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Commit 1ea62c98 authored by Ytai Ben-Tsvi's avatar Ytai Ben-Tsvi
Browse files

Modernize TimeCheck 

This replaces the usage of Thread, Mutex, Condition and KeyedVector
with their std:: counterparts.

We're also extracting the time thread from TimeCheck and adding a unit
test.

The logic in TimerThread now is easier to follow and it is more
evident that tasks would never be executed before their deadline
arrived. In the original code, this wasn't obvious.

Test: atest libmediautils_test
Bug: 188748333
Change-Id: Iac887e7d6e6758c0a0e5c56695e9671082e64b09
parent 197acd5e

media/utils/Android.bp

+10 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ cc_library { 
        "SchedulingPolicyService.cpp",

        "ServiceUtilities.cpp",

        "TimeCheck.cpp",

        "TimerThread.cpp",

    ],

    static_libs: [

        "libc_malloc_debug_backtrace",
@@ -118,3 +119,12 @@ cc_library_headers { 


    export_include_dirs: ["include"],

}



cc_test {

    name: "libmediautils_test",

    srcs: ["TimerThread-test.cpp"],

    shared_libs: [

      "libmediautils",

      "libutils",

    ]

}

media/utils/TimeCheck.cpp

+25 −72
Original line number Diff line number Diff line
@@ -16,9 +16,11 @@ 


#define LOG_TAG "TimeCheck"



#include <utils/Log.h>

#include <mediautils/TimeCheck.h>

#include <optional>



#include <mediautils/EventLog.h>

#include <mediautils/TimeCheck.h>

#include <utils/Log.h>

#include "debuggerd/handler.h"



namespace android {
@@ -58,67 +60,21 @@ std::vector<pid_t> TimeCheck::getAudioHalPids() { 
}



/* static */

sp<TimeCheck::TimeCheckThread> TimeCheck::getTimeCheckThread()

{

    static sp<TimeCheck::TimeCheckThread> sTimeCheckThread = new TimeCheck::TimeCheckThread();

TimerThread* TimeCheck::getTimeCheckThread() {

    static TimerThread* sTimeCheckThread = new TimerThread();

    return sTimeCheckThread;

}



TimeCheck::TimeCheck(const char* tag, uint32_t timeoutMs)

    : mEndTimeNs(getTimeCheckThread()->startMonitoring(tag, timeoutMs))

{

}

    : mTimerHandle(getTimeCheckThread()->scheduleTask([tag] { crash(tag); },

                                                      std::chrono::milliseconds(timeoutMs))) {}



TimeCheck::~TimeCheck() {

    getTimeCheckThread()->stopMonitoring(mEndTimeNs);

    getTimeCheckThread()->cancelTask(mTimerHandle);

}



TimeCheck::TimeCheckThread::~TimeCheckThread()

{

    AutoMutex _l(mMutex);

    requestExit();

    mMonitorRequests.clear();

    mCond.signal();

}



nsecs_t TimeCheck::TimeCheckThread::startMonitoring(const char *tag, uint32_t timeoutMs) {

    Mutex::Autolock _l(mMutex);

    nsecs_t endTimeNs = systemTime() + milliseconds(timeoutMs);

    for (; mMonitorRequests.indexOfKey(endTimeNs) >= 0; ++endTimeNs);

    mMonitorRequests.add(endTimeNs, tag);

    mCond.signal();

    return endTimeNs;

}



void TimeCheck::TimeCheckThread::stopMonitoring(nsecs_t endTimeNs) {

    Mutex::Autolock _l(mMutex);

    mMonitorRequests.removeItem(endTimeNs);

    mCond.signal();

}



bool TimeCheck::TimeCheckThread::threadLoop()

{

    status_t status = TIMED_OUT;

    {

        AutoMutex _l(mMutex);



        if (exitPending()) {

            return false;

        }



        nsecs_t endTimeNs = INT64_MAX;

        const char *tag = "<unspecified>";

        // KeyedVector mMonitorRequests is ordered so take first entry as next timeout

        if (mMonitorRequests.size() != 0) {

            endTimeNs = mMonitorRequests.keyAt(0);

            tag = mMonitorRequests.valueAt(0);

        }



        const nsecs_t waitTimeNs = endTimeNs - systemTime();

        if (waitTimeNs > 0) {

            status = mCond.waitRelative(mMutex, waitTimeNs);

