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  • Sync between local service with a thread and an activity

    - by Henrik
    Hello all, I'm trying to think of a way on how to sync in between a local service and the main activity. The local service has, A thread with a socket connection that could receive data at any time. A list/array with data. At any time the socket could receive data and add it to the list. The activity needs to display this data. So when the activity starts up it needs to attach or start the local service and fetch the list. It also needs to be notified if the list is updated. I think I would need to sync my list somehow so the local service does not add a new entry to it while the activity fetches the list when connecting to the service. Any ideas? Thanks.

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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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  • Activate thread synchronically

    - by mayap
    Hi All, I'm using .Net 4.0 parallel library. The tasks I execute, ask to run some other task, sometimes synchronically and somethimes asynchronically, dependending on some conditions which are not known in advanced. For async call, i simply create new tasks and that's it. I don't know how to handly sync call: how to run it from the same thread, maybe that sync tasks will also ask to execute sync tasks recursively. all this issue is pretty new to me. thanks in advance.

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  • Thread Suicide on Shutdown?

    - by yar
    I have a java.util.Timer running at a fixed interval. I have added a Runtime#addShutdownHook and it shuts down when the VM ends normally or abnormally. However, it keeps the VM alive when a main terminates, unless I insist by doing a System.exit in the main. Is there any way for me to check if I'm the last Thread standing, or some other way to avoid altering a main that would exit normally on finish? Note: I know a lot of people believe that java.util.Timer is deprecated (it's not), but unless your alternative helps me solve this problem...

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  • Is MSDN referencing a system.thread, a worker thread, an io thread or all three?

    - by w0051977
    Please see the warning below taken from the StreamWriter class specification (http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx): "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." I understand that a W3WC process contains two thread pools i.e. worker threads and I/O threads. A worker thread could contain many threads of its own (if the application creates its own System.Thread instances). Does the warning only relate to System.Threads or does it relate to worker threads and I/O threads as well I.e. as the instance variables of the streamwriter class are not thread safe then does this mean that there would be problems if multiple worker threads access it eg if two users on two different web clients attempt to write to the log file at the same time, then could one lock out the other?

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  • Thread Synchronization and Synchronization Primitives

    When considering synchronization in an application, the decision truly depends on what the application and its worker threads are going to do. I would use synchronization if two or more threads could possibly manipulate the same instance of an object at the same time. An example of this in C# can be demonstrated through the use of storing data in a static object. A static object is initialized once per application and the data within the object can be accessed by all threads. I would use the synchronization primitives to prevent any data from being manipulated by multiple threads simultaneously. This would reduce any data corruption from occurring within the object. On the other hand if all the threads used non static objects and were independent of the other tasks there would be no need to use synchronization. Synchronization Primitives in C#: Basic Blocking Locking Signaling Non-Blocking Synchronization Constructs The Basic Blocking methods include Sleep, Join, and Task.Wait.  These methods force threads to wait until other threads have completed. In addition, these methods can also force a thread to wait a set amount of time before continuing to work.   The Locking primitive prevents a thread from entering a critical section of code while another thread is in the same critical section.  If another thread attempts to enter a locked code, it will wait, until the code block is released. The Signaling primitive allows a thread to temporarily pause work until receiving a notification from another thread that it is ok to continue working. The Signaling primitive removes the need for polling.The Non-Blocking Synchronization Constructs protect access to a common field by calling upon processor primitives.

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  • Boost::thread mutex issue: Try to lock, access violation

    - by user1419305
    I am currently learning how to multithread with c++, and for that im using boost::thread. I'm using it for a simple gameengine, running three threads. Two of the threads are reading and writing to the same variables, which are stored inside something i call PrimitiveObjects, basicly balls, plates, boxes etc. But i cant really get it to work, i think the problem is that the two threads are trying to access the same memorylocation at the same time, i have tried to avoid this using mutex locks, but for now im having no luck, this works some times, but if i spam it, i end up with this exception: First-chance exception at 0x00cbfef9 in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. Unhandled exception at 0x77d315de in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. These are the functions inside the object that im using for this, and the debugger is also blaming them for the exception. void PrimitiveObj::setPos(glm::vec3 in){ boost::mutex mDisposingMutex; boost::try_mutex::scoped_try_lock lock(mDisposingMutex); if ( lock) { position = in; boost::try_mutex::scoped_try_lock unlock(mDisposingMutex); } } glm::vec3 PrimitiveObj::getPos(){ boost::mutex myMutex; boost::try_mutex::scoped_try_lock lock(myMutex); if ( lock) { glm::vec3 curPos = position; boost::try_mutex::scoped_try_lock unlock(myMutex); return curPos; } return glm::vec3(0,0,0); } Any ideas?

