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  • Wait between tasks with SingleThreadExecutor

    - by Lord.Quackstar
    I am trying to (simply) make a blocking thread queue, where when a task is submitted the method waits until its finished executing. The hard part though is the wait. Here's my 12:30 AM code that I think is overkill: public void sendMsg(final BotMessage msg) { try { Future task; synchronized(msgQueue) { task = msgQueue.submit(new Runnable() { public void run() { sendRawLine("PRIVMSG " + msg.channel + " :" + msg.message); } }); //Add a seperate wait so next runnable doesn't get executed yet but //above one unblocks msgQueue.submit(new Runnable() { public void run() { try { Thread.sleep(Controller.msgWait); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } }); } //Block until done task.get(); } catch (ExecutionException e) { log.error("Couldn't schedule send message to be executed", e); } catch (InterruptedException e) { log.error("Wait to send message interupted", e); } } As you can see, there's alot of extra code there just to make it wait 1.7 seconds between tasks. Is there an easier and cleaner solution out there or is this it?

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  • C# BackgroundWorker RunWorkerCompleted Event

    - by Jim Fell
    My C# application has several background workers. Sometimes one background worker will fire off another. When the first background worker completes and the RunWorkerCompleted event is fired, on which thread will that event fire, the UI or the first background worker from which RunWorkerAsync was called? I am using Microsoft Visual C# 2008 Express Edition. Any thoughts or suggestions you may have would be appreciated. Thanks.

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  • TerminateProcess and deadlocks

    - by Tony
    Is it real that the TerminateProcess function in Windows could hang because the threads inside the process were stuck in a deadlock? Example: Process A is running under Process B's control, now Process A gets into a deadlock and Process B detects this and decides to 'Kill' process A using TerminateProcess. Would it be successful in killing the hung Process A?

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  • Does Monitor.Wait ensure that fields are re-read?

    - by Marc Gravell
    It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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  • Push notification or thread with timer

    - by neha
    Hi all, In my application, I'm having functionality like twitter that when you have not refreshed your screen, and if there're new messages then you get this message that "You have n new messages" and a refresh button, which on press will refresh the screen. I'm basically fetching all the data from an xml with some url. In case of thread, I need to call a timer after some time period which might affect the app performance. Can anybody please suggest wheather what will be better to use push notifications or thread with timer? Thanx in advance.

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  • Is my way of doing threads in Android correct?

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

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  • Python Terminated Thread Cannot Restart

    - by Mel Kaye
    Hello, I have a thread that gets executed when some action occurs. Given the logic of the program, the thread cannot possibly be started while another instance of it is still running. Yet when I call it a second time, I get a "RuntimeError: thread already started" error. I added a check to see if it is actually alive using the Thread.is_alive() function, and it is actually dead. What am I doing wrong? I can provide more details as are needed.

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  • How to handle feedback from background threads if the user uses the back button?

    - by Janusz
    I have the following problem: I have an Activity where a user can start a web search showing a new activity to show a progress bar until the results are shown. Now the user can either wait for the results or maybe think about the search parameters, hit the back button and triggering a new search. The search is running in an Async Task and therefor still running if the user hits back. At the moment the thread finishes it calls some methods on the old activity causing the activity to show a dialog. This causes the system to crash because the dialog tries to show itself with a reference to an activity that is not longer present on the screen. How can I achieve a dialog that is only shown if the activity is still active?

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  • Thread pool stack security issue

    - by elmatador
    In a naive implementation of a thread pool, can a piece of code that is being executed read the data left by some previous code on the stack (if it was running on the same thread instance)? Also, are there any other inherent security issues connected to thread pools?

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  • Run sub on main thread from separate thread [VB.NET|SerialPort]

    - by Steven
    I'm reading data from a serial port, but the DataReceived event of SerialPort is handled on it's own thread. I want to handle this on the main thread, but simply declaring an event and raising it still results in it being processed on the SerialPort thread. I'm assuming I need to declare a delegate I can call, but I don't see how that would work. For example, I want to call Sub HandleDataReceived() on the main thread from the DataReceived thread, having HandleDataReceived() run on the main thread. How would I do this?

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  • C# Asynchronous Sockets questions.

    - by ccppjava
    Based on my reading and testing, with asynchronous sockets, the socket itself can be passed using state object (IAsyncResult result), also if store the socket as a private field, it would be captured by the callback methods. I am wondering how the IAysnResult is kepted between the BeginXXX and ReceiveXXX? It looks to me that after the BeginXXX call and the method ends, the state object would be disposed by GC if there is no reference to it. In the case of private field, how the private field is shared between threads? (As far as I know, a callback is executed using a thread from the default thread pool, which would be considered as a new thread.) Many thanks, hope the questions themselves are clear.

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  • boost::this_thread::disable_interruption usage confusion

    - by Evgenii
    boost/thread/pthread/shared_mutex.hpp contains this code: ... #include <boost/thread/detail/thread_interruption.hpp> ... class shared_mutex { ... void lock_shared() { boost::this_thread::disable_interruption do_not_disturb; boost::mutex::scoped_lock lk(state_change); while(state.exclusive || state.exclusive_waiting_blocked) { shared_cond.wait(lk); } ++state.shared_count; } ... }; but boost/thread/detail/thread_interruption.hpp does not contain implementation of disable_interruption, only the prototype. in boost_1_42_0/libs/thread/src/pthread we don't have the implementation too how does it work!???

