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  • Does this variable need to be declared volatile?

    - by titaniumdecoy
    Does the out variable in the MyThread class need to be declared volatile in this code or will the "volatility" of the stdout variable in the ThreadTest class carry over? import java.io.PrintStream; class MyThread implements Runnable { int id; PrintStream out; // should this be declared volatile? MyThread(int id, PrintStream out) { this.id = id; this.out = out; } public void run() { try { Thread.currentThread().sleep((int)(1000 * Math.random())); out.println("Thread " + id); } catch (InterruptedException e) { e.printStackTrace(); } } } public class ThreadTest { static volatile PrintStream stdout = System.out; public static void main(String[] args) { for (int i = 0; i < 10; i++) { new Thread(new MyThread(i, stdout)).start(); } } }

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  • Access denied from another thread

    - by Lobuno
    Hello! In a program I span a thread ("the working thread"). Hera I copy some files write some data to a database and eventually, delete some other files or directories. Everything works fine. The problem is now, that I decided to move the deleting operation to some other thread. So the working thread now copies the files or directories, writes to the database, and , if there is a need to delete some other files this thread spans another thread and that second thread deleted the needed files or directories. The problem is that,the deletion used to work 100% when done in the working thread, now when the same is done in the secondary thread, I sometimes get an "Access denied" error and the files cannot be deleted. And no, the working thread is definitely NOT acceding the files and directories to delete at this moment. Sometimes (but not always) the main thread is impersonating some user, so if needed , the deleting thread is also running under impersonation just to grant the needed permissions to delete the files, so that should not be the problem. Anybody has a clue why this could be happening?

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  • Kernel thread exit in linux

    - by Raffo
    Hi guys, I'm here to ask you the difference between a process and a thread in linux. I know that a thread for linux is just a "task", which shares with the father process things that they need to have in common (the address space and other important informations). I also know that the two are creating calling the same function ('clone()'), but there's still something that I'm missing: what really happens when a thread exit? What function is called inside the linux kernel? I know that when a process exits calls the do_exit function, but here or somewhere else there should be a way to understand if it is just a thread exiting or a whole process. Can you explain me this thing or redirect to some textbook?? I tried 'Understanding the linux kernel' but I was not satisfied with it. I'm asking this thing because a need to add things to the task_struct struct, but I need to discriminate how to manage those informations for a process and its children. Thank you.

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  • What's the life-time of a thread-local value in Python?

    - by Carlos Valiente
    import threading mydata = threading.local() def run(): # When will the garbage collector be able to destroy the object created # here? After the thread exits from ``run()``? After ``join()`` is called? # Or will it survive the thread in which it was created, and live until # ``mydata`` is garbage-collected? mydata.foo = object() t = threading.Thread(target=run) t.start() t.join()

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  • Should I thread this?

    - by Psytronic
    I've got a "Loading Progress" WPF form which I instantiate when I start loading some results into my Main Window, and every time a result is loaded I want the progress bar to fill up by x amount (Based on the amount of results I'm loading). However what happens is that the Progress bar in the window stays blank the entire time, until the results have finished loading, then it will just display the full progress bar. Does this need threading to work properly? Or is it just to do with the way I'm trying to get it to work? //code snippet LoadingProgress lp = new LoadingProgress(feedCount); lp.Show(); foreach (FeedConfigGroup feed in _Feeds) { feed.insertFeeds(lp); } //part of insertFeeds(LoadingProgress lbBox) foreach (Feeds fd in _FeedSource) { lpBox.setText(fd.getName); XmlDocument feedResults = new XmlDocument(); feedResults.PreserveWhitespace = false; try { feedResults.Load(wc.OpenRead(fd.getURL)); } catch (WebException) { lpBox.addError(fd.getName); } foreach (XmlNode item in feedResults.SelectNodes("/rss/channel/item")) { //code for processing the nodes... } lpBox.progressIncrease(); } If more code is needed let me know.

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  • performSelectorInBackground, notify other viewcontroller when done.