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  • MMGR Questions, code use and thread-saftey

    - by chadb
    1) Is MMGR thread safe? 2) I was hoping someone could help me understand some code. I am looking at something where a macro is used, but I don't understand the macro. I know it contains a function call and an if check, however, the function is a void function. How does wrapping "(m_setOwner (FILE,_LINE_,FUNCTION),false)" ever change return types? #define someMacro (m_setOwner(__FILE__,__LINE__,__FUNCTION__),false) ? NULL : new ... void m_setOwner(const char *file, const unsigned int line, const char *func); 3) What is the point of the reservoir? 4) On line 770 ("void *operator new(size_t reportedSize)" there is the line "// ANSI says: allocation requests of 0 bytes will still return a valid value" Who/what is ANSI in this context? Do they mean the standards? 5) This is more of C++ standards, but where does "reportedSize" come from for "void *operator new(size_t reportedSize)"? 6) Is this the code that is actually doing the allocation needed? "au-actualAddress = malloc(au-actualSize);"

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  • Is it safe to use a boolean flag to stop a thread from running in C#

    - by Lirik
    My main concern is with the boolean flag... is it safe to use it without any synchronization? I've read in several places that it's atomic. class MyTask { private ManualResetEvent startSignal; private CountDownLatch latch; private bool running; MyTask(CountDownLatch latch) { running = false; this.latch = latch; startSignal = new ManualResetEvent(false); } // A method which runs in a thread public void Run() { startSignal.WaitOne(); while(running) { startSignal.WaitOne(); //... some code } latch.Signal(); } public void Stop() { running = false; startSignal.Set(); } public void Start() { running = true; startSignal.Set(); } public void Pause() { startSignal.Reset(); } public void Resume() { startSignal.Set(); } } Is this a safe way to design a task? Any suggestions, improvements, comments? Note: I wrote my custom CountDownLatch class in case you're wondering where I'm getting it from.

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  • Is there a straightforward way to have a thread-local instance variable?

    - by Dan Tao
    With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there any straightforward way to declare a class member as thread-local, meaning, each class instance gets an object per thread?

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  • Synchronizing issue: I want the main thread to be run before another thread but it sometimes doesn´t

    - by Rox
    I have done my own small concurrency framework (just for learning purposes) inspired by the java.util.concurrency package. This is about the Callable/Future mechanism. My code below is the whole one and is compilable and very easy to understand. My problem is that sometimes I run into a deadlock where the first thread (the main thread) awaits for a signal from the other thread. But then the other thread has already notified the main thread before the main thread went into waiting state, so the main thread cannot wake up. FutureTask.get() should always be run before FutureTask.run() but sometimes the run() method (which is called by new thread) runs before the get() method (which is called by main thread). I don´t know how I can prevent that. This is a pseudo code of how I want the two threads to be run. //From main thread: Executor.submit().get() (in get() the main thread waits for new thread to notify) ->submit() calls Executor.execute(FutureTask object) -> execute() starts new thread -> new thread shall notify `main thread` I cannot understand how the new thread can start up and run faster than the main thread that actually starts the new thread. Main.java: public class Main { public static void main(String[] args) { new ExecutorServiceExample(); } public Main() { ThreadExecutor executor = new ThreadExecutor(); Integer i = executor.submit(new Callable<Integer>() { @Override public Integer call() { return 10; } }).get(); System.err.println("Value: "+i); } } ThreadExecutor.java: public class ThreadExecutor { public ThreadExecutor() {} protected <V> RunnableFuture<V> newTaskFor(Callable c) { return new FutureTask<V>(c); } public <V> Future<V> submit(Callable<V> task) { if (task == null) throw new NullPointerException(); RunnableFuture<V> ftask = newTaskFor(task); execute(ftask); return ftask; } public void execute(Runnable r) { new Thread(r).start(); } } FutureTask.java: import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.ReentrantLock; import java.util.logging.Level; import java.util.logging.Logger; public class FutureTask<V> implements RunnableFuture<V> { private Callable<V> callable; private volatile V result; private ReentrantLock lock = new ReentrantLock(); private Condition condition = lock.newCondition(); public FutureTask(Callable callable) { if (callable == null) throw new NullPointerException(); this.callable = callable; } @Override public void run() { acquireLock(); System.err.println("RUN"+Thread.currentThread().getName()); V v = this.callable.call(); set(v); condition.signal(); releaseLock(); } @Override public V get() { acquireLock(); System.err.println("GET "+Thread.currentThread().getName()); try { condition.await(); } catch (InterruptedException ex) { Logger.getLogger(FutureTask.class.getName()).log(Level.SEVERE, null, ex); } releaseLock(); return this.result; } public void set(V v) { this.result = v; } private void acquireLock() { lock.lock(); } private void releaseLock() { lock.unlock(); } } And the interfaces: public interface RunnableFuture<V> extends Runnable, Future<V> { @Override void run(); } public interface Future<V> { V get(); } public interface Callable<V> { V call(); }

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  • Have main thread wait for a boost thread complete a task (but not finish).

