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  • Will this make the object thread-safe?

    - by sharptooth
    I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my COM object will ever try to simultaneously use the object from more than one thread. So I want the solution as simple as possible as long as it meets the requirement above. Here's what I came up with. I add a mutex or critical section as a member variable of the object. Every COM-exposed method will acquire the mutex/section at the beginning and release before returning control. I understand that this solution doesn't provide fine-grained access and this might slow execution down, but since I suppose simultaneous access will not really occur I don't care of this. Will this solution suffice? Is there a simpler solution?

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  • memcpy() safety on adjacent memory regions

    - by JaredC
    I recently asked a question on using volatile and was directed to read some very informative articles from Intel and others discussing memory barriers and their uses. After reading these articles I have become quite paranoid though. I have a 64-bit machine. Is it safe to memcpy into adjacent, non-overlapping regions of memory from multiple threads? For example, say I have a buffer: char buff[10]; Is it always safe for one thread to memcpy into the first 5 bytes while a second thread copies into the last 5 bytes? My gut reaction (and some simple tests) indicate that this is completely safe, but I have been unable to find documentation anywhere that can completely convince me.

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  • ThreadExceptionEventHandler and invoking delegates

    - by QmunkE
    If I assign a ThreadExceptionEventHandler to Application.ThreadException, why when I invoke a delegate method using a control on the main application thread are any exceptions thrown by that delegate not triggering the event handler? i.e. static void Main() { ... Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException); Application.Run(new Form1()); } static void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e) { Console.Error.Write("A thread exception occurred!"); } ... private void Form1_Load(object sender, EventArgs e) { Thread syncThread = new Thread(new ThreadStart(this.ThrowException)); syncThread.Start(); } private void ThrowException() { button1.Invoke(new MethodInvoker(delegate { // Not handled by ThreadExceptionEventHandler? throw new Exception(); })); } The context on this is that I have a background thread started from a form which is throwing an unhandled exception which terminates the application. I know this thread is going to be unreliable since it is network connectivity reliant and so subject to being terminated at any point, but I'm just interested as to why this scenario doesn't play out as I expect?

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  • How are the concepts of process and threads implementated in Linux kernel?

    - by Shan
    Can any one explain how are the concepts of process and threads implemented in Linux kernel ? I am looking for an intuitive explanation with some C snippets ( and important data structures) that clearly distinguishes between the two. I am just looking for the key implementation ideas I should get hold off. Essentially, I want to understand them and implement something similar in an embedded target (not supporte by any OS) in C language.

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  • What are common uses of condition variables in C++?

    - by jasonline
    I'm trying to learn about condition variables. I would like to know what are the common situations where condition variables are used. One example is in a blocking queue, where two threads access the queue - the producer thread pushes an item into the queue, while the consumer thread pops an item from the queue. If the queue is empty, the consumer thread is waiting until a signal is sent by the producer thread. What are other design situations where you need a condition variable to be used?

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  • What is wrong with my @synchronized block?

    - by hyn
    I have 2 threads in my application, a game update thread and render/IO/main thread. My update thread updates the game state, and the render thread renders the scene based on the updated values of the game state models and a few other variables stored inside an object (gameEngine). The render thread gets executed while the game thread is still updating, which is a problem, so it appeared to me the solution is to use @synchronized like this: @synchronized(gameEngine) { [gameEngine update]; nextUpdate = now + GAME_UPDATE_INTERVAL; gameEngine.lastGameUpdateInterval = now - lastUpdate; gameEngine.lastGameUpdateTime = now; lastUpdate = now; } But the render thread still accesses the gameEngine object between -update and the last 3 lines of the block. Why is this?

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  • What to use to wait on a indeterminate number of tasks?

