Android的离奇陷阱 — 设置线程优先级导致的微信卡顿惨案

Thread t = new Thread();t.start();t.setPriority(3);

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long startTime = System.currentTimeMillis();Thread.sleep(10);Log.i("Matrix","duration = " + (System.currentTimeMillis() - startTime));//结果为：duration = 50

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Thread t = new Thread();t.start();t.setPriority(3);
long startTime = System.currentTimeMillis();Thread.sleep(10);Log.i("Matrix","duration = " + (System.currentTimeMillis() - startTime));  // 结果为duration = 50ms

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palette_status_t PaletteSchedSetPriority(int32_t tid, int32_t managed_priority) {    if (managed_priority < art::palette::kMinManagedThreadPriority ||        managed_priority > art::palette::kMaxManagedThreadPriority) {        return PALETTE_STATUS_INVALID_ARGUMENT;    }    int new_nice = kNiceValues[managed_priority - art::palette::kMinManagedThreadPriority];     int curr_nice = getpriority(PRIO_PROCESS, tid);
    if (curr_nice == new_nice) {        return PALETTE_STATUS_OK;    }
    if (new_nice >= ANDROID_PRIORITY_BACKGROUND) {        SetTaskProfiles(tid, {"SCHED_SP_BACKGROUND"}, true);    } else if (curr_nice >= ANDROID_PRIORITY_BACKGROUND) {        SchedPolicy policy;        // Change to the sched policy group of the process.        if (get_sched_policy(getpid(), &policy) != 0) {            policy = SP_FOREGROUND;        }        SetTaskProfiles(tid, {get_sched_policy_profile_name(policy)}, true);    }
    if (setpriority(PRIO_PROCESS, tid, new_nice) != 0) {        return PALETTE_STATUS_CHECK_ERRNO;    }    return PALETTE_STATUS_OK;}
static const int kNiceValues[art::palette::kNumManagedThreadPriorities] = {    ANDROID_PRIORITY_LOWEST, // 1 (MIN_PRIORITY)    ANDROID_PRIORITY_BACKGROUND + 6,    ANDROID_PRIORITY_BACKGROUND + 3,    ANDROID_PRIORITY_BACKGROUND,    ANDROID_PRIORITY_NORMAL, // 5 (NORM_PRIORITY)    ANDROID_PRIORITY_NORMAL - 2,    ANDROID_PRIORITY_NORMAL - 4,    ANDROID_PRIORITY_URGENT_DISPLAY + 3,    ANDROID_PRIORITY_URGENT_DISPLAY + 2,    ANDROID_PRIORITY_URGENT_DISPLAY // 10 (MAX_PRIORITY)};

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bool SetTaskProfiles(int tid, const std::vector<:string>& profiles, bool use_fd_cache) {    return TaskProfiles::GetInstance().SetTaskProfiles(tid, profiles, use_fd_cache);}
TaskProfiles::TaskProfiles() {    // load system task profiles    if (!Load(CgroupMap::GetInstance(), TASK_PROFILE_DB_FILE)) {        LOG(ERROR) << "Loading " << TASK_PROFILE_DB_FILE << " for [" << getpid() << "] failed";    }    //省略...... } 
static constexpr const char* TASK_PROFILE_DB_FILE = "/etc/task_profiles.json";

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{    "Name": "SCHED_SP_BACKGROUND",    "Profiles": [ "HighEnergySaving", "LowIoPriority", "TimerSlackHigh" ]}

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    {      "Name": "TimerSlackHigh",      "Actions": [        {          "Name": "SetTimerSlack",          "Params":          {            "Slack": "40000000"          }        }      ]    },    {      "Name": "TimerSlackNormal",      "Actions": [        {          "Name": "SetTimerSlack",          "Params":          {            "Slack": "50000"          }        }      ]    }

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void Thread::SetNativePriority(int new_priority) {    palette_status_t status = PaletteSchedSetPriority(GetTid(), new_priority);    CHECK(status == PALETTE_STATUS_OK || status == PALETTE_STATUS_CHECK_ERRNO);}

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pid_t GetTid() const {    return tls32_.tid;}

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void Thread::InitTid() {    tls32_.tid = ::art::GetTid();}
bool Thread::Init(ThreadList* thread_list, JavaVMExt* java_vm, JNIEnvExt* jni_env_ext) {    //......    InitTid();    //......}
void* Thread::CreateCallback(void* arg) {    //......    CHECK(self->Init(runtime->GetThreadList(), runtime->GetJavaVM(), self->tlsPtr_.tmp_jni_env));    //......}
void Thread::CreateNativeThread(JNIEnv* env, jobject java_peer, size_t stack_size, bool is_daemon) {    //......    pthread_create_result = pthread_create(&new_pthread,                                           &attr,                                           Thread::CreateCallback,                                           child_thread);    //......}

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bool SetTimerSlackAction::ExecuteForTask(int tid) const {    //......    if (tid == 0 || tid == GetThreadId()) {        if (prctl(PR_SET_TIMERSLACK, slack_) == -1) {            PLOG(ERROR) << "set_timerslack_ns prctl failed";        }    }
    return true;}

