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• How to copy DispatcherObject (BitmapSource) into different thread?

  - by Tomáš Kafka

  Hi, I am trying to figure out how can I copy DispatcherObject (in my case BitmapSource) into another thread. Use case: I have a WPF app that needs to show window in a new thread (the app is actually Outlook addin and we need to do this because Outlook has some hooks in the main UI thread and is stealing certain hotkeys that we need to use - 'lost in translation' in interop of Outlook, WPF (which we use for UI), and Winforms (we need to use certain microsoft-provided winforms controls)). With that, I have my implementation of WPFMessageBox, that is configured by setting some static properties - and and one of them is BitmapSource for icon. This is used so that in startup I can set WPFMessageBox.Icon once, and since then, every WPFMessageBox will have the same icon. The problem is that BitmapSource, which is assigned into icon, is a DispatcherObject, and when read, it will throw InvalidOperationException: "The calling thread cannot access this object because a different thread owns it.". How can I clone that BitmapSource into the actual thread? It has Clone() and CloneCurrentValue() methods, which don't work (they throw the same exception as well). It also occured to me to use originalIcon.Dispatcher.Invoke( do the cloning here ) - but the BitmapSource's Dispatcher is null, and still - I'd create a copy on a wrong thread and still couldnt use it on mine. BitmapSource.IsFrozen == true. Any idea on how to copy the BitmapSource into different thread (without completely reconstructing it from an image file in a new thread)? EDIT: So, freezing does not help: In the end I have a BitmapFrame (Window.Icon doesn't take any other kind of ImageSource anyway), and when I assign it as a Window.Icon on a different thread, even if frozen, I get InvalidOperationException: "The calling thread cannot access this object because a different thread owns it." with a following stack trace: WindowsBase.dll!System.Windows.Threading.Dispatcher.VerifyAccess() + 0x4a bytes WindowsBase.dll!System.Windows.Threading.DispatcherObject.VerifyAccess() + 0xc bytes PresentationCore.dll!System.Windows.Media.Imaging.BitmapDecoder.Frames.get() + 0xe bytes PresentationFramework.dll!MS.Internal.AppModel.IconHelper.GetIconHandlesFromBitmapFrame(object callingObj = {WPFControls.WPFMBox.WpfMessageBoxWindow: header}, System.Windows.Media.Imaging.BitmapFrame bf = {System.Windows.Media.Imaging.BitmapFrameDecode}, ref MS.Win32.NativeMethods.IconHandle largeIconHandle = {MS.Win32.NativeMethods.IconHandle}, ref MS.Win32.NativeMethods.IconHandle smallIconHandle = {MS.Win32.NativeMethods.IconHandle}) + 0x3b bytes > PresentationFramework.dll!System.Windows.Window.UpdateIcon() + 0x118 bytes PresentationFramework.dll!System.Windows.Window.SetupInitialState(double requestedTop = NaN, double requestedLeft = NaN, double requestedWidth = 560.0, double requestedHeight = NaN) + 0x8a bytes PresentationFramework.dll!System.Windows.Window.CreateSourceWindowImpl() + 0x19b bytes PresentationFramework.dll!System.Windows.Window.SafeCreateWindow() + 0x29 bytes PresentationFramework.dll!System.Windows.Window.ShowHelper(object booleanBox) + 0x81 bytes PresentationFramework.dll!System.Windows.Window.Show() + 0x48 bytes PresentationFramework.dll!System.Windows.Window.ShowDialog() + 0x29f bytes WPFControls.dll!WPFControls.WPFMBox.WpfMessageBox.ShowDialog(System.Windows.Window owner = {WPFControlsTest.MainWindow}) Line 185 + 0x10 bytes C#

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• Subterranean IL: The ThreadLocal type