    - by Scott Chamberlain
    I am still fairly new to parallel computing so I am not too sure which tool to use for the job. I have a System.Threading.Tasks.Task that needs to wait for n number number of tasks to finish before starting. The tricky part is some of its dependencies may start after this task starts (You are guaranteed to never hit 0 dependent tasks until they are all done). Here is kind of what is happening Parent thread creates somewhere between 1 and (NUMBER_OF_CPU_CORES - 1) tasks. Parent thread creates task to be run when all of the worker tasks are finished. Parent thread creates a monitoring thread Monitoring thread may kill a worker task or spawn a new task depending on load. I can figure out everything up to step 4. How do I get the task from step 2 to wait to run until any new worker threads created in step 4 finish?

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  • Best way to reuse a Runnable

    - by Gandalf
    I have a class that implements Runnable and am currently using an Executor as my thread pool to run tasks (indexing documents into Lucene). executor.execute(new LuceneDocIndexer(doc, writer)); My issue is that my Runnable class creates many Lucene Field objects and I would rather reuse them then create new ones every call. What's the best way to reuse these objects (Field objects are not thread safe so I cannot simple make them static) - should I create my own ThreadFactory? I notice that after a while the program starts to degrade drastically and the only thing I can think of is it's GC overhead. I am currently trying to profile the project to be sure this is even an issue - but for now lets just assume it is.

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  • Not Able to call The method Asynchronously in the Unit Test.

    - by user43838
    Hi everyone, I am trying to call a method that passes an object called parameters. public void LoadingDataLockFunctionalityTest() { DataCache_Accessor target = DataCacheTest.getNewDataCacheInstance(); target.itemsLoading.Add("WebFx.Caching.TestDataRetrieverFactorytestsync", true); DataParameters parameters = new DataParameters("WebFx.Core", "WebFx.Caching.TestDataRetrieverFactory", "testsync"); parameters.CachingStrategy = CachingStrategy.TimerDontWait; parameters.CacheDuration = 0; string data = (string)target.performGetForTimerDontWaitStrategy(parameters); TestSyncDataRetriever.SimulateLoadingForFiveSeconds = true; Thread t1 = new Thread(delegate() { string s = (string)target.performGetForTimerDontWaitStrategy(parameters); Console.WriteLine(s ?? String.Empty); }); t1.Start(); t1.Join(); Thread.Sleep(1000); ReaderWriterLockSlim rw = DataCache_Accessor.GetLoadingLock(parameters); Assert.IsTrue(rw.IsWriteLockHeld); Assert.IsNotNull(data); } My test is failing all the time and i am not able step through the method.. Can someone please put me in the right direction Thanks

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  • C++ Simple thread with parameter (no .net)

    - by Marc Vollmer
    I've searched the internet for a while now and found different solutions but then all don't really work or are to complicated for my use. I used C++ until 2 years ago so it might be a bit rusty :D I'm currently writing a program that posts data to an URL. It only posts the data nothing else. For posting the data I use curl, but it blocks the main thread and while the first post is still running there will be a second post that should start. In the end there are about 5-6 post operations running at the same time. Now I want to push the posting with curl into another thread. One thread per post. The thread should get a string parameter with the content what to push. I'm currently stuck on this. Tried the WINAPI for windows but that crashes on reading the parameter. (the second thread is still running in my example while the main thread ended (waiting on system("pause")). It would be nice to have a multi plattform solution, because it will run under windows and linux! Heres my current code: #define CURL_STATICLIB #include <curl/curl.h> #include <curl/easy.h> #include <cstdlib> #include <iostream> #include <stdio.h> #include <stdlib.h> #include <string> #if defined(WIN32) #include <windows.h> #else //#include <pthread.h> #endif using namespace std; void post(string post) { // Function to post it to url CURL *curl; // curl object CURLcode res; // CURLcode object curl = curl_easy_init(); // init curl if(curl) { // is curl init curl_easy_setopt(curl, CURLOPT_URL, "http://10.8.27.101/api.aspx"); // set url string data = "api=" + post; // concat post data strings curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str()); // post data res = curl_easy_perform(curl); // execute curl_easy_cleanup(curl); // cleanup } else { cerr << "Failed to create curl handle!\n"; } } #if defined(WIN32) DWORD WINAPI thread(LPVOID data) { // WINAPI Thread string pData = *((string*)data); // convert LPVOID to string [THIS FAILES] post(pData); // post it with curl } #else // Linux version #endif void startThread(string data) { // FUnction to start the thread string pData = data; // some Test #if defined(WIN32) CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)thread, &pData, 0, NULL); // Start a Windows thread with winapi #else // Linux version #endif } int main(int argc, char *argv[]) { // The post data to send string postData = "test1234567890"; startThread(postData); // Start the thread system("PAUSE"); // Dont close the console window return EXIT_SUCCESS; } Has anyone a suggestion? Thanks for the help!