        }

        if (status != NO_ERROR) {

/* static */

void TimeCheck::crash(const char* tag) {

    // Generate audio HAL processes tombstones and allow time to complete

    // before forcing restart

    std::vector<pid_t> pids = getAudioHalPids();
@@ -134,8 +90,5 @@ bool TimeCheck::TimeCheckThread::threadLoop() 
    LOG_EVENT_STRING(LOGTAG_AUDIO_BINDER_TIMEOUT, tag);

    LOG_ALWAYS_FATAL("TimeCheck timeout for %s", tag);

}

    }

    return true;

}



};  // namespace android

media/utils/TimerThread-test.cpp

0 → 100644
+146 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2021 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 <chrono>

#include <thread>

#include <gtest/gtest.h>

#include <mediautils/TimerThread.h>



using namespace std::chrono_literals;



namespace android {

namespace {



constexpr auto kJitter = 10ms;



TEST(TimerThread, Basic) {

    std::atomic<bool> taskRan = false;

    TimerThread thread;

    thread.scheduleTask([&taskRan] { taskRan = true; }, 100ms);

    std::this_thread::sleep_for(100ms - kJitter);

    ASSERT_FALSE(taskRan);

    std::this_thread::sleep_for(2 * kJitter);

    ASSERT_TRUE(taskRan);

}



TEST(TimerThread, Cancel) {

    std::atomic<bool> taskRan = false;

    TimerThread thread;

    TimerThread::Handle handle = thread.scheduleTask([&taskRan] { taskRan = true; }, 100ms);

    std::this_thread::sleep_for(100ms - kJitter);

    ASSERT_FALSE(taskRan);

    thread.cancelTask(handle);

    std::this_thread::sleep_for(2 * kJitter);

    ASSERT_FALSE(taskRan);

}



TEST(TimerThread, CancelAfterRun) {

    std::atomic<bool> taskRan = false;

    TimerThread thread;

    TimerThread::Handle handle = thread.scheduleTask([&taskRan] { taskRan = true; }, 100ms);

    std::this_thread::sleep_for(100ms + kJitter);

    ASSERT_TRUE(taskRan);

    thread.cancelTask(handle);

}



TEST(TimerThread, MultipleTasks) {

    std::array<std::atomic<bool>, 6> taskRan;

    TimerThread thread;



    auto startTime = std::chrono::steady_clock::now();



    thread.scheduleTask([&taskRan] { taskRan[0] = true; }, 300ms);

    thread.scheduleTask([&taskRan] { taskRan[1] = true; }, 100ms);

    thread.scheduleTask([&taskRan] { taskRan[2] = true; }, 200ms);

    thread.scheduleTask([&taskRan] { taskRan[3] = true; }, 400ms);

    auto handle4 = thread.scheduleTask([&taskRan] { taskRan[4] = true; }, 200ms);

    thread.scheduleTask([&taskRan] { taskRan[5] = true; }, 200ms);



    // Task 1 should trigger around 100ms.

    std::this_thread::sleep_until(startTime + 100ms - kJitter);

    ASSERT_FALSE(taskRan[0]);

    ASSERT_FALSE(taskRan[1]);

    ASSERT_FALSE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_FALSE(taskRan[5]);



    std::this_thread::sleep_until(startTime + 100ms + kJitter);

    ASSERT_FALSE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_FALSE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_FALSE(taskRan[5]);



    // Cancel task 4 before it gets a chance to run.

    thread.cancelTask(handle4);



    // Tasks 2 and 5 should trigger around 200ms.

    std::this_thread::sleep_until(startTime + 200ms - kJitter);

    ASSERT_FALSE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_FALSE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_FALSE(taskRan[5]);



    std::this_thread::sleep_until(startTime + 200ms + kJitter);

    ASSERT_FALSE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_TRUE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_TRUE(taskRan[5]);



    // Task 0 should trigger around 300ms.

    std::this_thread::sleep_until(startTime + 300ms - kJitter);

    ASSERT_FALSE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_TRUE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_TRUE(taskRan[5]);



    std::this_thread::sleep_until(startTime + 300ms + kJitter);

    ASSERT_TRUE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_TRUE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_TRUE(taskRan[5]);



    // Task 3 should trigger around 400ms.

    std::this_thread::sleep_until(startTime + 400ms - kJitter);

    ASSERT_TRUE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_TRUE(taskRan[2]);

    ASSERT_FALSE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_TRUE(taskRan[5]);



    std::this_thread::sleep_until(startTime + 400ms + kJitter);

    ASSERT_TRUE(taskRan[0]);

    ASSERT_TRUE(taskRan[1]);

    ASSERT_TRUE(taskRan[2]);

    ASSERT_TRUE(taskRan[3]);

    ASSERT_FALSE(taskRan[4]);

    ASSERT_TRUE(taskRan[5]);

}





}  // namespace

}  // namespace android

media/utils/TimerThread.cpp

0 → 100644
+76 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2021 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.