  - by Simon Cooper

  I came across ThreadLocal<T> while I was researching ConcurrentBag. To look at it, it doesn't really make much sense. What's all those extra Cn classes doing in there? Why is there a GenericHolder<T,U,V,W> class? What's going on? However, digging deeper, it's a rather ingenious solution to a tricky problem. Thread statics Declaring that a variable is thread static, that is, values assigned and read from the field is specific to the thread doing the reading, is quite easy in .NET: [ThreadStatic] private static string s_ThreadStaticField; ThreadStaticAttribute is not a pseudo-custom attribute; it is compiled as a normal attribute, but the CLR has in-built magic, activated by that attribute, to redirect accesses to the field based on the executing thread's identity. TheadStaticAttribute provides a simple solution when you want to use a single field as thread-static. What if you want to create an arbitary number of thread static variables at runtime? Thread-static fields can only be declared, and are fixed, at compile time. Prior to .NET 4, you only had one solution - thread local data slots. This is a lesser-known function of Thread that has existed since .NET 1.1: LocalDataStoreSlot threadSlot = Thread.AllocateNamedDataSlot("slot1"); string value = "foo"; Thread.SetData(threadSlot, value); string gettedValue = (string)Thread.GetData(threadSlot); Each instance of LocalStoreDataSlot mediates access to a single slot, and each slot acts like a separate thread-static field. As you can see, using thread data slots is quite cumbersome. You need to keep track of LocalDataStoreSlot objects, it's not obvious how instances of LocalDataStoreSlot correspond to individual thread-static variables, and it's not type safe. It's also relatively slow and complicated; the internal implementation consists of a whole series of classes hanging off a single thread-static field in Thread itself, using various arrays, lists, and locks for synchronization. ThreadLocal<T> is far simpler and easier to use. ThreadLocal ThreadLocal provides an abstraction around thread-static fields that allows it to be used just like any other class; it can be used as a replacement for a thread-static field, it can be used in a List<ThreadLocal<T>>, you can create as many as you need at runtime. So what does it do? It can't just have an instance-specific thread-static field, because thread-static fields have to be declared as static, and so shared between all instances of the declaring type. There's something else going on here. The values stored in instances of ThreadLocal<T> are stored in instantiations of the GenericHolder<T,U,V,W> class, which contains a single ThreadStatic field (s_value) to store the actual value. This class is then instantiated with various combinations of the Cn types for generic arguments. In .NET, each separate instantiation of a generic type has its own static state. For example, GenericHolder<int,C0,C1,C2> has a completely separate s_value field to GenericHolder<int,C1,C14,C1>. This feature is (ab)used by ThreadLocal to emulate instance thread-static fields. Every time an instance of ThreadLocal is constructed, it is assigned a unique number from the static s_currentTypeId field using Interlocked.Increment, in the FindNextTypeIndex method. The hexadecimal representation of that number then defines the specific Cn types that instantiates the GenericHolder class. That instantiation is therefore 'owned' by that instance of ThreadLocal. This gives each instance of ThreadLocal its own ThreadStatic field through a specific unique instantiation of the GenericHolder class. Although GenericHolder has four type variables, the first one is always instantiated to the type stored in the ThreadLocal<T>. This gives three free type variables, each of which can be instantiated to one of 16 types (C0 to C15). This puts an upper limit of 4096 (163) on the number of ThreadLocal<T> instances that can be created for each value of T. That is, there can be a maximum of 4096 instances of ThreadLocal<string>, and separately a maximum of 4096 instances of ThreadLocal<object>, etc. However, there is an upper limit of 16384 enforced on the total number of ThreadLocal instances in the AppDomain. This is to stop too much memory being used by thousands of instantiations of GenericHolder<T,U,V,W>, as once a type is loaded into an AppDomain it cannot be unloaded, and will continue to sit there taking up memory until the AppDomain is unloaded. The total number of ThreadLocal instances created is tracked by the ThreadLocalGlobalCounter class. So what happens when either limit is reached? Firstly, to try and stop this limit being reached, it recycles GenericHolder type indexes of ThreadLocal instances that get disposed using the s_availableIndices concurrent stack. This allows GenericHolder instantiations of disposed ThreadLocal instances to be re-used. But if there aren't any available instantiations, then ThreadLocal falls back on a standard thread local slot using TLSHolder. This makes it very important to dispose of your ThreadLocal instances if you'll be using lots of them, so the type instantiations can be recycled. The previous way of creating arbitary thread-static variables, thread data slots, was slow, clunky, and hard to use. In comparison, ThreadLocal can be used just like any other type, and each instance appears from the outside to be a non-static thread-static variable. It does this by using the CLR type system to assign each instance of ThreadLocal its own instantiated type containing a thread-static field, and so delegating a lot of the bookkeeping that thread data slots had to do to the CLR type system itself! That's a very clever use of the CLR type system.

