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I have android app that talks to server and syncs some data int SQLite database. There is service that runs every 5 minutes and spans AsyncTask that grabs data and insert/update data into database.

Here is my issue. When background process updates database it might take some considerable time. If user trying to use application at the same time and opens ListView with cursor bound to that same table - I get deadlock situation and ANR report.

How should I solve this problem properly?

I FEEL like I need to check from UI if asyncprocess running (how?) and if yes then show user that background refresh going on and load list as soon as process accessing data finished on background.

What is proper way to solve this issue?

EDIT

Here is report

DALVIK THREADS:
"main" prio=5 tid=1 WAIT
  | group="main" sCount=1 dsCount=0 s=N obj=0x2aac88b8 self=0xcd58
  | sysTid=3967 nice=0 sched=0/0 cgrp=unknown handle=1876207664
  at java.lang.Object.wait(Native Method)
  - waiting on <0x2aac8948> (a java.lang.VMThread)
  at java.lang.Thread.parkFor(Thread.java:1535)
  at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48)
  at sun.misc.Unsafe.park(Unsafe.java:317)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:131)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:790)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:823)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1153)
  at java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:200)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:261)
  at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:375)
  at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:61)
  at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:283)
  at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:264)
  at android.content.ContentResolver.query(ContentResolver.java:251)
  ****************at com.idatt.data.PreferenceData.getPreferenceString(PreferenceData.java:119)
  at com.idatt.data.PreferenceData.getPreferenceBoolean(PreferenceData.java:109)
  at com.idatt.common.Preferences.getIsShowRates(Preferences.java:136)
  at com.idatt.activities.TripListActivity$TripViewDataHolder.populateFrom(TripListActivity.java:211)
  at com.idatt.activities.TripListActivity$TripListCursorAdapter.getView(TripListActivity.java:147)
  at android.widget.AbsListView.obtainView(AbsListView.java:1294)
  at android.widget.ListView.measureHeightOfChildren(ListView.java:1198)
  at android.widget.ListView.onMeasure(ListView.java:1109)
  at android.view.View.measure(View.java:8187)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3146)
  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
  at android.view.View.measure(View.java:8187)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3146)
  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
  at android.view.View.measure(View.java:8187)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3146)
  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
  at android.view.View.measure(View.java:8187)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3146)
  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
  at android.view.View.measure(View.java:8187)
  at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
  at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
  at android.os.Handler.dispatchMessage(Handler.java:99)
  at android.os.Looper.loop(Looper.java:123)
  at android.app.ActivityThread.main(ActivityThread.java:4644)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:521)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
  at dalvik.system.NativeStart.main(Native Method)

"Binder Thread #3" prio=5 tid=14 NATIVE
  | group="main" sCount=1 dsCount=0 s=N obj=0x3033f218 self=0x2394d0
  | sysTid=4305 nice=0 sched=0/0 cgrp=unknown handle=2332488
  at dalvik.system.NativeStart.run(Native Method)

"AsyncTask #5" prio=5 tid=13 WAIT
  | group="main" sCount=1 dsCount=0 s=N obj=0x300dc038 self=0x25f0e0
  | sysTid=4073 nice=10 sched=0/0 cgrp=unknown handle=2965040
  at java.lang.Object.wait(Native Method)
  - waiting on <0x3013c610> (a java.lang.VMThread)
  at java.lang.Thread.parkFor(Thread.java:1535)
  at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48)
  at sun.misc.Unsafe.park(Unsafe.java:317)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:131)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:790)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:823)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1153)
  at java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:200)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:261)
  at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:375)
  at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1533)
  at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1410)
  at com.idatt.data.Provider.insert(Provider.java:198)
  at android.content.ContentProvider$Transport.insert(ContentProvider.java:174)
  at android.content.ContentResolver.insert(ContentResolver.java:587)
  *************at com.idatt.data.TripData.InsertTrip(TripData.java:272)
  at com.idatt.common.AsyncProcessor.GetUserTrips(AsyncProcessor.java:252)
  at com.idatt.common.AsyncProcessor.doInBackground(AsyncProcessor.java:101)
  at com.idatt.common.AsyncProcessor.doInBackground(AsyncProcessor.java:27)
  at android.os.AsyncTask$2.call(AsyncTask.java:185)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
  at java.lang.Thread.run(Thread.java:1096)

