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• thread destructors in C++0x vs boost

  - by Abruzzo Forte e Gentile

  Hi All These days I am reading the pdf Designing MT programs . It explains that the user MUST explicitly call detach() on an object of class std::thread in C++0x before that object gets out of scope. If you don't call it std::terminate() will be called and the application will die. I usually use boost::thread for threading in C++. Correct me if I am wrong but a boost::thread object detaches automatically when it get out of scope. Is seems to me that the boost approach follow a RAII principle and the std doesn't. Do you know if there is some particular reason for this? Kind Regards AFG

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• Thread help with Android game

  - by Ciph3rzer0

  I need some help dealing with three Threads in Android One thread is the main thread, the other is the GLThread, and the other is a WorkerThread I created to update the game state. The problem I have is they all need to access the same LinkedList of game objects. Both the GLThread and my WorkerThread only read from the LinkedList, so no problem there, but occasionally I have the main thread adding in another game object to the list. How can I manage this? I tried using synchronized in front of the functions involved but it really slows down the application. For some reason, just catching the errors and not rendering or updating the game state that frame, causes it to start lagging permanently. Anyone have any great ideas?

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• VC++ - Asynchronous Thread

  - by JVNR

  I am working on VC++ project, in that my application process a file from input path and generates 3 output "*.DAT" files in the destination path. I will FTP these DAT file to the destination server. After FTP, I need to delete only two output .DAT files the folder. I am able to delete those files, because there one Asynchronous thread running behind the process. Since the thread is running, while deleting it says, "Cannot delete, the file is used by another person". I need to stop that thread and delete the files. Multiple files can also be taken from the input path to process. Please help me in resolving this issue. Its very high priority issue for me. Please help me ASAP.

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• efficient thread-safe singleton in C++

  - by user168715

  The usual pattern for a singleton class is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) inst = new Foo(...); return *inst; } However, it's my understanding that this solution is not thread-safe, since 1) Foo's constructor might be called more than once (which may or may not matter) and 2) inst may not be fully constructed before it is returned to a different thread. One solution is to wrap a mutex around the whole method, but then I'm paying for synchronization overhead long after I actually need it. An alternative is something like static Foo &getInst() { static Foo *inst = NULL; if(inst == NULL) { pthread_mutex_lock(&mutex); if(inst == NULL) inst = new Foo(...); pthread_mutex_unlock(&mutex); } return *inst; } Is this the right way to do it, or are there any pitfalls I should be aware of? For instance, are there any static initialization order problems that might occur, i.e. is inst always guaranteed to be NULL the first time getInst is called?

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• Update UI in the main activity through handler in a thread (Android)

  - by Hrk

  Hello, I try to make several connection in a class and update the multiple progressbar in the main screen. But I've got the following error trying to use thread in android : Code: 05-06 13:13:11.092: ERROR/ConnectionManager(22854): ERROR:Can't create handler inside thread that has not called Looper.prepare() Here is a small part of my code in the main Activity public class Act_Main extends ListActivity { private ConnectionManager cm; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set up the window layout requestWindowFeature(Window.FEATURE_CUSTOM_TITLE); setContentView(R.layout.main); getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.custom_title); } public void startConnection() { //open DB connection db = new DBAdapter(getApplicationContext()); db.open(); cm = new ConnectionManager(handler, db); showDialog(DIALOG_PROGRESS_LOGIN); } @Override public void onStart() { super.onStart(); startConnection(); } protected Dialog onCreateDialog(int id) { switch (id) { case DIALOG_PROGRESS_LOGIN: progressDialog = new ProgressDialog(Act_Main.this); progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); progressDialog.setMessage("Connecting.\nPlease wait..."); progressThreadLogin = new ProgressThreadLogin(); progressThreadLogin.start(); return progressDialog; case DIALOG_PROGRESS_NETWORK: [b]progressDialog = new ProgressDialog(Act_Main.this);[/b] progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); progressDialog.setMessage("Loading entire network.\nPlease wait..."); progressThreadNetwork = new ProgressThreadNetwork(); progressThreadNetwork.start(); return progressDialog; default: return null; } } // Define the Handler that receives messages from the thread and update the progress final Handler handler = new Handler() { public void handleMessage(Message msg) { int total = msg.getData().getInt("total"); int step = msg.getData().getInt("step"); Log.d(TAG, "handleMessage:PROCESSBAR:"+total); progressDialog.setProgress(total); if (total >= 100) { switch (step) { case UPDATE_NETWORK: dismissDialog(DIALOG_PROGRESS_LOGIN); showDialog(DIALOG_PROGRESS_NETWORK); cm.getNetwork(); break; .... default: break; } } } }; private class ProgressThreadLogin extends Thread { ProgressThreadLogin() { } public void run() { cm.login(); } } private class ProgressThreadNetwork extends Thread { ProgressThreadNetwork() { } public void run() { cm.getNetwork(); } } } And my connectionManager class: public class ConnectionManager { public ConnectionManager(Handler handler, DBAdapter db) { this.handler = handler; this.db = db; } public void updateProgressBar(int step, int value) { if (value == 0) total = total+1; else total = value ; Message msg = handler.obtainMessage(); Bundle b = new Bundle(); b.putInt("total", total); b.putInt("step", step); msg.setData(b); handler.handleMessage(msg); } public void login() { //DO MY LOGIN TASK updateProgressBar(Act_Main.UPDATE_NETWORK, 100); } } The crash errors occurs on the first line of "case DIALOG_PROGRESS_NETWORK:". My first progressbar is hidden but the second one is not displayed. I think I've done somthing wrong using the threads and handlers but I dont' know why. I was first using handler.sendMessage in place of handler.handleMessage but when I had several task in my connectionManager, the progressbar was updated only at the end of all tasks. Thank you in advance for your help