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• How to update off screen bitmap in a surfaceview thread

  - by DKDiveDude

  I have a Surfaceview thread and an off canvas texture bitmap that is being generated (changed), first row (line), every frame and then copied one position (line) down on regular surfaceview bitmap to make a scrolling effect, and I then continue to draw other things on top of that. Well that is what I really want, however I can't get it to work even though I am creating a separate canvas for off screen bitmap. It is just not scrolling at all. I other words I have a memory bitmap, same size as Surfaceview canvas, which I need to scroll (shift) down one line every frame, and then replace top line with new random texture, and then draw that on regular Surfaceview canvas. Here is what I thought would work; My surfaceChanged where I specify bitmap and canvasses and start thread: @Override public void surfaceCreated(SurfaceHolder holder) { intSurfaceWidth = mSurfaceView.getWidth(); intSurfaceHeight = mSurfaceView.getHeight(); memBitmap = Bitmap.createBitmap(intSurfaceWidth, intSurfaceHeight, Bitmap.Config.ARGB_8888); memCanvas = new Canvas(memCanvas); myThread = new MyThread(holder, this); myThread.setRunning(true); blnPause = false; myThread.start(); } My thread, only showing essential middle running part: @Override public void run() { while (running) { c = null; try { // Lock canvas for drawing c = myHolder.lockCanvas(null); synchronized (mSurfaceHolder) { // First draw off screen bitmap to off screen canvas one line down memCanvas.drawBitmap(memBitmap, 0, 1, null); // Create random one line(row) texture bitmap memTexture = Bitmap.createBitmap(imgTexture, 0, rnd.nextInt(intTextureImageHeight), intSurfaceWidth, 1); // Now add this texture bitmap to top of off screen canvas and hopefully bitmap memCanvas.drawBitmap(textureBitmap, intSurfaceWidth, 0, null); // Draw above updated off screen bitmap to regular canvas, at least I thought it would update (save changes) shifting down and add the texture line to off screen bitmap the off screen canvas was pointing to. c.drawBitmap(memBitmap, 0, 0, null); // Other drawing to canvas comes here } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { myHolder.unlockCanvasAndPost(c); } } } } For my game Tunnel Run. Right now I have a working solution where I instead have an array of bitmaps, size of surface height, that I populate with my random texture and then shift down in a loop for each frame. I get 50 frames per second, but I think I can do better by instead scrolling bitmap.

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• how to update UI controls in cocoa application from background thread

  - by AmitSri

  following is .m code: #import "ThreadLabAppDelegate.h" @interface ThreadLabAppDelegate() - (void)processStart; - (void)processCompleted; @end @implementation ThreadLabAppDelegate @synthesize isProcessStarted; - (void)awakeFromNib { //Set levelindicator's maximum value [levelIndicator setMaxValue:1000]; } - (void)dealloc { //Never called while debugging ???? [super dealloc]; } - (IBAction)startProcess:(id)sender { //Set process flag to true self.isProcessStarted=YES; //Start Animation [spinIndicator startAnimation:nil]; //perform selector in background thread [self performSelectorInBackground:@selector(processStart) withObject:nil]; } - (IBAction)stopProcess:(id)sender { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } - (void)processStart { int counter = 0; while (counter != 1000) { NSLog(@"Counter : %d",counter); //Sleep background thread to reduce CPU usage [NSThread sleepForTimeInterval:0.01]; //set the level indicator value to showing progress [levelIndicator setIntValue:counter]; //increment counter counter++; } //Notify main thread for process completed [self performSelectorOnMainThread:@selector(processCompleted) withObject:nil waitUntilDone:NO]; } - (void)processCompleted { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } @end I need to clear following things as per the above code. How to interrupt/cancel processStart while loop from UI control? I also need to show the counter value in main UI, which i suppose to do with performSelectorOnMainThread and passing argument. Just want to know, is there anyother way to do that? When my app started it is showing 1 thread in Activity Monitor, but when i started the processStart() in background thread its creating two new thread,which makes the total 3 thread until or unless loop get finished.After completing the loop i can see 2 threads. So, my understanding is that, 2 thread created when i called performSelectorInBackground, but what about the thrid thread, from where it got created? What if thread counts get increases on every call of selector.How to control that or my implementation is bad for such kind of requirements? Thanks