"AsyncTask #4" prio=5 tid=12 WAIT
  | group="main" sCount=1 dsCount=0 s=N obj=0x302ffd28 self=0x4e8f30
  | sysTid=4072 nice=10 sched=0/0 cgrp=unknown handle=5163584
  at java.lang.Object.wait(Native Method)
  - waiting on <0x302ffbd8> (a java.lang.VMThread)
  at java.lang.Thread.parkFor(Thread.java:1535)
  at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48)
  at sun.misc.Unsafe.park(Unsafe.java:317)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:131)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:790)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:823)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1153)
  at java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:200)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:261)
  at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:375)
  at android.database.sqlite.SQLiteProgram.close(SQLiteProgram.java:291)
  at android.database.sqlite.SQLiteQuery.close(SQLiteQuery.java:133)
  at android.database.sqlite.SQLiteCursor.close(SQLiteCursor.java:502)
  at android.database.CursorWrapper.close(CursorWrapper.java:45)
  at android.content.ContentResolver$CursorWrapperInner.close(ContentResolver.java:1355)
  ************at com.idatt.data.LogData.getLogItems(LogData.java:118)
  at com.idatt.data.LogData.getLogItems(LogData.java:125)
  at com.idatt.common.AsyncProcessor.PostDeviceLogs(AsyncProcessor.java:210)
  at com.idatt.common.AsyncProcessor.doInBackground(AsyncProcessor.java:96)
  at com.idatt.common.AsyncProcessor.doInBackground(AsyncProcessor.java:27)
  at android.os.AsyncTask$2.call(AsyncTask.java:185)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
  at java.lang.Thread.run(Thread.java:1096)

"AsyncTask #3" prio=5 tid=11 WAIT
  | group="main" sCount=1 dsCount=0 s=N obj=0x302ec858 self=0x4ff440
  | sysTid=4071 nice=10 sched=0/0 cgrp=unknown handle=2984848
  at java.lang.Object.wait(Native Method)
  - waiting on <0x302ec9b0> (a java.lang.VMThread)
  at java.lang.Thread.parkFor(Thread.java:1535)
  at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48)
  at sun.misc.Unsafe.park(Unsafe.java:317)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:131)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1996)
  at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:359)
  at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1001)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1061)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
  at java.lang.Thread.run(Thread.java:1096)

"AsyncTask #2" prio=5 tid=10 WAIT
  | group="main" sCount=1 dsCount=0 s=N obj=0x302c31a8 self=0x4dca78
  | sysTid=4062 nice=10 sched=0/0 cgrp=unknown handle=5111608
  at java.lang.Object.wait(Native Method)
  - waiting on <0x3027ab38> (a java.lang.VMThread)
  at java.lang.Thread.parkFor(Thread.java:1535)
  at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48)
  at sun.misc.Unsafe.park(Unsafe.java:317)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:131)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:790)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:823)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1153)
  at java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:200)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:261)
  at android.database.sqlite.SQLiteDatabase....

See trace attached. Check lines that I marked with ** I'm not great at reading it but here is my conclusions.. Seems like it is blocking when trying to execute

com.idatt.data.PreferenceData.getPreferenceString

This call opens DB in read-only mode (it's going through my COntentProvider). And this call happens on UI thread.

What's bad - I noticed 2 other calls: InsertTrips and getLogData. InsertTrips goes into database but getLogData should be read-only as well. However, they both part of same AsyncTask. So, it seems like one instance of AsyncTask was originated from Service/Alarm (every 5 minutes deal) and second instance was originated by user (I give them option to manually refresh).

Situation look like this:

  • App updates itself on schedule
  • User uses app and calls refresh manually
  • After user initiated manual refresh - she tries to use app where it's accessing same data..
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2 Answers 2

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1

Does it lock as you use the table that is used to get a cursor for the list or does it lock because you access the database. If lock is table based, ou could consider having two tables, on for the service and one for the view, or two tables and you switch to one for display and use the other one for filling data...

If lock is database based and not table based, another solution that comes to my mind is that you could cache the data from database when you get it for the table, use an arrayadapter instead of the cursor adapter. Query your database, fill the cache and display it so that database can be used by the service filling it with new values. After the service terminates, you could send a oberserupdate to notify the UI to pick up new data and refill its cache.

Regards, Stéphane

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1 Comment

See more details that I posted
0

If you are using AsyncTask properly, it shouldn't block your UI thread. Without code, it is hard to say what is going wrong here. A few things to check:

  • Make sure you all calling AsyncTask.execute() and now AsyncTask.doInBackground(). Calling doInBackground() directly will run that code on the UI thread.

  • Are you manually synchronizing on some object that is locked during the update?

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3 Comments

Yes to all. I call it properly - but blocking is on DB, not on AsyncTask
Thanks for adding more information. Also noticed that you have a few AsyncTasks running at the same time. Unless you are using HoneyComb, AsyncTasks execute in parallel. Just another thing to watch for.
I just added more comments on bottom after trace. User that reports it runs 2.2. I support back to 2.1 and my own device of course 2.3.4 :) Yes, it's possible for same AsyncTask to run in parallel. What should I do to eliminate that?

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