    - by Michiel
    Hi, I have a method used to save an image when the user clicks Save. I use performSelectorInBackground to save the image, the viewcontroller is popped and the previous viewcontroller is shown. I want the table (on the previousUIViewController) to reload its data when the imagesaving is done. How can I do this? The save method is called like this: [self performSelectorInBackground:@selector(saveImage) withObject:nil]; [self.navigationController popViewControllerAnimated:YES];

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  • MFC/CCriticalSection: Simple lock situation hangs

    - by raph.amiard
    I have to program a simple threaded program with MFC/C++ for a uni assignment. I have a simple scenario in wich i have a worked thread which executes a function along the lines of : UINT createSchedules(LPVOID param) { genProgThreadVal* v = (genProgThreadVal*) param; // v->searcherLock is of type CcriticalSection* while(1) { if(v->searcherLock->Lock()) { //do the stuff, access shared object , exit clause etc.. v->searcherLock->Unlock(); } } PostMessage(v->hwnd, WM_USER_THREAD_FINISHED , 0,0); delete v; return 0; } In my main UI class, i have a CListControl that i want to be able to access the shared object (of type std::List). Hence the locking stuff. So this CList has an handler function looking like this : void Ccreationprogramme::OnLvnItemchangedList5(NMHDR *pNMHDR, LRESULT *pResult) { LPNMLISTVIEW pNMLV = reinterpret_cast<LPNMLISTVIEW>(pNMHDR); if((pNMLV->uChanged & LVIF_STATE) && (pNMLV->uNewState & LVNI_SELECTED)) { searcherLock.Lock(); // do the stuff on shared object searcherLock.Unlock(); // do some more stuff } *pResult = 0; } The searcherLock in both function is the same object. The worker thread function is passed a pointer to the CCriticalSection object, which is a member of my dialog class. Everything works but, as soon as i do click on my list, and so triggers the handler function, the whole program hangs indefinitely.I tried using a Cmutex. I tried using a CSingleLock wrapping over the critical section object, and none of this has worked. What am i missing ?

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  • Why is run() not immediately called when start() called on a thread object in java

    - by pi
    Or is it? I have a thread object from: Thread myThread = new Thread(pObject); Where pObject is an object of a class implementing the Runnable interface and then I have the start method called on the thread object like so: myThread.start(); Now, my understanding is that when start() is called, the JVM implicitly (and immediately) calls the run() method which may be overridden (as it is in my case) However, in my case, it appears that the start() method is not called immediately (as desired) but until the other statements/methods are completed from the calling block i.e. if I had a method after the start() call like so: myThread.start(); doSomethingElse(); doSomthingElse() gets executed before the run() method is run at all. Perhaps I am wrong with the initial premise that run() is always called right after the start() is called. Please help! The desired again is making executing run() right after start(). Thanks.

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  • How to execute task for a specific period in Java.?

    - by Zakaria
    In fact I would execute a specific task( a set of instructions) for a determined period. For example : I want my program to execute the task for 5 minutes, if it gets the right result it stops , else it will continue executing normal task for the 5 minutes and in the end it tells me. How can I implement this in Java.

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  • waiting for 2 different events in a single thread

    - by João Portela
    component A (in C++) - is blocked waiting for alarm signals (not relevant) and IO signals (1 udp socket). has one handler for each of these. component B (java) - has to receive the same information the component A udp socket receives. periodicaly gives instructions that should be sent through component A udp socket. How to join both components? it is strongly desirable that: the changes to attach component B to component A are minimal (its not my code and it is not very pleasent to mess with). the time taken by the new operations (usually communicating with component B) interfere very little with the usual processing time of component A - this means that if the operations are going to take a "some" time I would rather use a thread or something to do them. note: since component A receives udp packets more frequently that it has component B instructions to forward, if necessary, it can only forward the instructions (when available) from the IO handler. my initial ideia was to develop a component C (in C++) that would sit inside the component A code (is this called an adapter?) that when instanciated starts the java process and makes the necessary connections (that not so little overhead in the initialization is not a problem). It would have 2 stacks, one for the data to give component B (lets call it Bstack) and for the data to give component A (lets call it Astack). It would sit on its thread (lets call it new-thread) waiting for data to be available in Bstack to send it over udp, and listen on the udp socket to put data on the Astack. This means that the changes to component A are only: when it receives a new UDP packet put it on the Bstack, and if there is something on the Astack sent it over its UDP socket (I decided for this because this socket would only be used in the main thread). One of the problems is that I don't know how to wait for both of these events at the same time using only one thread. so my questions are: Do I really need to use the main thread to send the data over component A socket or can I do it from the new-thread? (I think the answer is no, but I'm not sure about race conditions on sockets) how to I wait for both events? boost::condition_variable or something similar seems the solution in the case of the stack and boost::asio::io_service io_service.run() seems like the thing to use for the socket. Is there any other alternative solution for this problem that I'm not aware of? Thanks for reading this long text but I really wanted you to understand the problem.