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  • Painting on GtkScrolledWindow or GtkEventBox

    - by ptomato
    Using GTK, I'm trying to overlay a "More" prompt (but it could just as well be any drawing object) in the corner of a GtkTextView contained within a GtkScrolledWindow. I draw the prompt in the handler for the expose signal of the text view. It works, but when I scroll the window I get artifacts: the prompt is moved along with the contents of the text view and not erased. In order to get rid of the artifacts I trigger a redraw after each scroll. This mostly works, but you can still see the prompt jumping up and down when you scroll quickly. Is there any way to prevent this? It would be nice if the prompt just "floated" on top of the text view. I tried enclosing the scrolled window in a GtkEventBox and painting the prompt on top of that, but that didn't work either; the scrollbars and text view always paint over the prompt, even when you set the event box's window to go in front of its children's windows. UPDATE If I connect the GtkEventBox's expose callback with g_signal_connect_after(), then it is called after the expose callbacks of the GtkScrolledWindow and GtkTextView. The text view still draws over the event box though. I think this is because the scrolling happens asynchronously. Anybody got any idea how I can prevent my drawing from being overwritten?

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  • In C# ,how do I terminate a thread that has had its call stack corrupted?

    - by Emil D
    I have a thread in my application that is running code that can potentially cause call stack corruption ( my application is a testing tool for dlls ). Assuming that I have a method of detecting if the child thread is misbehaving, how would I terminate it? From what I read, calling Thread.Abort() on the misbehaving thread would be equivalent to raising an exception inside it.I fear that that not be a good idea, provided the call stack of the thread might be corrupted.Any suggestions?

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  • Multithreading: Read from / write to a pipe

    - by Tero Jokinen
    I write some data to a pipe - possibly lots of data and at random intervals. How to read the data from the pipe? Is this ok: in the main thread (current process) create two more threads (2, 3) the second thread writes sometimes to the pipe (and flush-es the pipe?) the 3rd thread has infinite loop which reads the pipe (and then sleeps for some time) Is this so far correct? Now, there are a few thing I don't understand: do I have to lock (mutex?) the pipe on write? IIRC, when writing to pipe and its buffer gets full, the write end will block until I read the already written data, right? How to check for read data in the pipe, not too often, not too rarely? So that the second thread wont block? Is there something like select for pipes? It is possible to set the pipe to unbuffered more or I have to flush it regularly - which one is better? Should I create one more thread, just for flushing the pipe after write? Because flush blocks as well, when the buffer is full, right? I just don't want the 1st and 2nd thread to block.... [Edit] Sorry, I thought the question is platform agnostic but just in case: I'm looking at this from Win32 perspective, possibly MinGW C...

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  • Problem using GDI+ with multiple threads (VB.NET)

    - by Joe B
    I think it would be best if I just copy and pasted the code (it's very trivial). Private Sub Main() Handles MyBase.Shown timer.Interval = 10 timer.Enabled = True End Sub Private Sub Form1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint e.Graphics.DrawImage(image, 0, 0) End Sub Private Sub tick() Handles timer.Elapsed Using g = Graphics.FromImage(image) g.Clear(Color.Transparent) g.DrawLine(Pens.Red, 0 + i, 0 + i, Me.Width - i, Me.Height - i) End Using Me.Invalidate() End Sub An exception, "The object is currently in use elsewhere", is raised during the tick event. Could someone tell me why this happens and how to solve it? Thanks.

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  • How does lock(syncRoot) make sense on a static method?

    - by Rising Star
    The following code is excerpted from the (Windows Identity Foundation SDK) template that MS uses to create a new Security Token Service Web Site. public static CustomSecurityTokenServiceConfiguration Current { get { HttpApplicationState httpAppState = HttpContext.Current.Application; CustomSecurityTokenServiceConfiguration customConfiguration = httpAppState.Get( CustomSecurityTokenServiceConfigurationKey ) as CustomSecurityTokenServiceConfiguration; if ( customConfiguration == null ) { lock ( syncRoot ) { customConfiguration = httpAppState.Get( CustomSecurityTokenServiceConfigurationKey ) as CustomSecurityTokenServiceConfiguration; if ( customConfiguration == null ) { customConfiguration = new CustomSecurityTokenServiceConfiguration(); httpAppState.Add( CustomSecurityTokenServiceConfigurationKey, customConfiguration ); } } } return customConfiguration; } } I'm relatively new to multi-threaded programming. I assume that the reason for the lock statement is to make this code thread-safe in the event that two web requests arrive at the web site at the same time. However, I would have thought that using lock (syncRoot) would not make sense because syncRoot refers to the current instance that this method is operating on... but this is a static method? How does this make sense?

