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Commit ffe74357 authored by Philip P. Moltmann's avatar Philip P. Moltmann
Browse files

Make SharedPreferences check with higher precision 

When two processes modify shared preferences we use the timestamp to
figure out if the file was changes underneath. Do this with the highest
precision available (instead of sec) as before.

It would be possible to make the check more reliable by writing a unique
id to the shared pref file, but this would make this check much more
expensive in the common case that nothing changed. Considering that this
has not been a problem and we don't officially give any guarantee for
this sounds like a good middle-ground.

Change-Id: I04c96b6a946618d5599c26410c88d7cd654d31fb
Test: SharedPreferencesTest
Fixes: 62949739
parent 3779fb5f

core/java/android/app/SharedPreferencesImpl.java

+9 −8
Original line number Original line Diff line number Diff line
@@ -23,16 +23,19 @@ import android.os.Looper; 
import android.system.ErrnoException;

import android.system.ErrnoException;

import android.system.Os;

import android.system.Os;

import android.system.StructStat;

import android.system.StructStat;

import android.system.StructTimespec;

import android.util.Log;

import android.util.Log;





import com.google.android.collect.Maps;



import com.android.internal.annotations.GuardedBy;

import com.android.internal.annotations.GuardedBy;

import com.android.internal.util.ExponentiallyBucketedHistogram;

import com.android.internal.util.ExponentiallyBucketedHistogram;

import com.android.internal.util.XmlUtils;

import com.android.internal.util.XmlUtils;





import dalvik.system.BlockGuard;

import dalvik.system.BlockGuard;





import libcore.io.IoUtils;



import com.google.android.collect.Maps;



import org.xmlpull.v1.XmlPullParserException;

import org.xmlpull.v1.XmlPullParserException;





import java.io.BufferedInputStream;

import java.io.BufferedInputStream;
@@ -50,8 +53,6 @@ import java.util.Set; 
import java.util.WeakHashMap;

import java.util.WeakHashMap;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.CountDownLatch;





import libcore.io.IoUtils;



final class SharedPreferencesImpl implements SharedPreferences {

final class SharedPreferencesImpl implements SharedPreferences {

    private static final String TAG = "SharedPreferencesImpl";

    private static final String TAG = "SharedPreferencesImpl";

    private static final boolean DEBUG = false;

    private static final boolean DEBUG = false;
@@ -80,7 +81,7 @@ final class SharedPreferencesImpl implements SharedPreferences { 
    private boolean mLoaded = false;

    private boolean mLoaded = false;





    @GuardedBy("mLock")

    @GuardedBy("mLock")

    private long mStatTimestamp;

    private StructTimespec mStatTimestamp;





    @GuardedBy("mLock")

    @GuardedBy("mLock")

    private long mStatSize;

    private long mStatSize;
@@ -162,7 +163,7 @@ final class SharedPreferencesImpl implements SharedPreferences { 
            mLoaded = true;

            mLoaded = true;

            if (map != null) {

            if (map != null) {

                mMap = map;

                mMap = map;

                mStatTimestamp = stat.st_mtime;

                mStatTimestamp = stat.st_mtim;

                mStatSize = stat.st_size;

                mStatSize = stat.st_size;

            } else {

            } else {

                mMap = new HashMap<>();

                mMap = new HashMap<>();
@@ -209,7 +210,7 @@ final class SharedPreferencesImpl implements SharedPreferences { 
        }

        }





        synchronized (mLock) {

        synchronized (mLock) {

            return mStatTimestamp != stat.st_mtime || mStatSize != stat.st_size;

            return !stat.st_mtim.equals(mStatTimestamp) || mStatSize != stat.st_size;

        }

        }

    }

    }
@@ -744,7 +745,7 @@ final class SharedPreferencesImpl implements SharedPreferences { 
            try {

            try {

                final StructStat stat = Os.stat(mFile.getPath());

                final StructStat stat = Os.stat(mFile.getPath());

                synchronized (mLock) {

                synchronized (mLock) {

                    mStatTimestamp = stat.st_mtime;

                    mStatTimestamp = stat.st_mtim;

                    mStatSize = stat.st_size;

                    mStatSize = stat.st_size;

                }

                }

            } catch (ErrnoException e) {

            } catch (ErrnoException e) {