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  • how to call the method in thread with aruguments and return some value

    - by ratty
    i like to call the method in thread with aruguments and return some value here example class Program { static void Main() { Stopwatch stop = new Stopwatch(); stop.Start(); Thread FirstThread = new Thread(new ThreadStart(Fun1)); Thread SecondThread = new Thread(new ThreadStart(Fun2)); FirstThread.Start(); SecondThread.Start(); } public static void Fun1() { for (int i = 1; i <= 1000; i++) { Console.WriteLine("Fun1 writes:{0}", i); } } public static void Fun2() { for (int i = 1000; i >= 6; i--) { Console.WriteLine("Fun2 writes:{0}", i); } } } i know this above example run successfully but if method fun1 like this public int fun1(int i) { for (int n = i; n >= i+10; n++) { Console.WriteLine("Fun2 writes:{0}", i); } } then how can i call this in thread. Is it possible .Any body Help for me

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  • Stopping function on event in vb.net

    - by afilatun
    I have a vb.net application which does some processing. This processing can take a while. The application doesn't respond until the processing has ended and then it handle all events (such as click on buttons) that the user has done during the processing. I'd like to add a "Stop" button so that the user can stop the processing at some point. How can I do that? Could threading the processing (which is done in a function of the application) be a possible solution? I tried to add a button which change a boolean value and putting the code of the processing function inside a while statement based on that boolean value. However it doesn't work because the click event on the button is processed only after the end of the processing.

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  • How to change label content with timers throwing InvalidOperationException.

    - by Guru
    Hi there, I'm making an application and I'm using a timer in that application to change label content in WPF C# .NET. In timer elapsed event I'm writing the following code lblTimer.Content = "hello"; but its throwing an InvalidOperationException and gives a message "The calling thread cannot access this object because a different thread owns it." I'm using .NET framework 3.5 and WPF with C#. Please help me. Thanks in advance.

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  • Final enum in Thread's run() method

    - by portoalet
    Hi, Why is the Elvis elvis definition has to be final to be used inside the Thread run() method? Elvis elvis = Elvis.INSTANCE; // ----> should be final Elvis elvis = Elvis.INSTANCE elvis.sing(4); Thread t1 = new Thread( new Runnable() { @Override public void run() { elvis.sing(6); // --------> elvis has to be final to compile } } ); public enum Elvis { INSTANCE(2); Elvis() { this.x = new AtomicInteger(0); } Elvis(int x){ this.x = new AtomicInteger(x); } private AtomicInteger x = new AtomicInteger(0); public int getX() { return x.get(); } public void setX(int x) {this.x = new AtomicInteger(x);} public void sing(int x) { this.x = new AtomicInteger(x); System.out.println("Elvis singing.." + x); } }

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  • In .NET, what thread will Events be handled in?

    - by Ben
    I have attempted to implement a producer/consumer pattern in c#. I have a consumer thread that monitors a shared queue, and a producer thread that places items onto the shared queue. The producer thread is subscribed to receive data...that is, it has an event handler, and just sits around and waits for an OnData event to fire (the data is being sent from a 3rd party api). When it gets the data, it sticks it on the queue so the consumer can handle it. When the OnData event does fire in the producer, I had expected it to be handled by my producer thread. But that doesn't seem to be what is happening. The OnData event seems as if it's being handled on a new thread instead! Is this how .net always works...events are handled on their own thread? Can I control what thread will handle events when they're raised? What if hundreds of events are raised near-simultaneously...would each have its own thread?

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  • C# Step by Step Execution

    - by Sheldon
    Hi. I'm building an app that uses and scanner API and a image to other format converter. I have a method (actually a click event) that do this: private void ButtonScan&Parse_Click(object sender, EventArgs e) { short scan_result = scanner_api.Scan(); if (scan_result == 1) parse_api.Parse(); // This will check for a saved image the scanner_api stores on disk, and then convert it. } The problem is that the if condition (scan_result == 1) is evaluated inmediatly, so it just don't work. How can I force the CLR to wait until the API return the convenient result. NOTE Just by doing something like: private void ButtonScan&Parse_Click(object sender, EventArgs e) { short scan_result = scanner_api.Scan(); MessageBox.Show("Result = " + scan_result); if (scan_result == 1) parse_api.Parse(); // This will check for a saved image the scanner_api stores on disk, and then convert it. } It works and display the results. Is there a way to do this, how? Thank you very much!

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  • Unmanaged Process in Mono

    - by Residuum
    I want to start a quite expensive process (jackd) from a Mono application, and do not need full access to the process from the application itself. As the process is so expensive in terms of CPU usage, a Glib.IdleHandler for polling the process will not work, as it is never executed, and the GUI becomes unresponsive. Is there any way to have the cake and eating it at the same time in Mono? EDIT: I only need to be able to start and stop the process from Mono, I do not need information about the state of the process or if it has exited, as my application will register itself as a client to jackd, basically I need a "replacement" for bash's jackd &>/dev/null 2>&1 & for the System.Diagnostics.Process ;). Here is what I have so far for starting and stopping the process: public void StartJackd() { _jackd = new Process (); _jackd.StartInfo = _jackdStartup; if (_jackd.Start ()) { _jackd.EnableRaisingEvents = true; _jackd.Exited += JackdExited; } } public void StopJackd() { if (_jackd != null && !_jackd.HasExited) { _jackd.CloseMainWindow (); } } And somewhere else I have this code for registering the IdleHandler: GLib.Idle.Add(new GLib.IdleHandler(UpdateJackdConnections)); This handler will fire all the time, while the process is not running, but never, when jackd is running.