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  • Best approach to synchronising properties across threads

    - by user290796
    Hi, I'm looking for some advice on the best approach to synchronising access to properties of an object in C++. The application has an internal cache of objects which have 10 properties. These objects are to be requested in sets which can then have their properties modified and be re-saved. They can be accessed by 2-4 threads at any given time but access is not intense so my options are: Lock the property accessors for each object using a critical section. This means lots of critical sections - one for each object. Return copies of the objects when requested and have an update function which locks a single critical section to update the object properties when appropriate. I think option 2 seems the most efficient but I just want to see if I'm missing a hidden 3rd option which would be more appropriate. Thanks, J

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  • emit signal from thread

    - by Umesha MS
    Hi, I am writing a sample which uses thread to do some background processing. In the thread I am trying to emitting a signal. But it is not coming to slot. While connecting I checked the value of “connect()” function value , it is returning value as true. One thing to notice is in the run method I am not using “exec() “ . Please help me to solve this problem.

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  • Structured Storage

    - by user342735
    Hi All, I have a file that is in structured storage format. I was wondering if this format be accessed concurrently by threads. Meaning have multiple threads read the different streams process it at once. The objective is to load the file faster. When i refer to a file i refer one that represents CAD information. Thank you.

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  • In C# or .NET, is there a way to prevent other threads from invoking methods on a particular thread?

    - by YWE
    I have a Windows Forms application with a BackgroundWorker. In a method on the main form, a MessageBox is shown and the user must click the OK button to continue. Meanwhile, while the messagebox is being displayed, the BackgroundWorker finishes executing and calls the RunWorkerCompleted event. In the method I have assigned to that event, which runs on the UI thread, the Close method is called on the form. Even though the method that shows the message box is still running, the UI thread is not blocking other threads from invoking methods on it. So the Close method gets called on the form. What I want is for the UI thread to block other threads' invokes until the method with the message box has finished. Is there an easy way to do that?

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  • On-Demand Python Thread Start/Join Freezing Up from wxPython GUI

    - by HokieTux
    I'm attempting to build a very simple wxPython GUI that monitors and displays external data. There is a button that turns the monitoring on/off. When monitoring is turned on, the GUI updates a couple of wx StaticLabels with real-time data. When monitoring is turned off, the GUI idles. The way I tried to build it was with a fairly simple Python Thread layout. When the 'Start Monitoring' button is clicked, the program spawns a thread that updates the labels with real-time information. When the 'Stop Monitoring' button is clicked, thread.join() is called, and it should stop. The start function works and the real-time data updating works great, but when I click 'Stop', the whole program freezes. I'm running this on Windows 7 64-bit, so I get the usual "This Program has Stopped Responding" Windows dialog. Here is the relevant code: class MonGUI(wx.Panel): def __init__(self, parent): wx.Panel.__init__(self, parent) ... ... other code for the GUI here ... ... # Create the thread that will update the VFO information self.monThread = Thread(None, target=self.monThreadWork) self.monThread.daemon = True self.runThread = False def monThreadWork(self): while self.runThread: ... ... Update the StaticLabels with info ... (This part working) ... # Turn monitoring on/off when the button is pressed. def OnClick(self, event): if self.isMonitoring: self.button.SetLabel("Start Monitoring") self.isMonitoring = False self.runThread = False self.monThread.join() else: self.button.SetLabel("Stop Monitoring") self.isMonitoring = True # Start the monitor thread! self.runThread = True self.monThread.start() I'm sure there is a better way to do this, but I'm fairly new to GUI programming and Python threads, and this was the first thing I came up with. So, why does clicking the button to stop the thread make the whole thing freeze up?

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  • Built in background-scheduling system in .NET?

    - by Lasse V. Karlsen
    I ask though I doubt there is any such system. Basically I need to schedule tasks to execute at some point in the future (usually no more than a few seconds or possibly minutes from now), and have some way of cancelling that request unless too late. Ie. code that would look like this: var x = Scheduler.Schedule(() => SomethingSomething(), TimeSpan.FromSeconds(5)); ... x.Dispose(); // cancels the request Is there any such system in .NET? Is there anything in TPL that can help me? I need to run such future-actions from various instances in a system here, and would rather avoid each such class instance to have its own thread and deal with this. Also note that I don't want this (or similar, for instance through Tasks): new Thread(new ThreadStart(() => { Thread.Sleep(5000); SomethingSomething(); })).Start(); There will potentially be a few such tasks to execute, they don't need to be executed in any particular order, except for close to their deadline, and it isn't vital that they have anything like a realtime performance concept. I just want to avoid spinning up a separate thread for each such action.

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  • Are breakpoints introduce delay?

    - by kamilo
    How is that setting a breakpoint in my code allows the following code to complete which would fail otherwise. Here is the problem. I'm writing an add-on for SAP B1 and encountered following problem. When I load a form I would like to enter some values into the form' matrix. But without a breakpoint (set on a method in which loading a form takes place) the part of code that is executed afterwards will fail. That part of code is referencing a matrix that is not yet displayed which results in an exception. This is all clear. But why setting a breakpoint "solves" the problem. What is going on? I suspect that my breakpoint introduces some delay between loading and displaying my form and part of code that references element of that form but I could be wrong. Thanks in advance

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