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  • Lua operations, that works in mutitheaded environment

    - by SBKarr
    My application uses Lua in multithreaded environment with global mutex. It implemented like this: Thread locks mutex, Call lua_newthread Perform some initialization on coroutine Run lua_resume on coroutine Unlocks mutex lua_lock/unlock is not implemented, GC is stopped, when lua works with coroutine. My question is, can I perform steps 2 and 3 without locking, if initialisation process does not requires any global Lua structs? Can i perform all this process without locking at all, if coroutine does not requires globals too? In what case I generally can use Lua functions without locking?

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  • How to terminate a managed thread blocked in unmanaged code?

    - by James Curran
    I have a managed thread which is waiting, blocked, in an unmanaged code (specifically, it on a call to NamedPipeServerStream.WaitForConnection() which ultimitely calls into unmanaged code, and does not offer a timeout). I want to shut the thread down neatly. Thread.Abort() has no effect until the code returns to the managed realm, which it won't do until a client makes a connection, which we can't wait for). I need a way "shock" it out of the unmanaged code; or a way to just kill the thread even while it's in unmanaged land.

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  • DataGridView cells not editable when using an outside thread call

    - by joslinm
    Hi, I'm not able to edit my datagridview cells when a number of identical calls takes place on another thread. Here's the situation: Dataset table is created in the main window The program receives in files and processes them on a background thread in class TorrentBuilder : BackgroundWorker creating an array objects of another class Torrent My program receives those objects from the BW result and adds them into the dataset The above happens either on my main window thread or in another thread: I have a separate thread watching a folder for files to come in, and when they do come in, they proceed to call TorrentBuilder.RunWorkerAsynch() from that thread, receive the result, and call an outside class that adds the Torrent objects into the table. When the files are received by the latter thread, the datagridview isn't editable. All of the values come up properly into the datagridview, but when I click on a cell to edit it: I can write letters and everything, but when I click out of it, it immediately reverts back to its original value. If I restart the program, I can edit the same cells just fine. If the values are freshly added from the main window thread, I can edit the cells just fine. The outside thread is called from my main window thread, and sits there in the background. I don't believe it to be ReadOnly because I would have gotten an exception. Here's some code: From my main window class: private void dataGridView_DragDrop(object sender, DragEventArgs e) { ArrayList al = new ArrayList(); string[] files = (string[])e.Data.GetData(DataFormats.FileDrop); foreach (string file in files) { string extension = Path.GetExtension(file); if (Path.GetExtension(file).Equals(".zip") || Path.GetExtension(file).Equals(".rar")) { foreach (string unzipped in dh.UnzipFile(file)) al.Add(unzipped); } else if (Path.GetExtension(file).Equals(".torrent")) { al.Add(file); } } dataGridViewProgressBar.Visible = true; tb.RunWorkerCompleted += new RunWorkerCompletedEventHandler(tb_DragDropCompleted); tb.ProgressChanged += new ProgressChangedEventHandler(tb_DragDropProgress); tb.RunWorkerAsync() } void tb_DragDropCompleted(object sender, RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(data); dataGridViewProgressBar.Visible = false; } From my outside Thread while (autocheck) { if (torrentFiles != null) { builder.RunWorkerAsync(torrentFiles); while (builder.IsBusy) Thread.Sleep(500); } } void builder_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(xml); data.Save(); //Save just does an `AcceptChanges()` and saves to a XML file }

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  • How to keep a .NET console app running?