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• Illegal cross thread operation exception, unable to handle it

  - by yeah1000

  Hello, i am using visual C# express 2008. I SOMETIMES get the illegal cross thread operation in my invoke method when i try to run my project. It use the same invoke method in many places but its only at the beginning of another thread that i get the error. I check the InvokeRequired property, invoke the same method and in the 'else' condition and create a temporary variable and assign it the text of my control. But on that line, in the 'else' statement, inside the Invoking method i sometimes get the exception. What could be the cause? How to get rid of it? It does not occur often, but it is still a bug... Code: // Delegate: private delegate void ChangeTextDelegate(string text); // Method: public static void ChangeText(string text) { if (richtextbox1.InvokeRequired) { richtextbox1.Invoke(new ChangeTextDelegate(ChangeText), new object[] { text }); } else { int startIndex; startIndex = richtextbox1.TextLength; // <- Exception points here. // ... } } Stack trace: System.InvalidOperationException was unhandled Message="Cross-thread operation not valid: Control 'SomeClass' accessed from a thread other than the thread it was created on." Source="System.Windows.Forms" StackTrace: at System.Windows.Forms.Control.get_Handle() at System.Windows.Forms.Control.get_InternalHandle() at System.Windows.Forms.Control.WmWindowPosChanged(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.TextBoxBase.WndProc(Message& m) at System.Windows.Forms.RichTextBox.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam) at System.Windows.Forms.NativeWindow.DefWndProc(Message& m) at System.Windows.Forms.Control.DefWndProc(Message& m) at System.Windows.Forms.Control.WmCreate(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.TextBoxBase.WndProc(Message& m) at System.Windows.Forms.RichTextBox.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.IntCreateWindowEx(Int32 dwExStyle, String lpszClassName, String lpszWindowName, Int32 style, Int32 x, Int32 y, Int32 width, Int32 height, HandleRef hWndParent, HandleRef hMenu, HandleRef hInst, Object pvParam) at System.Windows.Forms.UnsafeNativeMethods.CreateWindowEx(Int32 dwExStyle, String lpszClassName, String lpszWindowName, Int32 style, Int32 x, Int32 y, Int32 width, Int32 height, HandleRef hWndParent, HandleRef hMenu, HandleRef hInst, Object pvParam) at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp) at System.Windows.Forms.Control.CreateHandle() at System.Windows.Forms.TextBoxBase.CreateHandle() at System.Windows.Forms.Control.get_Handle() at System.Windows.Forms.RichTextBox.get_TextLength() at SomeNamespace.SomeClass.Changetext(String text, Color color) in C:\...\SomeClass.cs:line 827 at SomeNamespace.SomeClass.SomeThreadFun() in C:\...\SomeClass.cs:line 112 at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: TY

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• Boost.Thread Linking - boost_thread vs. boost_thread-mt

  - by Robert S. Barnes

  It's not clear to me what linking options exist for the Boost.Thread 1.34.1 library. I'm on Ubuntu 8.04 and I've found that using eitherr boost_thread or boost_thread-mt during linking both compile and run, but I don't see any documentation on these or any other linking options in above link. What Boost.Thread linking options are available and what do the mean?

