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Commit 304ee7b8 authored by Kweku Adams's avatar Kweku Adams
Browse files

Fixing deadlock in OomAdjProfiler. 

During dumping, the ActivityManager lock is held. If a CPU time update
was scheduled before a dump but the background thread was working on a
task that required the ActivityManager lock, OomAdjProfiler would wait
indefinitely for the update in the dump() method because the AM lock is
already taken in the main thread. Removing the wait and updating the CPU
time in the main thread during dumping only should avoid the potential
deadlock.

Bug: 130635979
Test: adb shell dumpsys activity
Change-Id: Ibafe79b46babe16f589ec28d525174f9a01f00b8
parent 3f8cdda0

services/core/java/com/android/server/am/OomAdjProfiler.java

+26 −35
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 


package com.android.server.am;



import android.os.Message;

import android.os.PowerManagerInternal;

import android.os.Process;

import android.os.SystemClock;
@@ -29,14 +30,20 @@ import com.android.internal.util.function.pooled.PooledLambda; 
import java.io.PrintWriter;



public class OomAdjProfiler {

    // Disable profiling for Q. Re-enable once b/130635979 is fixed.

    private static final boolean PROFILING_DISABLED = true;

    private static final int MSG_UPDATE_CPU_TIME = 42;



    @GuardedBy("this")

    private boolean mOnBattery;

    @GuardedBy("this")

    private boolean mScreenOff;



    /** The value of {@link #mOnBattery} when the CPU time update was last scheduled. */

    @GuardedBy("this")

    private boolean mLastScheduledOnBattery;

    /** The value of {@link #mScreenOff} when the CPU time update was last scheduled. */

    @GuardedBy("this")

    private boolean mLastScheduledScreenOff;



    @GuardedBy("this")

    private long mOomAdjStartTimeMs;

    @GuardedBy("this")
@@ -59,9 +66,6 @@ public class OomAdjProfiler { 
    final RingBuffer<CpuTimes> mSystemServerCpuTimesHist = new RingBuffer<>(CpuTimes.class, 10);



    void batteryPowerChanged(boolean onBattery) {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            scheduleSystemServerCpuTimeUpdate();

            mOnBattery = onBattery;
@@ -69,9 +73,6 @@ public class OomAdjProfiler { 
    }



    void onWakefulnessChanged(int wakefulness) {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            scheduleSystemServerCpuTimeUpdate();

            mScreenOff = wakefulness != PowerManagerInternal.WAKEFULNESS_AWAKE;
@@ -79,9 +80,6 @@ public class OomAdjProfiler { 
    }



    void oomAdjStarted() {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            mOomAdjStartTimeMs = SystemClock.currentThreadTimeMillis();

            mOomAdjStarted = true;
@@ -89,9 +87,6 @@ public class OomAdjProfiler { 
    }



    void oomAdjEnded() {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            if (!mOomAdjStarted) {

                return;
@@ -101,31 +96,33 @@ public class OomAdjProfiler { 
    }



    private void scheduleSystemServerCpuTimeUpdate() {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            if (mSystemServerCpuTimeUpdateScheduled) {

                return;

            }

            mLastScheduledOnBattery = mOnBattery;

            mLastScheduledScreenOff = mScreenOff;

            mSystemServerCpuTimeUpdateScheduled = true;

            BackgroundThread.getHandler().sendMessage(PooledLambda.obtainMessage(

            Message scheduledMessage = PooledLambda.obtainMessage(

                    OomAdjProfiler::updateSystemServerCpuTime,

                    this, mOnBattery, mScreenOff));

                    this, mLastScheduledOnBattery, mLastScheduledScreenOff, true);

            scheduledMessage.setWhat(MSG_UPDATE_CPU_TIME);



            BackgroundThread.getHandler().sendMessage(scheduledMessage);

        }

    }



    private void updateSystemServerCpuTime(boolean onBattery, boolean screenOff) {

        if (PROFILING_DISABLED) {

            return;

        }

    private void updateSystemServerCpuTime(boolean onBattery, boolean screenOff,

            boolean onlyIfScheduled) {

        final long cpuTimeMs = mProcessCpuTracker.getCpuTimeForPid(Process.myPid());

        synchronized (this) {

            if (onlyIfScheduled && !mSystemServerCpuTimeUpdateScheduled) {

                return;

            }

            mSystemServerCpuTime.addCpuTimeMs(

                    cpuTimeMs - mLastSystemServerCpuTimeMs, onBattery, screenOff);

            mLastSystemServerCpuTimeMs = cpuTimeMs;

            mSystemServerCpuTimeUpdateScheduled = false;

            notifyAll();

        }

    }
@@ -142,20 +139,14 @@ public class OomAdjProfiler { 
    }



    void dump(PrintWriter pw) {

        if (PROFILING_DISABLED) {

            return;

        }

        synchronized (this) {

            if (mSystemServerCpuTimeUpdateScheduled) {

                while (mSystemServerCpuTimeUpdateScheduled) {

                    try {

                        wait();

                    } catch (InterruptedException e) {

                        Thread.currentThread().interrupt();

                    }

                }

                // Cancel the scheduled update since we're going to update it here instead.

                BackgroundThread.getHandler().removeMessages(MSG_UPDATE_CPU_TIME);

                // Make sure the values are attributed to the right states.

                updateSystemServerCpuTime(mLastScheduledOnBattery, mLastScheduledScreenOff, false);

            } else {

                updateSystemServerCpuTime(mOnBattery, mScreenOff);

                updateSystemServerCpuTime(mOnBattery, mScreenOff, false);

            }



            pw.println("System server and oomAdj runtimes (ms) in recent battery sessions "