 */



#define LOG_TAG "TimerThread"



#include <optional>



#include <mediautils/TimerThread.h>

#include <utils/ThreadDefs.h>



namespace android {



TimerThread::TimerThread() : mThread([this] { threadFunc(); }) {

    pthread_setname_np(mThread.native_handle(), "TimeCheckThread");

    pthread_setschedprio(mThread.native_handle(), PRIORITY_URGENT_AUDIO);

}



TimerThread::~TimerThread() {

    {

        std::lock_guard _l(mMutex);

        mShouldExit = true;

        mCond.notify_all();

    }

    mThread.join();

}



TimerThread::Handle TimerThread::scheduleTaskAtDeadline(std::function<void()>&& func,

                                                        TimePoint deadline) {

    std::lock_guard _l(mMutex);



    // To avoid key collisions, advance by 1 tick until the key is unique.

    for (; mMonitorRequests.find(deadline) != mMonitorRequests.end();

         deadline += TimePoint::duration(1))

        ;

    mMonitorRequests.emplace(deadline, std::move(func));

    mCond.notify_all();

    return deadline;

}



void TimerThread::cancelTask(Handle handle) {

    std::lock_guard _l(mMutex);

    mMonitorRequests.erase(handle);

}



void TimerThread::threadFunc() {

    std::unique_lock _l(mMutex);



    while (!mShouldExit) {

        if (!mMonitorRequests.empty()) {

            TimePoint nextDeadline = mMonitorRequests.begin()->first;

            if (nextDeadline < std::chrono::steady_clock::now()) {

                // Deadline expired.

                mMonitorRequests.begin()->second();

                mMonitorRequests.erase(mMonitorRequests.begin());

            }

            mCond.wait_until(_l, nextDeadline);

        } else {

            mCond.wait(_l);

        }

    }

}



}  // namespace android

media/utils/include/mediautils/TimeCheck.h

+13 −42
Original line number Diff line number Diff line
@@ -14,14 +14,12 @@ 
 * limitations under the License.

 */



#pragma once



#ifndef ANDROID_TIME_CHECK_H

#define ANDROID_TIME_CHECK_H



#include <utils/KeyedVector.h>

#include <utils/Thread.h>

#include <vector>



#include <mediautils/TimerThread.h>



namespace android {



// A class monitoring execution time for a code block (scoped variable) and causing an assert
@@ -29,7 +27,6 @@ namespace android { 


class TimeCheck {

  public:



    // The default timeout is chosen to be less than system server watchdog timeout

    static constexpr uint32_t kDefaultTimeOutMs = 5000;
@@ -39,37 +36,11 @@ public: 
    static std::vector<pid_t> getAudioHalPids();



  private:



    class TimeCheckThread : public Thread {

    public:



                            TimeCheckThread() {}

        virtual             ~TimeCheckThread() override;



                nsecs_t     startMonitoring(const char *tag, uint32_t timeoutMs);

                void        stopMonitoring(nsecs_t endTimeNs);



    private:



                // RefBase

        virtual void        onFirstRef() override { run("TimeCheckThread", PRIORITY_URGENT_AUDIO); }



                // Thread

        virtual bool        threadLoop() override;



                Condition           mCond;

                Mutex               mMutex;

                // using the end time in ns as key is OK given the risk is low that two entries

                // are added in such a way that <add time> + <timeout> are the same for both.

                KeyedVector< nsecs_t, const char*>  mMonitorRequests;

    };



    static sp<TimeCheckThread> getTimeCheckThread();

    static TimerThread* getTimeCheckThread();

    static void accessAudioHalPids(std::vector<pid_t>* pids, bool update);

    static void crash(const char* tag);



    const           nsecs_t mEndTimeNs;

    const TimerThread::Handle mTimerHandle;

};



};  // namespace android
 


#endif  // ANDROID_TIME_CHECK_H