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• Inside BackgroundWorker

  - by João Angelo

  The BackgroundWorker is a reusable component that can be used in different contexts, but sometimes with unexpected results. If you are like me, you have mostly used background workers while doing Windows Forms development due to the flexibility they offer for running a background task. They support cancellation and give events that signal progress updates and task completion. When used in Windows Forms, these events (ProgressChanged and RunWorkerCompleted) get executed back on the UI thread where you can freely access your form controls. However, the logic of the progress changed and worker completed events being invoked in the thread that started the background worker is not something you get directly from the BackgroundWorker, but instead from the fact that you are running in the context of Windows Forms. Take the following example that illustrates the use of a worker in three different scenarios: – Console Application or Windows Service; – Windows Forms; – WPF. using System; using System.ComponentModel; using System.Threading; using System.Windows.Forms; using System.Windows.Threading; class Program { static AutoResetEvent Synch = new AutoResetEvent(false); static void Main() { var bw1 = new BackgroundWorker(); var bw2 = new BackgroundWorker(); var bw3 = new BackgroundWorker(); Console.WriteLine("DEFAULT"); var unspecializedThread = new Thread(() => { OutputCaller(1); SynchronizationContext.SetSynchronizationContext( new SynchronizationContext()); bw1.DoWork += (sender, e) => OutputWork(1); bw1.RunWorkerCompleted += (sender, e) => OutputCompleted(1); // Uses default SynchronizationContext bw1.RunWorkerAsync(); }); unspecializedThread.IsBackground = true; unspecializedThread.Start(); Synch.WaitOne(); Console.WriteLine(); Console.WriteLine("WINDOWS FORMS"); var windowsFormsThread = new Thread(() => { OutputCaller(2); SynchronizationContext.SetSynchronizationContext( new WindowsFormsSynchronizationContext()); bw2.DoWork += (sender, e) => OutputWork(2); bw2.RunWorkerCompleted += (sender, e) => OutputCompleted(2); // Uses WindowsFormsSynchronizationContext bw2.RunWorkerAsync(); Application.Run(); }); windowsFormsThread.IsBackground = true; windowsFormsThread.SetApartmentState(ApartmentState.STA); windowsFormsThread.Start(); Synch.WaitOne(); Console.WriteLine(); Console.WriteLine("WPF"); var wpfThread = new Thread(() => { OutputCaller(3); SynchronizationContext.SetSynchronizationContext( new DispatcherSynchronizationContext()); bw3.DoWork += (sender, e) => OutputWork(3); bw3.RunWorkerCompleted += (sender, e) => OutputCompleted(3); // Uses DispatcherSynchronizationContext bw3.RunWorkerAsync(); Dispatcher.Run(); }); wpfThread.IsBackground = true; wpfThread.SetApartmentState(ApartmentState.STA); wpfThread.Start(); Synch.WaitOne(); } static void OutputCaller(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "RunWorkerAsync".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); } static void OutputWork(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "DoWork".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); } static void OutputCompleted(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "RunWorkerCompleted".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); Synch.Set(); } } Output: //DEFAULT //bw1.RunWorkerAsync | Thread: 3 | IsThreadPool: False //bw1.DoWork | Thread: 4 | IsThreadPool: True //bw1.RunWorkerCompleted | Thread: 5 | IsThreadPool: True //WINDOWS FORMS //bw2.RunWorkerAsync | Thread: 6 | IsThreadPool: False //bw2.DoWork | Thread: 5 | IsThreadPool: True //bw2.RunWorkerCompleted | Thread: 6 | IsThreadPool: False //WPF //bw3.RunWorkerAsync | Thread: 7 | IsThreadPool: False //bw3.DoWork | Thread: 5 | IsThreadPool: True //bw3.RunWorkerCompleted | Thread: 7 | IsThreadPool: False As you can see the output between the first and remaining scenarios is somewhat different. While in Windows Forms and WPF the worker completed event runs on the thread that called RunWorkerAsync, in the first scenario the same event runs on any thread available in the thread pool. Another scenario where you can get the first behavior, even when on Windows Forms or WPF, is if you chain the creation of background workers, that is, you create a second worker in the DoWork event handler of an already running worker. Since the DoWork executes in a thread from the pool the second worker will use the default synchronization context and the completed event will not run in the UI thread.