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• Help regarding C# thread pool

  - by Matt

  I have a method that gets called quite often, with text coming in as a parameter.. I'm looking at creating a thread pool that checks the line of text, and performs actions based on that.. Can someone help me out with the basics behind creating the thread pool and firing off new threads please? This is so damn confusing..

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• can create a new thread on goog-app-engine ..(python)

  - by zjm1126

  i use this code can crteate ,but someone say it can't create ,why ? 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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• May volatile be in user defined types to help writing thread-safe code

  - by David Rodríguez - dribeas

  I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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• Twisted: why is it that passing a deferred callback to a deferred thread makes the thread blocking a

  - by surtyaarthoughts

  I unsuccessfully tried using txredis (the non blocking twisted api for redis) for a persisting message queue I'm trying to set up with a scrapy project I am working on. I found that although the client was not blocking, it became much slower than it could have been because what should have been one event in the reactor loop was split up into thousands of steps. So instead, I tried making use of redis-py (the regular blocking twisted api) and wrapping the call in a deferred thread. It works great, however I want to perform an inner deferred when I make a call to redis as I would like to set up connection pooling in attempts to speed things up further. Below is my interpretation of some sample code taken from the twisted docs for a deferred thread to illustrate my use case: #!/usr/bin/env python from twisted.internet import reactor,threads from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(): print 'doing lookup... this may take a while' time.sleep(10) return 'results from redis' def result(res): print res def main(): lc = LoopingCall(main_loop) lc.start(2) d = threads.deferToThread(aBlockingRedisCall) d.addCallback(result) reactor.run() if __name__=='__main__': main() And here is my alteration for connection pooling that makes the code in the deferred thread blocking : #!/usr/bin/env python from twisted.internet import reactor,defer from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(x): if x<5: #all connections are busy, try later print '%s is less than 5, get a redis client later' % x x+=1 d = defer.Deferred() d.addCallback(aBlockingRedisCall) reactor.callLater(1.0,d.callback,x) return d else: print 'got a redis client; doing lookup.. this may take a while' time.sleep(10) # this is now blocking.. any ideas? d = defer.Deferred() d.addCallback(gotFinalResult) d.callback(x) return d def gotFinalResult(x): return 'final result is %s' % x def result(res): print res def aBlockingMethod(): print 'going to sleep...' time.sleep(10) print 'woke up' def main(): lc = LoopingCall(main_loop) lc.start(2) d = defer.Deferred() d.addCallback(aBlockingRedisCall) d.addCallback(result) reactor.callInThread(d.callback, 1) reactor.run() if __name__=='__main__': main() So my question is, does anyone know why my alteration causes the deferred thread to be blocking and/or can anyone suggest a better solution?

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• Is this code thread-safe?

  - by mafutrct

  I've got a class with several properties. On every value update, a Store method is called with stores all fields (in a file). private int _Prop1; public int Prop1 { get { return _Prop1; } set { _Prop1 = value; Store(); } } // more similar properties here... private XmlSerializer _Ser = new ...; private void Store() { lock (_Ser) { using (FileStream fs = new ...) { _Ser.Serialize (fs, this); } } } Is this design thread-safe? (Btw, if you can think of a more appropriate caption, feel free to edit.)

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• Android: raise AlertDialog from background thread

  - by Stefan Klumpp

  In my activity there's some stuff going on in a background thread, which gets started in Activity_1. The processing of the background thread takes a while and I want to notify the user when it's completed via an AlertDialog. However, the user might have changed to Activity_2 or Activity_3 in the meantime and I would like to pop up the AlertDialog always in the current Activity. Any idea how to realize this?

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• Thread & Windows forms

  - by Julien

  I'd like to know if the executing thread is the one that created a given control instance (to prevent cross-thread if it's not). Is that possible ?

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• What is the use of Thread.BeginThreadAffinity() method in Thread class ?

  - by DotNetBeginner

  What is the use of Thread.BeginThreadAffinity() method in Thread class ? It will be helpful for me to understand if you provide its sample example with exaplaination. Thanks.

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• Thread Management Object

  - by Gusdor

  I feel rather foolish as this is just a short question. I was reading about a bunch of thread management helper classes in .net, specifically one that aids the storage of threads to help a service manager object automatically invoke delegates onto the subscribing thread. I'm pretty sure it had something to do with creating dispatchers. Totally forgotten the name, can't find it :( Anyone know what I'm talking about?