    - by intoorbit
    Consider a Console application that starts up some services in a separate thread. All it needs to do is wait for the user to press Ctrl+C to shut it down. Which of the following is the better way to do this? static ManualResetEvent _quitEvent = new ManualResetEvent(false); static void Main() { Console.CancelKeyPress += delegate { _quitEvent.Set(); }; // kick off asynchronous stuff _quitEvent.WaitOne(); // cleanup/shutdown and quit } Or this, using Thread.Sleep(1): static bool _quitFlag = false; static void Main() { Console.CancelKeyPress += delegate { _quitFlag = true; }; // kick off asynchronous stuff while (!_quitFlag) { Thread.Sleep(1); } // cleanup/shutdown and quit }

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  • Thread-safe use of a singleton's members

    - by Anthony Mastrean
    I have a C# singleton class that multiple classes use. Is access through Instance to the Toggle() method thread-safe? If yes, by what assumptions, rules, etc. If no, why and how can I fix it? public class MyClass { private static readonly MyClass instance = new MyClass(); public static MyClass Instance { get { return instance; } } private int value = 0; public int Toggle() { if(value == 0) { value = 1; } else if(value == 1) { value = 0; } return value; } }

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  • How to get a stable, snappy UI using threads?

    - by Thomas Ahle
    I recently watching this video on Google Chrome with great interest. It explains that Google Chrome uses one thread for IO, one for opening files and one for intermodule communication. I think I may be able to use something similar for my own - currently quite messy - application. I wondered if there were any good articles on best-practices or patterns for such threaded divisions of tasks?

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  • Is my way of doing threads in Android correct?

    - by Charlie
    Hi, I'm writing a live wallpaper, and I'm forking off two separate threads in my main wallpaper service. One updates, and the other draws. I was under the impression that once you call thread.start(), it took care of everything for you, but after some trial and error, it seems that if I want my update and draw threads to keep running, I have to manually keep calling their run() methods? In other words, instead of calling start() on both threads and forgetting, I have to manually set up a delayed handler event that calls thread.run() on both the update and draw threads every 16 milliseconds. Is this the correct way of having a long running thread? Also, to kill threads, I'm just setting them to be daemons, then nulling them out. Is this method ok? Most examples I see use some sort of join() / interrupt() in a while loop...I don't understand that one...

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  • SQL Server stored procedure in multi threaded environments

    - by Shamika
    Hi, I need to execute some Sql server stored procs in a thread safe manner. At the moment I'm using software locks (C# locks) to achieve this but wonder what kind of features provided by the Sql server itself to achieve thread safety. It seems to be there are some table and row locking features built in to Sql server. Also from a performance perspective what is best approach? Software locks? Or Sql Server built in locks? Thanks, Shamika

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  • Why onCreate() calling multiple times when i use Thread()?

    - by RajaReddy PolamReddy
    In my app i faced a problem with threads. i am using native code in my app. i try to load library and then calling native functions from the android code. 1. By using Threads() : PjsuaThread pjsuaThread = new PjsuaThread(); pjsuaThread.start(); thread code class PjsuaThread extends Thread { public void run() { if (pjsua_app.initApp() != 0) { // native function calling return; } else { } pjsua_app.startPjsua(ApjsuaActivity.CFG_FNAME); // native function calling finished = true; } When i use code like this, onCreate() function calling multiple times and able to load library and calling some functions properly, after some seconds onCreate calling again because of that it's crashing. 2. Using AsyncTask(): And also i used AsyncTask< for this requirement, it's crashing the application( crashing in lib code ). not able to open any functions class SipTask extends AsyncTask<Void, String, Void> { protected Void doInBackground(Void... args) { if (pjsua_app.initApp() != 0) { return null; } else { } pjsua_app.startPjsua(ApjsuaActivity.CFG_FNAME); finished = true; return null; } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); Log.i(TAG, "On POst "); } } What is annoying is that in most cases it is not the missing library, it's tried to able to load the lib crashing in between. any one know the reason ?