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• How to use OpenGL functions from multiples thread?

  - by Robert

  I'm writing a small game using OpenGL. I'm implementing basic networking in this game and I'm facing a problem. I have a thread in my client socket class that check for available data, when there are data I raise an event like this : immutable int len = this.m_socket.receive(data); if(len > 0) { this.m_onDataEvent(data); } Then on my game class, I have a function that handle and parse data like this : switch(msgId) { case ProtocolID.CharacterData: // Load terrain with opengl, character model.... Im not able to call opengl functions because my opengl context is created from a different thread. But I really don't know how I can solve this problem, I tried Google but it's really hard to find a solution. I'm using D programming language if it can help.

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• Background thread in C#

  - by Xodarap

  When the user saves some data, I want to spin off a background thread to update my indexes and do some other random stuff. Even if there is an error in this indexing the user can't do anything about it, so there is no point in forcing the main thread to wait until the background thread finishes. I'm doing this from a ASP.NET process, so I think I should be able to do this (as the main thread exiting won't kill the process). When I set a breakpoint in the background thread's method though, the main thread also appears to stop. Is this just an artifact of visual studio's debugger, or is the main thread really not going to return until the background thread stops?

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• creating a thread in jsp and using join has problem

  - by Suresh S

  guys the following code does not wiat for the thread t to complete and join with the main thread, also the "created object" trace is called one more time after join is called please let me know the solution <% AProc empList = new AProc(); System.out.println("** Created Object ****"); System.out.println("Condition"+(!(p.length==0) && !(status) && !(threadLive))); if (!(p.length==0) && !(status) && !(threadLive)){ java.util.Date currDate = new java.util.Date(); try { Thread t = new Thread(empList); System.out.println("Check thread life 1 "+t.isAlive()); empList.setServletRequest(request , schemaName); System.out.println("Thread Started "+t); t.start(); System.out.println("Check thread life 2 "+t.isAlive()); if(t.isAlive()) { threadLive = true; } t.join(); while (t.isAlive()) { t.join(); } System.out.println("Check thread life 3 "+t.isAlive()); System.out.println("Thread End "+t); //} } catch (Exception e) { System.out.println("Exception in thread while running Procedure "+e); status=false; threadLive=false; } status = e.getStatusProc(); }%>

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• Starting an STA thread, but with parameters to the final function

  - by DRapp

  I'm a bit weak on how some delegates behave, such as passing a method as the parameter to be invoked. While trying to do some NUnit test scripts, I have something that I need to run many test with. Each of these tests requires a GUI created and thus the need for an STA thread. So, I have something like public class MyTest { // the Delegate "ThreadStart" is part of the System.Threading namespace and is defined as // public delegate void ThreadStart(); protected void Start_STA_Thread(ThreadStart whichMethod) { Thread thread = new Thread(whichMethod); thread.SetApartmentState(ApartmentState.STA); //Set the thread to STA thread.Start(); thread.Join(); } [Test] public void Test101() { // Since the thread issues an INVOKE of a method, I'm having it call the // corresponding "FromSTAThread" method, such as Start_STA_Thread( Test101FromSTAThread ); } protected void Test101FromSTAThread() { MySTA_RequiredClass oTmp = new MySTA_RequiredClass(); Assert.IsTrue( oTmp.DoSomething() ); } } This part all works fine... Now the next step. I now have a different set of tests that ALSO require an STA thread. However, each "thing" I need to do requires two parameters... both strings (for this case). How do I go about declaring proper delegate so I can pass in the method I need to invoke, AND the two string parameters in one shot... I may have 20+ tests to run with in this pattern and may have future of other similar tests with different parameter counts and types of parameters too. Thanks.

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• Background thread in .NET

  - by Xodarap

  When the user saves some data, I want to spin off a background thread to update my indexes and do some other random stuff. Even if there is an error in this indexing the user can't do anything about it, so there is no point in forcing the main thread to wait until the background thread finishes. I'm doing this from a ASP.NET process, so I think I should be able to do this (as the main thread exiting won't kill the process). When I set a breakpoint in the background thread's method though, the main thread also appears to stop. Is this just an artifact of visual studio's debugger, or is the main thread really not going to return until the background thread stops?

