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Commit 6add0aa9 authored by Dmitri Plotnikov's avatar Dmitri Plotnikov
Browse files

Lock BatteryUsageStats snapshot directory 

From documentation:
"File locks are held on behalf of the entire Java virtual machine.
They are not suitable for controlling access to a file by multiple threads within the same virtual machine."

This means that we should use two locks: one internal to system server,
and another cross-process.

Bug: 216454829
Test: atest FrameworksCoreTests:BatteryStatsTests
Change-Id: I7689ab91a0759f99da700383647f4f8a1fae4362
parent a2afb955

core/java/com/android/internal/os/BatteryUsageStatsStore.java

+46 −21
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ import android.os.BatteryUsageStats; 
import android.os.BatteryUsageStatsQuery;

import android.os.Handler;

import android.util.AtomicFile;

import android.util.Log;

import android.util.LongArray;

import android.util.Slog;

import android.util.TypedXmlPullParser;
@@ -47,6 +48,7 @@ import java.util.Locale; 
import java.util.Map;

import java.util.Properties;

import java.util.TreeMap;

import java.util.concurrent.locks.ReentrantLock;



/**

 * A storage mechanism for BatteryUsageStats snapshots.
@@ -73,6 +75,8 @@ public class BatteryUsageStatsStore { 
    private boolean mSystemReady;

    private final File mStoreDir;

    private final File mLockFile;

    private final ReentrantLock mFileLock = new ReentrantLock();

    private FileLock mJvmLock;

    private final AtomicFile mConfigFile;

    private final long mMaxStorageBytes;

    private final Handler mHandler;
@@ -120,11 +124,11 @@ public class BatteryUsageStatsStore { 
    }



    private void storeBatteryUsageStats(BatteryUsageStats stats) {

        try (FileLock lock = lockSnapshotDirectory()) {

        lockSnapshotDirectory();

        try {

            if (!mStoreDir.exists()) {

                if (!mStoreDir.mkdirs()) {

                    Slog.e(TAG,

                            "Could not create a directory for battery usage stats snapshots");

                    Slog.e(TAG, "Could not create a directory for battery usage stats snapshots");

                    return;

                }

            }
@@ -136,8 +140,8 @@ public class BatteryUsageStatsStore { 
            }



            removeOldSnapshotsLocked();

        } catch (IOException e) {

            Slog.e(TAG, "Cannot lock battery usage stats directory", e);

        } finally {

            unlockSnapshotDirectory();

        }

    }
@@ -147,7 +151,8 @@ public class BatteryUsageStatsStore { 
     */

    public long[] listBatteryUsageStatsTimestamps() {

        LongArray timestamps = new LongArray(100);

        try (FileLock lock = lockSnapshotDirectory()) {

        lockSnapshotDirectory();

        try {

            for (File file : mStoreDir.listFiles()) {

                String fileName = file.getName();

                if (fileName.endsWith(SNAPSHOT_FILE_EXTENSION)) {
@@ -161,8 +166,8 @@ public class BatteryUsageStatsStore { 
                    }

                }

            }

        } catch (IOException e) {

            Slog.e(TAG, "Cannot lock battery usage stats directory", e);

        } finally {

            unlockSnapshotDirectory();

        }

        return timestamps.toArray();

    }
@@ -173,15 +178,16 @@ public class BatteryUsageStatsStore { 
     */

    @Nullable

    public BatteryUsageStats loadBatteryUsageStats(long timestamp) {

        try (FileLock lock = lockSnapshotDirectory()) {

        lockSnapshotDirectory();

        try {

            File file = makeSnapshotFilename(timestamp);

            try {

                return readXmlFileLocked(file);

            } catch (Exception e) {

                Slog.e(TAG, "Cannot read battery usage stats", e);

            }

        } catch (IOException e) {

            Slog.e(TAG, "Cannot lock battery usage stats directory", e);

        } finally {

            unlockSnapshotDirectory();

        }

        return null;

    }
@@ -192,7 +198,8 @@ public class BatteryUsageStatsStore { 
     */

    public void setLastBatteryUsageStatsBeforeResetAtomPullTimestamp(long timestamp) {

        Properties props = new Properties();

        try (FileLock lock = lockSnapshotDirectory()) {

        lockSnapshotDirectory();

        try {

            try (InputStream in = mConfigFile.openRead()) {

                props.load(in);

            } catch (IOException e) {
@@ -209,8 +216,8 @@ public class BatteryUsageStatsStore { 
                mConfigFile.failWrite(out);

                Slog.e(TAG, "Cannot save config file " + mConfigFile, e);

            }

        } catch (IOException e) {

            Slog.e(TAG, "Cannot lock battery usage stats directory", e);

        } finally {

            unlockSnapshotDirectory();

        }

    }
@@ -220,23 +227,41 @@ public class BatteryUsageStatsStore { 
     */

    public long getLastBatteryUsageStatsBeforeResetAtomPullTimestamp() {

        Properties props = new Properties();

        try (FileLock lock = lockSnapshotDirectory()) {

        lockSnapshotDirectory();

        try {

            try (InputStream in = mConfigFile.openRead()) {

                props.load(in);

            } catch (IOException e) {

                Slog.e(TAG, "Cannot load config file " + mConfigFile, e);

            }

        } catch (IOException e) {

            Slog.e(TAG, "Cannot lock battery usage stats directory", e);

        } finally {

            unlockSnapshotDirectory();

        }

        return Long.parseLong(

                props.getProperty(BATTERY_USAGE_STATS_BEFORE_RESET_TIMESTAMP_PROPERTY, "0"));

    }



    private FileLock lockSnapshotDirectory() throws IOException {

    private void lockSnapshotDirectory() {

        mFileLock.lock();



        // Lock the directory from access by other JVMs

        try {

            mLockFile.getParentFile().mkdirs();

            mLockFile.createNewFile();

        return FileChannel.open(mLockFile.toPath(), StandardOpenOption.WRITE).lock();

            mJvmLock = FileChannel.open(mLockFile.toPath(), StandardOpenOption.WRITE).lock();

        } catch (IOException e) {

            Log.e(TAG, "Cannot lock snapshot directory", e);

        }

    }



    private void unlockSnapshotDirectory() {

        try {

            mJvmLock.close();

        } catch (IOException e) {

            Log.e(TAG, "Cannot unlock snapshot directory", e);

        } finally {

            mFileLock.unlock();

        }

    }



    /**