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  • How solve consumer/producer task using semaphores

    - by user1074896
    I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct). public class SimpleProducerConsumer { private Stack<Object> stack = new Stack<Object>(); private static final int STACK_MAX_SIZE = 10; public static void main(String[] args) { SimpleProducerConsumer pc = new SimpleProducerConsumer(); new Thread(pc.new Producer(), "p1").start(); new Thread(pc.new Producer(), "p2").start(); new Thread(pc.new Consumer(), "c1").start(); new Thread(pc.new Consumer(), "c2").start(); new Thread(pc.new Consumer(), "c3").start(); } public synchronized void push(Object d) { while (stack.size() >= STACK_MAX_SIZE) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } stack.push(new Object()); System.out.println("push " + Thread.currentThread().getName() + " " + stack.size()); notify(); } public synchronized Object pop() { while (stack.size() == 0) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } stack.pop(); System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size()); notify(); return null; } class Consumer implements Runnable { @Override public void run() { while (true) { pop(); } } } class Producer implements Runnable { @Override public void run() { while (true) { push(new Object()); } } } } I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package) How I need to change code to exchange java objects monitors to my custom semaphore. (To illustrate C/P problem using semaphores) Semaphore: class Semaphore { private int counter; public Semaphore() { this(0); } public Semaphore(int i) { if (i < 0) throw new IllegalArgumentException(i + " < 0"); counter = i; } public synchronized void release() { if (counter == 0) { notify(); } counter++; } public synchronized void acquire() throws InterruptedException { while (counter == 0) { wait(); } counter--; } }

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  • executorservice to read data from database in chuncks and run process on them

    - by TazMan
    I'm trying to write a process that would read data from a database and upload it onto a cloud datastore. How can I decide the partition strategy of the data? I want to query the table in chunks and process each chunk in 10 threads. Each thread basically will send the data to an individual node on a 10 node cluster on the cloud.. Where in the below multi threading code will the dataquery to extract and send 10 concurrent requests for uploading data to cloud would be? public class Caller { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < 10; i++) { Runnable worker = new DomainCDCProcessor(i); executor.execute(worker); } executor.shutdown(); while (!executor.isTerminated()) { } System.out.println("Finished all threads"); } }

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  • how to run TimerTask off main UI thread?

    - by huskyd97
    I am having trouble with a TimerTask Interfering with In App Purchasing (Async Tasks). I am weak with Threads, so I believe it is running on the main UI thread, eating up resources. How can I run this outside the UI thread? I have searched, and tried some suggestions using handlers. but seems like I get the same result, app gets really laggy. when I don't run this task (refreshes every 500mS), the activity runs smoothly, and there are no hangs during In app purchases. Your help is appreciated, code snippet below: public class DummyButtonClickerActivity extends Activity { protected Timer timeTicker = new Timer("Ticker"); private Handler timerHandler = new Handler(); protected int timeTickDown = 20; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.mainhd); // start money earned timer handler TimerTask tick = new TimerTask() { public void run() { myTickTask(); } }; timeTicker.scheduleAtFixedRate(tick, 0, 500); // 500 ms each } // End OnCreate protected void myTickTask() { if (timeTickDown == 0) { /// run my code here //total = total + _Rate; timerHandler.post(doUpdateTimeout); } else if(timeTickDown < 0) { // do nothing } timeTickDown--; } private Runnable doUpdateTimeout = new Runnable() { public void run() { updateTimeout(); } }; private void updateTimeout() { // reset tick timeTickDown = 2; // 2* 500ms == once a second } }

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  • Threads in PHP.

    - by Muhammad Sajid
    Hello.. I am creating a web application using zend, here i create an interface from where user-A can send email to more than one user(s) & it works excellent but it slow the execution time because of which user-A wait too much for the "acknowledged response" ( which will show after the emails have sent. ) In Java there are "Threads" by which we can perform that task (send emails) & it does not slow the rest application. Is there any technique in PHP/Zend just like in Java by which we can divide our tasks which could take much time eg: sending emails. Thanks..

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