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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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• What is the event dispatching thread?

  - by Roman

  I know what "thread" means and if I understand the event dispatching thread (EDT) as "just a thread", it explains a lot but, apparently, it does not explain everything. I do not understand what is special about this thread. For example I do not understand why we should start a GUI in a the EDT? Why the "main" thread is bed for GUI? Well, if we just do not want to occupy the main thread why we cannot start GUI just in "another thread" why it should be some "special" thread called EDT? Then I do not understand why we cannot start the EDT like any other thread? Why we should use some special tool (called invokeLater). And why GUI, unlike any other thread, does not start immediately. We should wait until it is ready to accept our job. Is it because EDT can, potentially execute several task simultaneously? If you decide to answer this question, could you pleas use a really simple terminology because otherwise, I am afraid, I will not be able to understand the answer.

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• Can one thread open a socket and other thread close it?

  - by Pkp

  I have some kernel threads in Linux kernel, inside my KLM. I have a server thread, that listens to the channel, Once it sees there is an incoming connection, it creates an accept socket, accepts the connection and spawns a child thread. It also passes the accepted socket to the child kernel thread as the (void *) argument. The code is working fine. I had a design question. Suppose now the threads have to be terminated, main and the child threads, what would be the best way to close the accept socket. I can see two ways, 1] The main thread waits for all the child threads to exit, each of the child threads close the accept sockets while exiting, the last child thread passes a signal to the main thread for it to exit . Here even though the main thread was the one that created the accept socket, the child threads close that socket, and they do this before the main thread exits. So is this acceptable? Any problems you guys forsee here? 2] Second is the main thread closes all the accept sockets it created before it exits. But there may be a possibility(corner case) that the main thread gets an exception and will have to close, so if it closes the accept sockets before exiting, the child threads using that socket will be in danger. Hence i am using the first case i mentioned.Let me know what you guys think?

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• Run two shell file with thread

  - by user1149157

  How i can run two file shell in parallel and do not shared the same jvm. may be i use thread but how i run two file shell bu two thread ? File 1: #!/bin/bash # # Script for running several experimentations one the same JVM # Usage : TRACE_DIR NB_EXPE Factories... # param="parameter1" another="parameter2" for ((i = 10; i >= 0; i -= 1)) do echo "run my file with param another " done File 2 : #!/bin/bash # # Script for running several experimentations one the same JVM # Usage : TRACE_DIR NB_EXPE Factories... # a="101" b="400" c="500" echo "run my programme with a b c "

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• Why thread specific data is required in pthread ?

  - by user504542

  Hi As i know, all the threads share memory location. For example a global variable changes in one thread will reflect in another thread. Since each thread has its own stack, the local variables that are created inside the thread is unique. In this case, why do we need to go for thread specific data mechanism?. Can't it be achieved by auto storage varibles inside the thread function ? Kindly clarify!!!. BR Rj

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• Is Java class initialized by the thread which use it for the first time?

  - by oo_olo_oo

  Lets assume following classes definition: public class A { public final static String SOME_VALUE; static { SOME_VALUE = "some.value"; } } public class B { private final String value = A.SOME_VALUE; } Assuming that the class A hasn't been loaded yet, what does happen when object of the class B is instantiated by some thread T? The class A has to be loaded and instantiated first. But my question is: if it's done in context of the thread T, or rather in context of some other (special) "classloader" thread?

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• How do I create a new thread to make pcap_loop() and gtk_main() compatible?

  - by httpinterpret

  These two functions are both infinite loops, and the programe hangs once called in the same thread. gtk_main(); ... pcap_loop(adhandle, 0, packet_handler, NULL); How do I create a child thread and run pcap_loop(adhandle, 0, packet_handler, NULL); instead?

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• Is the Microsoft Enterprise Library 5.0 Logging Application Block thread safe?

  - by GiddyUpHorsey

  I have some code that will be logging using the Logging Application Block in Enterprise Library 5.0 from different threads. Is the LAB thread safe? Can I log like normal from different threads or will I need to synchronize the logging code so that is only used from one thread at a time?

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• How to change the current selection in a wxListbook from another thread?

  - by George Edison

  How can I change the current selection in a wxListbook from another thread? When I pass the listbook's pointer to the thread and try to change the selection, the app crashes. What is a safe way of doing this? Is there some message I can send to it?

