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/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "OneShotTimer.h"
#include <utils/Log.h>
#include <utils/Timers.h>
#include <chrono>
#include <sstream>
#include <thread>
namespace {
using namespace std::chrono_literals;
constexpr int64_t kNsToSeconds = std::chrono::duration_cast<std::chrono::nanoseconds>(1s).count();
// The syscall interface uses a pair of integers for the timestamp. The first
// (tv_sec) is the whole count of seconds. The second (tv_nsec) is the
// nanosecond part of the count. This function takes care of translation.
void calculateTimeoutTime(std::chrono::nanoseconds timestamp, timespec* spec) {
const nsecs_t timeout = systemTime(CLOCK_MONOTONIC) + timestamp.count();
spec->tv_sec = static_cast<__kernel_time_t>(timeout / kNsToSeconds);
spec->tv_nsec = timeout % kNsToSeconds;
}
} // namespace
namespace android {
namespace scheduler {
OneShotTimer::OneShotTimer(std::string name, const Interval& interval,
const ResetCallback& resetCallback,
const TimeoutCallback& timeoutCallback, std::unique_ptr<Clock> clock)
: mClock(std::move(clock)),
mName(std::move(name)),
mInterval(interval),
mResetCallback(resetCallback),
mTimeoutCallback(timeoutCallback) {
mLastResetTime = std::chrono::steady_clock::time_point::min();
LOG_ALWAYS_FATAL_IF(!mClock, "Clock must not be provided");
}
OneShotTimer::~OneShotTimer() {
stop();
}
void OneShotTimer::start() {
int result = sem_init(&mSemaphore, 0, 0);
LOG_ALWAYS_FATAL_IF(result, "sem_init failed");
if (!mThread.joinable()) {
// Only create thread if it has not been created.
mThread = std::thread(&OneShotTimer::loop, this);
}
}
void OneShotTimer::stop() {
mStopTriggered = true;
int result = sem_post(&mSemaphore);
LOG_ALWAYS_FATAL_IF(result, "sem_post failed");
if (mThread.joinable()) {
mThread.join();
result = sem_destroy(&mSemaphore);
LOG_ALWAYS_FATAL_IF(result, "sem_destroy failed");
}
}
void OneShotTimer::loop() {
if (pthread_setname_np(pthread_self(), mName.c_str())) {
ALOGW("Failed to set thread name on dispatch thread");
}
TimerState state = TimerState::RESET;
while (true) {
bool triggerReset = false;
bool triggerTimeout = false;
state = checkForResetAndStop(state);
if (state == TimerState::STOPPED) {
break;
}
if (state == TimerState::IDLE) {
int result = sem_wait(&mSemaphore);
if (result && errno != EINTR) {
std::stringstream ss;
ss << "sem_wait failed (" << errno << ")";
LOG_ALWAYS_FATAL("%s", ss.str().c_str());
}
continue;
}
if (state == TimerState::RESET) {
triggerReset = true;
}
if (triggerReset && mResetCallback) {
mResetCallback();
}
state = checkForResetAndStop(state);
if (state == TimerState::STOPPED) {
break;
}
auto triggerTime = mClock->now() + mInterval;
state = TimerState::WAITING;
while (true) {
// Wait until triggerTime time to check if we need to reset or drop into the idle state.
if (const auto triggerInterval = triggerTime - mClock->now(); triggerInterval > 0ns) {
mWaiting = true;
struct timespec ts;
calculateTimeoutTime(triggerInterval, &ts);
int result = sem_clockwait(&mSemaphore, CLOCK_MONOTONIC, &ts);
if (result && errno != ETIMEDOUT && errno != EINTR) {
std::stringstream ss;
ss << "sem_clockwait failed (" << errno << ")";
LOG_ALWAYS_FATAL("%s", ss.str().c_str());
}
}
mWaiting = false;
state = checkForResetAndStop(state);
if (state == TimerState::STOPPED) {
break;
}
if (state == TimerState::WAITING && (triggerTime - mClock->now()) <= 0ns) {
triggerTimeout = true;
state = TimerState::IDLE;
break;
}
if (state == TimerState::RESET) {
triggerTime = mLastResetTime.load() + mInterval;
state = TimerState::WAITING;
}
}
if (triggerTimeout && mTimeoutCallback) {
mTimeoutCallback();
}
}
}
OneShotTimer::TimerState OneShotTimer::checkForResetAndStop(TimerState state) {
// Stop takes precedence of the reset.
if (mStopTriggered.exchange(false)) {
return TimerState::STOPPED;
}
// If the state was stopped, the thread was joined, and we cannot reset
// the timer anymore.
if (state != TimerState::STOPPED && mResetTriggered.exchange(false)) {
return TimerState::RESET;
}
return state;
}
void OneShotTimer::reset() {
mLastResetTime = mClock->now();
mResetTriggered = true;
// If mWaiting is true, then we are guaranteed to be in a block where we are waiting on
// mSemaphore for a timeout, rather than idling. So we can avoid a sem_post call since we can
// just check that we triggered a reset on timeout.
if (!mWaiting) {
LOG_ALWAYS_FATAL_IF(sem_post(&mSemaphore), "sem_post failed");
}
}
} // namespace scheduler
} // namespace android
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