condition_variable.cpp
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/*
* Copyright (C) 2015 Hamburg University of Applied Sciences (HAW)
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpp11-compat
* @{
*
* @file
* @brief C++11 condition variable drop in replacement
*
* @author Raphael Hiesgen <raphael.hiesgen (at) haw-hamburg.de>
*
* @}
*/
#include <stdexcept>
#include <system_error>
#include "irq.h"
#include "sched.h"
#include "thread.h"
#include "timex.h"
#include "xtimer.h"
#include "priority_queue.h"
#include "riot/condition_variable.hpp"
using namespace std::chrono;
namespace riot {
condition_variable::~condition_variable() { m_queue.first = NULL; }
void condition_variable::notify_one() noexcept {
unsigned old_state = irq_disable();
priority_queue_node_t* head = priority_queue_remove_head(&m_queue);
int other_prio = -1;
if (head != NULL) {
thread_t* other_thread = (thread_t*)sched_threads[head->data];
if (other_thread) {
other_prio = other_thread->priority;
sched_set_status(other_thread, STATUS_PENDING);
}
head->data = -1u;
}
irq_restore(old_state);
if (other_prio >= 0) {
sched_switch(other_prio);
}
}
void condition_variable::notify_all() noexcept {
unsigned old_state = irq_disable();
int other_prio = -1;
while (true) {
priority_queue_node_t* head = priority_queue_remove_head(&m_queue);
if (head == NULL) {
break;
}
thread_t* other_thread = (thread_t*)sched_threads[head->data];
if (other_thread) {
auto max_prio
= [](int a, int b) { return (a < 0) ? b : ((a < b) ? a : b); };
other_prio = max_prio(other_prio, other_thread->priority);
sched_set_status(other_thread, STATUS_PENDING);
}
head->data = -1u;
}
irq_restore(old_state);
if (other_prio >= 0) {
sched_switch(other_prio);
}
}
void condition_variable::wait(unique_lock<mutex>& lock) noexcept {
priority_queue_node_t n;
n.priority = sched_active_thread->priority;
n.data = sched_active_pid;
n.next = NULL;
// the signaling thread may not hold the mutex, the queue is not thread safe
unsigned old_state = irq_disable();
priority_queue_add(&m_queue, &n);
irq_restore(old_state);
mutex_unlock_and_sleep(lock.mutex()->native_handle());
if (n.data != -1u) {
// on signaling n.data is set to -1u
// if it isn't set, then the wakeup is either spurious or a timer wakeup
old_state = irq_disable();
priority_queue_remove(&m_queue, &n);
irq_restore(old_state);
}
mutex_lock(lock.mutex()->native_handle());
}
cv_status condition_variable::wait_until(unique_lock<mutex>& lock,
const time_point& timeout_time) {
xtimer_t timer;
// todo: use function to wait for absolute timepoint once available
timex_t before;
xtimer_now_timex(&before);
auto diff = timex_sub(timeout_time.native_handle(), before);
xtimer_set_wakeup(&timer, timex_uint64(diff), sched_active_pid);
wait(lock);
timex_t after;
xtimer_now_timex(&after);
xtimer_remove(&timer);
auto cmp = timex_cmp(after, timeout_time.native_handle());
return cmp < 1 ? cv_status::no_timeout : cv_status::timeout;
}
} // namespace riot