    - by JAKE6459
    I have found plenty on making one thread wait for another to finish executing before continuing, but that is not what I wanted to do. I am not very familiar with using any multi-threading apis but right now I'm trying to learn boost. My situation is that I am using my main thread (the starting one from int main()) to create an instance of a class that is in charge of interacting with the main GUI. A class function is then called that creates a boost thread which in turn creates the GUI and runs the message pump. The thing I want to do is when my main thread calls the classes member function to create the GUI, I don't want that function to return until I tell it to from the newly created thread. This way my main thread can't continue and call more functions from the GUI class that interact with the GUI thread until that thread has completed GUI creation and entered the message loop. I think I may be able to figure it out if it was multiple boost thread objects interacting with each other, but when it is the main thread (non-boost object) interacting with a boost thread object, I get lost. Eventually I want a loop in my main thread to call a class function (among other tasks) to check if the user as entered any new input into the GUI (buy any changes detected by the message loop being updated into a struct and changing a bool to tell the main thread in the class function a change has occurred). Any suggestions for any of this would be greatly appreciated. This is the member function called by the main thread. int ANNGUI::CreateGUI() { GUIMain = new Main(); GUIThread = new boost::thread(boost::bind(&Main::MainThreadFunc, GUIMain)); return 0; }; This is the boost thread starting function. void Main::MainThreadFunc() { ANNVariables = new GUIVariables; WndProc = new WindowProcedure; ANNWindowsClass = new WindowsClass(ANNVariables, WndProc); ANNWindow = new MainWindow(ANNVariables); GUIMessagePump = new MessagePump; ANNWindow-ShowWindows(); while(true) { GUIMessagePump-ProcessMessage(); } }; BTW, everything compiles fine and when I run it, it works I just put a sleep() in the main thread so I can play with the GUI a little.

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  • Identity.Name is disposed in a IIS7 Asp.NET MVC application Thread

    - by vIceBerg
    I have made the smallest demo project to illustrate my problem. You can download the sources Here Visual Studio 2008, .NET 3.5, IIS7, Windows 7 Ultimate 32 bits. The IIS Website is configured ONLY for Windows Authentication in an Integreated pipeline app pool (DefaultAppPool). Here's the problem. I have an Asp.NET MVC 2 application. In an action, I start a thread. The View returns. The thread is doing it's job... but it needs to access Thread.CurrentPrincipal.Identity.Name BANG The worker process of IIS7 stops. I have a window that says: "Visual Studio Just-In-Time Debugger An unhandled exception ('System.Object.DisposedException') occured in w3wp.exe [5524]" I checked with the debugger and the Thread.CurrentPrincipal.Identity is valid, but the Name property is disposed. If I put a long wait in the action before it returns the view, then the Thread can do it's job and the Identity.Name is not disposed. So I think the Name gets disposed when the view is returned. For the sake of the discussion, here's the code that the thread runs (but you can also download the demo project. The link is on top of this post): private void Run() { const int SECTOWAIT = 3; //wait SECTOWAIT seconds long end = DateTime.Now.Ticks + (TimeSpan.TicksPerSecond * SECTOWAIT); while (DateTime.Now.Ticks <= end) continue; //Check the currentprincipal. BANG!!!!!!!!!!!!! var userName = Thread.CurrentPrincipal.Identity.Name; } Here's the code that starts the thread public void Start() { Thread thread = new Thread(new ParameterizedThreadStart(ThreadProc)); thread.SetApartmentState(ApartmentState.MTA); thread.Name = "TestThread"; thread.Start(this); } static void ThreadProc(object o) { try { Builder builder = (Builder)o; builder.Run(); } catch (Exception ex) { throw; } } So... what am i doing wrong? Thanks

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  • Pass a Message From Thread to Update UI

    - by Jay Dee
    Ive created a new thread for a file browser. The thread reads the contents of a directory. What I want to do is update the UI thread to draw a graphical representation of the files and folders. I know I can't update the UI from within a new thread so what I want to do is: whilst the file scanning thread iterates through a directories files and folders pass a file path string back to the UI thread. The handler in the UI thread then draws the graphical representation of the file passed back. public class New_Project extends Activity implements Runnable { private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { Log.d("New Thread","Proccess Complete."); Intent intent = new Intent(); setResult(RESULT_OK, intent); finish(); } }; public void getFiles(){ //if (!XMLEFunctions.canReadExternal(this)) return; pd = ProgressDialog.show(this, "Reading Directory.", "Please Wait...", true, false); Log.d("New Thread","Called"); Thread thread = new Thread(this); thread.start(); } public void run() { Log.d("New Thread","Reading Files"); getFiles(); handler.sendEmptyMessage(0); } public void getFiles() { for (int i=0;i<=allFiles.length-1;i++){ //I WANT TO PASS THE FILE PATH BACK TU A HANDLER IN THE UI //SO IT CAN BE DRAWN. **passFilePathBackToBeDrawn(allFiles[i].toString());** } } }

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  • Is this (Lock-Free) Queue Implementation Thread-Safe?