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  • Stopping looping thread in Java

    - by halfwarp
    I'm using a thread that is continuously reading from a queue. Something like: public void run() { Object obj; while(true) { synchronized(objectsQueue) { if(objectesQueue.isEmpty()) { try { objectesQueue.wait(); } catch (InterruptedException e) { e.printStackTrace(); } obj = objectesQueue.poll(); } } // Do something with the Object obj } } What is the best way to stop this thread? I see two options: 1 - Since Thread.stop() is deprecated, I can implement a stopThisThread() method that uses a n atomic check-condition variable. 2 - Send a Death Event object or something like that to the queue. When the thread fetches a death event it exists. I prefer the 1st way, however, I don't know when to call the stopThisThread() method, as something might be on it's way to the queue and the stop signal can arrive first (not desirable). Any suggestions?

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  • Execute another program in multi-threaded program

    - by Gary
    Hi, Just wondering how if it's possible to execute another program in a thread and send information to/get information from it. Essentially the same concept as with a child process and using pipes to communicate - however I don't want to use fork. I can't seem to find whether it's possible to do this, any help would be appreciated. Thanks

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  • Multi-threaded downloader in C# question

    - by blez
    Currently I have multi-threaded downloader class that uses HttpWebRequest/Response. All works fine, it's super fast, BUT.. the problem is that the data needs to be streamed while it's downloading to another app. That means that it must be streamed in the right order, the first chunk first, and then the next in the queue. Currently my downloader class is sync and Download() returns byte[]. In my async multi-threaded class I make for example, list with 4 empty elements (for slots) and I pass each index of the slot to each thread using the Download() function. That simulates synchronization, but that's not what I need. How should I do the queue thing, to make sure the data is streamed as soon as the first chunk start downloading.

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  • How refresh a DrawingArea in PyGTK ?

    - by Lialon
    I have an interface created with Glade. It contains a DrawingArea and buttons. I tried to create a Thread to refresh every X time my Canva. After a few seconds, I get error messages like: "X Window Server 0.0", "Fatal Error IO 11" Here is my code : import pygtk pygtk.require("2.0") import gtk import Canvas import threading as T import time import Map gtk.gdk.threads_init() class Interface(object): class ThreadCanvas(T.Thread): """Thread to display the map""" def __init__(self, interface): T.Thread.__init__(self) self.interface = interface self.started = True self.start() def run(self): while self.started: time.sleep(2) self.interface.on_canvas_expose_event() def stop(self): self.started = False def __init__(self): self.interface = gtk.Builder() self.interface.add_from_file("interface.glade") #Map self.map = Map.Map(2,2) #Canva self.canvas = Canvas.MyCanvas(self.interface.get_object("canvas"),self.game) self.interface.connect_signals(self) #Thread Canvas self.render = self.ThreadCanvas(self) def on_btnChange_clicked(self, widget): #Change map self.map.change() def on_interface_destroy(self, widget): self.render.stop() self.render.join() self.render._Thread__stop() gtk.main_quit() def on_canvas_expose_event(self): st = time.time() self.canvas.update(self.map) et = time.time() print "Canvas refresh in : %f times" %(et-st) def main(self): gtk.main() How can i fix these errors ?

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  • Running processes at different times stops events from working - C

    - by Jamie Keeling
    Hello, This is a question which follows on from my previously answered question here At first I assumed I had a problem with the way I was creating my events due to the handles for OpenEvent returning NULL, I have managed to find the real cause however I am not sure how to go about it. Basically I use Visual Studio to launch both Process A and B at the same time, in the past my OpenEvent handle wouldn't work due to Process A looking for the address of the event a fraction of a second before Process B had time to make it. My solution was to simply allow Process B to run before Process A, fixing the error. The problem I have now is that Process B now reads events from Process A and as you expect it too returns a null handle when trying to open the events from Process A. I am creating the events in WM_CREATE message of both processes, furthermore I also create a thread at the same time to open/read/act upon the events. It seems if I run them at the same time they don't get chance to see each other, alternatively if I run one before the other one of them misses out and can't open a Handle. Can anyone suggest a solution? Thanks.

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