23 @@ bool Scheduler::system_initializing() {
return !_initialized;
}
void Scheduler::_wait_all_threads()
{
int r = pthread_barrier_wait(&_initialized_barrier);
if (r == PTHREAD_BARRIER_SERIAL_THREAD) {
pthread_barrier_destroy(&_initialized_barrier);
}
}
void Scheduler::system_initialized()
{
if (_initialized) {
AP_HAL::panic("PANIC: scheduler::system_initialized called more than once");
}
_initialized = true;
_wait_all_threads();
}
void Scheduler::reboot(bool hold_in_bootloader)
@ -429,9 +441,7 @@ void Scheduler::stop_clock(uint64_t time_usec)
bool Scheduler::SchedulerThread::_run()
{
while (_sched.system_initializing()) {
poll(NULL, 0, 1);
}
_sched._wait_all_threads();
return Thread::_run();
}

4
libraries/AP_HAL_Linux/Scheduler.h
View File

@ -1,5 +1,7 @@
#pragma once
#include <pthread.h>
#include "AP_HAL_Linux.h"
#include "Semaphores.h"
#include "Thread.h"
@ -60,6 +62,7 @@ private:
Scheduler &_sched;
};
void _wait_all_threads();
void _timer_handler(int signum);
AP_HAL::Proc _delay_cb;
@ -68,6 +71,7 @@ private:
AP_HAL::Proc _failsafe;
bool _initialized;
pthread_barrier_t _initialized_barrier;
volatile bool _timer_pending;
AP_HAL::MemberProc _timer_proc[LINUX_SCHEDULER_MAX_TIMER_PROCS];