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• how to make a thread of never stop, and write something to database every 10 second..

  - by zjm1126

  i using gae and django this is my code: class LogText(db.Model): content = db.StringProperty(multiline=True) class MyThread(threading.Thread): def __init__(self,threadname): threading.Thread.__init__(self, name=threadname) def run(self,request): log=LogText() log.content=request.POST.get('content',None) log.put() def Log(request): thr = MyThread('haha') thr.run(request) return HttpResponse('')

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• Do you know of some performances test of the different ways to get thread local storage in C++?

  - by Vicente Botet Escriba

  I'm doing a library that makes extensive use of a thread local variable. Can you point to some benchmarks that test the performances of the different ways to get thread local variables in C++: C++0x thread_local variables compiler extension (Gcc __thread, ...) boost::threads_specific_ptr pthread Windows ... Does C++0x thread_local performs much better on the compilers providing it?

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• Pass string between two threads in java

  - by geeta

  I have to search a string in a file and write the matched lines to another file. I have a thread to read a file and a thread to write a file. I want to send the stringBuffer from read thread to write thread. Please help me to pass this. I amm getting null value passed. write thread: class OutputThread extends Thread{ /****************** Writes the line with search string to the output file *************/ Thread runner1,runner; File Out_File; public OutputThread() { } public OutputThread(Thread runner,File Out_File) { runner1 = new Thread(this,"writeThread"); // (1) Create a new thread. this.Out_File=Out_File; this.runner=runner; runner1.start(); // (2) Start the thread. } public void run() { try{ BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(Out_File,true)); System.out.println("inside write"); synchronized(runner){ System.out.println("inside wait"); runner.wait(); } System.out.println("outside wait"); // bufferedWriter.write(line.toString()); Buffer Buf = new Buffer(); bufferedWriter.write(Buf.buffers); System.out.println(Buf.buffers); bufferedWriter.flush(); } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } } Read Thraed: class FileThread extends Thread{ Thread runner; File dir; String search_string,stats; File Out_File,final_output; StringBuffer sb = new StringBuffer(); public FileThread() { } public FileThread(CountDownLatch latch,String threadName,File dir,String search_string,File Out_File,File final_output,String stats) { runner = new Thread(this, threadName); // (1) Create a new thread. this.dir=dir; this.search_string=search_string; this.Out_File=Out_File; this.stats=stats; this.final_output=final_output; this.latch=latch; runner.start(); // (2) Start the thread. } public void run() { try{ Enumeration entries; ZipFile zipFile; String source_file_name = dir.toString(); File Source_file = dir; String extension; OutputThread out = new OutputThread(runner,Out_File); int dotPos = source_file_name.lastIndexOf("."); extension = source_file_name.substring(dotPos+1); if(extension.equals("zip")) { zipFile = new ZipFile(source_file_name); entries = zipFile.entries(); while(entries.hasMoreElements()) { ZipEntry entry = (ZipEntry)entries.nextElement(); if(entry.isDirectory()) { (new File(entry.getName())).mkdir(); continue; } searchString(runner,entry.getName(),new BufferedInputStream(zipFile.getInputStream(entry)),Out_File,final_output,search_string,stats); } zipFile.close(); } else { searchString(runner,Source_file.toString(),new BufferedInputStream(new FileInputStream(Source_file)),Out_File,final_output,search_string,stats); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } /********* Reads the Input Files and Searches for the String ******************************/ public void searchString(Thread runner,String Source_File,BufferedInputStream in,File output_file,File final_output,String search,String stats) { int count = 0; int countw = 0; int countl=0; String s; String[] str; String newLine = System.getProperty("line.separator"); try { BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); //OutputFile outfile = new OutputFile(); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(output_file,true)); Buffer Buf = new Buffer(); //StringBuffer sb = new StringBuffer(); StringBuffer sb1 = new StringBuffer(); while((s = br2.readLine()) != null ) { str = s.split(search); count = str.length-1; countw += count; if(s.contains(search)){ countl++; sb.append(s); sb.append(newLine); } if(countl%100==0) { System.out.println("inside count"); Buf.setBuffers(sb.toString()); sb.delete(0,sb.length()); System.out.println("outside notify"); synchronized(runner) { runner.notify(); } //outfile.WriteFile(sb,bufferedWriter); //sb.delete(0,sb.length()); } } } synchronized(runner) { runner.notify(); } br2.close(); in.close(); if(countw == 0) { System.out.println("Input File : "+Source_File ); System.out.println("Word not found"); System.exit(0); } else { System.out.println("Input File : "+Source_File ); System.out.println("Matched word count : "+countw ); System.out.println("Lines with Search String : "+countl); System.out.println("Output File : "+output_file.toString()); System.out.println(); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } }