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 Thread t = new Thread(); t.start(); t.setPriority(3);
 long startTime = System.currentTimeMillis(); Thread.sleep(10); Log.i("Matrix","duration = " + (System.currentTimeMillis() - startTime));

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Thread t = new Thread();t.start();t.setPriority(3);
long startTime = System.currentTimeMillis();Thread.sleep(10);Log.i("Matrix","MainThread duration = " + (System.currentTimeMillis() - startTime));  //结果为50
new Thread(new Runnable() {    @Override    public void run() {        long startTime = System.currentTimeMillis();        Thread.sleep(10);        Log.i("Matrix","Thread duration = " + (System.currentTimeMillis() - startTime));          //结果为10    }}).start();

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void* Thread::CreateCallback(void* arg) {    //......    ArtField* priorityField =         jni::DecodeArtField(WellKnownClasses::java_lang_Thread_priority);    self->SetNativePriority(priorityField->GetInt(self->tlsPtr_.opeer));    //......}

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Thread t = new Thread();t.start();t.setPriority(3);
long startTime = System.currentTimeMillis();Thread.sleep(10);Log.i("Matrix","MainThread duration = " + (System.currentTimeMillis() - startTime));  //结果为50
new WebView(context);
new Thread(new Runnable() {    @Override    public void run() {        long startTime = System.currentTimeMillis();        Thread.sleep(10);        Log.i("Matrix","Thread duration = " + (System.currentTimeMillis() - startTime));          //结果为50    }}).start();

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// Up the priority of the UI thread unless it was already high (since Mac// and recent versions of Android (O+) do this automatically).if (base::FeatureList::IsEnabled(    features::kBrowserUseDisplayThreadPriority) &&    base::PlatformThread::GetCurrentThreadPriority() <          base::ThreadPriority::DISPLAY) {    base::PlatformThread::SetCurrentThreadPriority(        base::ThreadPriority::DISPLAY);}

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if (new_nice >= ANDROID_PRIORITY_BACKGROUND) {    SetTaskProfiles(tid, {"SCHED_SP_BACKGROUND"}, true);} else if (curr_nice >= ANDROID_PRIORITY_BACKGROUND) {    SchedPolicy policy;    // Change to the sched policy group of the process.    if (get_sched_policy(getpid(), &policy) != 0) {        policy = SP_FOREGROUND;    }    SetTaskProfiles(tid, {get_sched_policy_profile_name(policy)}, true);}

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int (*original_setpriority)(int __which, id_t __who, int __priority);
int my_setpriority(int __which, id_t __who, int __priority) {        if (__priority <= 0) {        return original_setpriority(__which, __who, __priority);    }        if (__who == 0 && getpid() == gettid()) {        // Throw Crash Here    } else if (__who == getpid()) {        // Throw Crash Here    }
    return original_setpriority(__which, __who, __priority);}

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int (*original_prctl)(int option, unsigned long arg2, unsigned long arg3,              unsigned long arg4, unsigned long arg5);
int my_prctl(int option, unsigned long arg2, unsigned long arg3,             unsigned long arg4, unsigned long arg5) {    if(option == PR_SET_TIMERSLACK) {        if (gettid()==getpid() && arg2 > 50000) {            // Throw Crash Here        }    }    return original_prctl(option, arg2, arg3, arg4, arg5);}

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HandlerThread ht = new HandlerThread("leafjia-thread");ht.setPriority(3);ht.start();

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public class HandlerThread extends Thread {    int mPriority;    //......        public HandlerThread(String name) {        super(name);        mPriority = Process.THREAD_PRIORITY_DEFAULT;    }        public HandlerThread(String name, int priority) {        super(name);        mPriority = priority;    }
    //......
    @Override    public void run() {        mTid = Process.myTid();        Looper.prepare();        synchronized (this) {            mLooper = Looper.myLooper();            notifyAll();        }        Process.setThreadPriority(mPriority);        onLooperPrepared();        Looper.loop();        mTid = -1;    }    //......}

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HandlerThread ht = new HandlerThread("My-Thread", 13);ht.start();

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//Case1: 正确，thread线程的nice值被设置为13Thread thread = new Thread();thread.setPriority(3);thread.start();
//Case2: 正确，thread线程的nice值被设置为13Thread thread = new Thread(new Runnable() {    @Override    public void run() {        Thread.currentThread().setPriority(3);        // 或：        // Process.setThreadPriority(13);    }});thread.start();
//Case3: 错误，thread线程的nice值一定被设置为13//（可能直接被设置或从当前线程继承而来，视时序而定），// 当前线程的nice值很有可能被设置为13Thread thread = new Thread();thread.start();thread.setPriority(3);
//Case4: 错误，同上HandlerThread thread = new HandlerThread("My-Thread");thread.start();thread.setPriority(3);
//Case5: 错误，thread线程的nice值被设置为默认的0HandlerThread thread = new HandlerThread("My-Thread");thread.setPriority(3);thread.start();
//Case6: 正确，thread线程的nice值被设置为13HandlerThread thread = new HandlerThread("My-Thread", 13);thread.start();

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