    - by Hosam Aly
    I am trying to create a lock-free queue implementation in Java, mainly for personal learning. The queue should be a general one, allowing any number of readers and/or writers concurrently. Would you please review it, and suggest any improvements/issues you find? Thank you. import java.util.concurrent.atomic.AtomicReference; public class LockFreeQueue<T> { private static class Node<E> { E value; volatile Node<E> next; Node(E value) { this.value = value; } } private AtomicReference<Node<T>> head, tail; public LockFreeQueue() { // have both head and tail point to a dummy node Node<T> dummyNode = new Node<T>(null); head = new AtomicReference<Node<T>>(dummyNode); tail = new AtomicReference<Node<T>>(dummyNode); } /** * Puts an object at the end of the queue. */ public void putObject(T value) { Node<T> newNode = new Node<T>(value); Node<T> prevTailNode = tail.getAndSet(newNode); prevTailNode.next = newNode; } /** * Gets an object from the beginning of the queue. The object is removed * from the queue. If there are no objects in the queue, returns null. */ public T getObject() { Node<T> headNode, valueNode; // move head node to the next node using atomic semantics // as long as next node is not null do { headNode = head.get(); valueNode = headNode.next; // try until the whole loop executes pseudo-atomically // (i.e. unaffected by modifications done by other threads) } while (valueNode != null && !head.compareAndSet(headNode, valueNode)); T value = (valueNode != null ? valueNode.value : null); // release the value pointed to by head, keeping the head node dummy if (valueNode != null) valueNode.value = null; return value; }

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  • java share data between thread

    - by ayush
    i have a java process that reads data from a socket server. Thus i have a BufferedReader and a PrintWriter object corresponding to that socket. Now in the same java process i have a multithreaded java server that accepts client connections. I want to achieve a functionality where all these clients that i accept can read data from the BufferedReader object that i mentioned above.(so that they can multiplex the data) How do i make these individual client threads read the data from BuffereReader single object? Sorry for the confusion.

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  • thread local stroage macosx

    - by anon
    http://developer.apple.com/mac/library/documentation/DeveloperTools/gcc-4.0.1/gcc/Thread_002dLocal.html Documents __thread yet my g++ compalins that __thread is not suppoted on my arch (Leopard on Macbookpro). Why is this? And how do I get around it?

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  • Cache consistency & spawning a thread

    - by Dave Keck
    Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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  • Is this ruby code thread safe?

    - by Ben K.
    Is this code threadsafe? It seems like it should be, because @myvar will never be assigned from multiple threads (assuming block completes in < 1s). But do I need to be worried about a situation where the second block is trying to read @myvar as it's being written? require 'rubygems' require 'eventmachine' @myvar = Time.now.to_i EventMachine.run do EventMachine.add_periodic_timer(1) do EventMachine.defer do @myvar = Time.now.to_i # some calculation and reassign end end EventMachine.add_periodic_timer(0.5) do puts @myvar end end

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  • How do I make a background thread in Java that allows the main application to exit completely? This

    - by Bob
    I have a Java application that creates a new thread to do some work. I can launch the new thread with no problems. When the "main" program terminates, I want the thread I created to keep running - which it does... But the problem is, when I run the main application from Eclipse or from Ant under Windows, control doesn't return unless the background process is killed. If I fork the main java process in ant, I want control to return to ant once the main thread is done with its work... But as it is, ant continues to wait until both the main process and the created thread are both terminated. How do I launch the thread in the background such that control will return to ant when the "main" application is finished? (By the way, when I run the same application under Linux, I am able to do this with no problems).

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  • Java Thread - Memory consistency errors

    - by Yatendra Goel
    I was reading a Sun's tutorial on Concurrency. But I couldn't understand exactly what memory consistency errors are? I googled about that but didn't find any helpful tutorial or article about that. I know that this question is a subjective one, so you can provide me links to articles on the above topic. It would be great if you explain it with a simple example.

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  • ID generator with local static variable - thread-safe?

    - by Poseidon
    Will the following piece of code work as expected in a multi-threaded scenario? int getUniqueID() { static int ID=0; return ++ID; } It's not necessary that the IDs to be contiguous - even if it skips a value, it's fine. Can it be said that when this function returns, the value returned will be unique across all threads?

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