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• Android Design - Service vs Thread for Networking

  - by Nevyn

  I am writing an Android app, finally (yay me) and for this app I need persistant, but user closeable, network sockets (yes, more than one). I decided to try my hand at writing my own version of an IRC Client. My design issue however, is I'm not sure how to run the Socket connectivity itself. If I put the sockets at the Activity level, they keeps getting closed shortly after the Activity becomes non-visible (also a problem that needs solving...but I think i figured that one out)...but if I run a "connectivity service", I need to find out if I can have multiple instances of it running (the service, that is...one per server/socket). Either that or a I need a way to Thread the sockets themselves and have multiple threads running that I can still communicate with directly (ID system of some sort). Thus the question: Is it a 'better', or at least more "proper" design pattern, to put the Socket and networking in a service, and have the Activities consume said service...or should I tie the sockets directly to some Threaded Process owned by the UI Activity and not bother with the service implementation at all? I do know better than to put the networking directly on the UI thread, but that's as far as I've managed to get.

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• Can Clojure's thread-based agents handle c10k performance?

  - by elliot42

  I'm writing a c10k-style service and am trying to evaluate Clojure's performance. Can Clojure agents handle this scale of concurrency with its thread-based agents? Other high performance systems seem to be moving towards async-IO/events/greenlets, albeit at a seemingly higher complexity cost. Suppose there are 10,000 clients connected, sending messages that should be appended to 1,000 local files--the Clojure service is trying to write to as many files in parallel as it can, while not letting any two separate requests mangle the same single file by writing at the same time. Clojure agents are extremely elegant conceptually--they would allow separate files to be written independently and asynchronously, while serializing (in the database sense) multiple requests to write to the same file. My understanding is that agents work by starting a thread for each operation (assume we are IO-bound and using send-off)--so in this case is it correct that it would start 1,000+ threads? Can current-day systems handle this number of threads efficiently? Most of them should be IO-bound and sleeping most of the time, but I presume there would still be a context-switching penalty that is theoretically higher than async-IO/event-based systems (e.g. Erlang, Go, node.js). If the Clojure solution can handle the performance, it seems like the most elegant thing to code. However if it can't handle the performance then something like Erlang or Go's lightweight processes might be preferable, since they are designed to have tens of thousands of them spawned at once, and are only moderately more complex to implement. Has anyone approached this problem in Clojure or compared to these other platforms? (Thanks for your thoughts!)

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• How to find out where a thread lock happend?

  - by SchlaWiener

  One of our company's Windows Forms application had a strange problem for several month. The app worked very reliable for most of our customers but on some PC's (mostly with a wireless lan connection) the app sometimes just didn't respond anymore. (You click on the UI and windows ask you to wait or kill the app). I wasn't able to track down the problem for a long time but now I figured out what happend. The app had this line of code // don't blame me for this. Wasn't my code :D Control.CheckForIllegalCrossThreadCalls = false and used some background threads to modify the controls. No I found a way to reproduce the application stopping responding bug on my dev machine and tracked it down to a line where I actually used Invoke() to run a task in the main thread. Me.Invoke(MyDelegate, arg1, arg2) Obviously there was a thread lock somewhere. After removing the Control.CheckForIllegalCrossThreadCalls = false statement and refactoring the whole programm to use Invoke() if modifying a control from a background thread, the problem is (hopefully) gone. However, I am wondering if there is a way to find such bugs without debugging every line of code (Even if I break into debugger after the app stops responding I can't tell what happend last, because the IDE didn't jump to the Invoke() statement) In other words: If my apps hangs how can I figure out which line of code has been executed last? Maybe even on the customers PC. I know VS2010 offers some backwards debugging feature, maybe that would be a solution, but currently I am using VS2008.

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