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• Django Thread-Safety for templatetags

  - by Acti67

  Hi, I am coming here, because I have a question about Django and Thread. I read the documentation http://docs.djangoproject.com/en/dev/howto/custom-template-tags/#template-tag-thread-safety and I would like to now if the next code could be impacted also, at the rendering context. class ChatterCountNode(NodeBase): def __init__(self, channelname, varname): self.channelname = channelname self.varname = varname def render(self, context): channelname = self.getvalue(context, self.channelname) varname = self.getvalue(context, self.varname) count = get_channel_count(channelname) context[varname] = count return '' Thank you for your time. Stéphane

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• Thread affinity

  - by mita

  Can we set two thread or two task to execute with different processor affinity in C#.net Application? I have read about SetThreadAffinityMask but there is no example to have that used.. or Is there any way TPL(Task Parellel Libray) executes two thread/Task in with high priorty to use 100% cpu ?

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• redirect output from file to three running thread

  - by alaamh

  I want to use 'cat myclip.avi' command to send the output to three running thread, i am trying to process same clip file to produce three different result. can i use dup2 or how i can make pipe with thread not fork? 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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• How to use timer in a thread

  - by Anjaneyulu

  Hi, I would like to send email notifications to users of my project exactly at 8 a.m, Here we are using a thread to send emails to the user. I would like to send some emails exactly at 8 A.M. How can I execute that perticular logic in this Thread. Please help me.

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• Static dictionary in .Net Thread safety

  - by Emmanuel

  Reading msdn documentation for dictionaries it says : "Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." Those this mean that with a dictionary such as this : static object syncObject = new object(); static Dictionary<string,MyObject> mydictionary= new Dictionary<string, MyObject>(); Is doing something like the code below unnecessary? lock (syncObject) { context = new TDataContext(); mydictionary.Add("key", myObject); }

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• Thread & Windows forms (C#)

  - by Julien

  Hello, I'd like to know if the executing thread is the one that created a given control instance (to prevent cross-thread if it's not). Is that possible ? Thx.

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• How do I boot Windows 8 into Safe Mode?

  - by Earlz

  I have Windows 8 Enterprise x64. It's installed a virtual machine. After trying to update VMWare's guest extension it black screened. After resetting it, now the virtual machine won't boot. It just says "automatic repair couldn't repair your PC" Everything I do ends with an error or it coming back to this screen. If I go to Troubleshoot Advanced Options Start up settings and then go to Safe Mode, all it will do is say "preparing automatic repair" and then "diagnosing your PC" and then will come straight back to the "automatic repair couldn't repair your PC" screen. It's as if it doesn't even attempt to go into safe made. Is there anything else I can do before I reformat?

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• C++ thread safety - exchange data between worker and controller

  - by peterchen

  I still feel a bit unsafe about the topic and hope you folks can help me - For passing data (configuration or results) between a worker thread polling something and a controlling thread interested in the most recent data, I've ended up using more or less the following pattern repeatedly: Mutex m; tData * stage; // temporary, accessed concurrently // send data, gives up ownership, receives old stage if any tData * Send(tData * newData) { ScopedLock lock(m); swap(newData, stage); return newData; } // receiving thread fetches latest data here tData * Fetch(tData * prev) { ScopedLock lock(m); if (stage != 0) { // ... release prev prev = stage; stage = 0; } return prev; // now current } Note: This is not supposed to be a full producer-consumer queue, only the msot recent data is relevant. Also, I've skimmed ressource management somewhat here. When necessary I'm using two such stages: one to send config changes to the worker, and for sending back results. Now, my questions assuming that ScopedLock implements a full memory barrier: do stage and/or workerData need to be volatile? is volatile necessary for tData members? can I use smart pointers instead of the raw pointers - say boost::shared_ptr? Anything else that can go wrong? I am basically trying to avoid "volatile infection" spreading into tData, and minimize lock contention (a lock free implementation seems possible, too). However, I'm not sure if this is the easiest solution. ScopedLock acts as a full memory barrier. Since all this is more or less platform dependent, let's say Visual C++ x86 or x64, though differences/notes for other platforms are welcome, too. (a prelimenary "thanks but" for recommending libraries such as Intel TBB - I am trying to understand the platform issues here)

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