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  • Threading in C#

    - by j-t-s
    Hi All Just looking for something ultra simple. I need to spawn a method off to a new thread. I don't care when or how it ends. Can somebody please help me with this? Thank you

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  • UITableViewController executes delate functions before network request finishes

    - by user1543132
    I'm having trouble trying to populate a UITableView with the results of a network request. It seems that my code is alright as it works perfectly when my network is speedy, however, when it's not, the function - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath- still executes, which results in a bad access error. I presume that this is because the array that the aforesaid function attempts to utilize has not been populated. This brings me to my question: Is there anyway that I can have the UITableView delegate methods delayed to avoid this? - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"AlbumsCell"; //UITableViewCell *basicCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath]; AlbumsCell *cell = (AlbumsCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (!cell) { **// Here is where the Thread 1: EXC_BAD_ACCESS (code=2 address=0x8)** cell = [[[AlbumsCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } Album *album = [_albums objectAtIndex:[indexPath row]]; [cell setAlbum:album]; return cell; }

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  • Locking individual elements in a static collection?

    - by user638474
    I have a static collection of objects that will be frequently updated from multiple threads. Is it possible to lock individual objects in a collection instead of locking the entire collection so that only threads trying to access the same object in the collection would get blocked instead of every thread? If there is a better way to update objects in a collection from multiple threads, I'm all ears.

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  • How to address thread-safety of service data used for maintaining static local variables in C++?

    - by sharptooth
    Consider the following scenario. We have a C++ function with a static local variable: void function() { static int variable = obtain(); //blahblablah } the function needs to be called from multiple threads concurrently, so we add a critical section to avoid concurrent access to the static local: void functionThreadSafe() { CriticalSectionLockClass lock( criticalSection ); static int variable = obtain(); //blahblablah } but will this be enough? I mean there's some magic that makes the variable being initialized no more than once. So there's some service data maintained by the runtime that indicates whether each static local has already been initialized. Will the critical section in the above code protect that service data as well? Is any extra protection required for this scenario?

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  • makecontext segfault?

    - by cdietschrun
    I am working on a homework assignment that will be due in the next semester. It requires us to implement our own context switching/thread library using the ucontext API. The professor provides code that does it, but before a thread returns, he manually does some work and calls an ISR that finds another thread to use and swapcontexts to it or if none are left, exits. The point of the assignment is to use the uc_link field of the context so that when it hits a return it takes care of the work. I've created a function (type void/void args) that just does the work the functions did before (clean up and then calls ISR). The professor said he wanted this. So all that's left is to do a makecontext somewhere along the way on the context in the uc_link field so that it runs my thread, right? Well, when I do makecontext on seemingly any combination of ucontext_t's and function, I get a segfault and gdb provides no help.. I can skip the makecontext and my program exist 'normally' when it hits a return in the threads I created because (presumably) the uc_link field is not properly setup (which is what I'm trying to do). I also can't find anything on why makecontext would segfault. Can anyone help? stack2.ss_sp = (void *)(malloc(STACKSIZE)); if(stack2.ss_sp == NULL){ printf("thread failed to get stack space\n"); exit(8); } stack2.ss_size = STACKSIZE; stack2.ss_flags = 0; if(getcontext(&main_context) == -1){ perror("getcontext in t_init, rtn_env"); exit(5); } //main_context.uc_stack = t_state[i].mystk; main_context.uc_stack = stack2; main_context.uc_link = 0; makecontext(&main_context, (void (*)(void))thread_rtn, 0); I've also tried just thread_rtn, &thread_rtn and other things. thread_rtn is declared as void thread_rtn(void). later, in each thread. run_env is of type ucontext_t: ... t_state[i].run_env.uc_link = &main_context;

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  • Thread toggling

    - by sid
    Hi all, In Ubuntu, I am running 2 'C' applications, When I press key up/down the applications are alternatively getting the events. What might be the problem/solution? Ex: I have 'A application' and 'B application', I launch 'A application' and press the key up/down its working fine. If I simultaneously launch 'B application' and focus is on 'B application' then pressing key up/down will toggle between 'A application' & 'B application' so 2 times I have to press the key to move on 'B application'(focus is on 'B application'). 'A application' and 'B application' are threads. Thanks in advance-opensid

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  • How to handle error on other thread?

    - by markattwood
    Hi, I'm trying to handle errors that have occurred on other threads the .NET CF program is like below: static void Main() { Thread t = new Thread(Start); t.Start(); ... } void Start() { ... Exception here } In my situation, putting try catch in the Start method is impossible. How can I handle it in the global code?

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  • In C# is there a thread scheduler for long running threads?

    - by LogicMagic
    Hi, Our scenario is a network scanner. It connects to a set of hosts and scans them in parallel for a while using low priority background threads. I want to be able to schedule lots of work but only have any given say ten or whatever number of hosts scanned in parallel. Even if I create my own threads, the many callbacks and other asynchronous goodness uses the ThreadPool and I end up running out of resources. I should look at MonoTorrent... If I use THE ThreadPool, can I limit my application to some number that will leave enough for the rest of the application to Run smoothly? Is there a threadpool that I can initialize to n long lived threads?

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  • What happens if you break out of a Lock() statement?

    - by cyclotis04
    I'm writing a program which listens to an incoming TcpClient and handles data when it arrives. The Listen() method is run on a separate thread within the component, so it needs to be threadsafe. If I break out of a do while loop while I'm within a lock() statement, will the lock be released? If not, how do I accomplish this? Thanks! (Any other advice on the subject of Asynchronous TCP Sockets is welcome as well.) private void Listen() { do { lock (_client) { if (!_client.Connected) break; lock (_stateLock) { if (!_listening) break; if (_client.GetStream().DataAvailable) HandleData(); } } Thread.Sleep(0); } while (true); }

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  • Java ThreadPool for multiple identical tasks

    - by tdimmig
    I have 1 thread who sole job is to grab DatagramPackets off of a socket and stick them in a buffer. Another thread works out of that buffer, processing the DatagramPackets. I'd like to have a pool of threads working out of that buffer. I had thought to use a fixed thread pool to do this. To do so, do I need to create the pool, then submit enough runnables for execution to fill it up? I had hoped for a way to say "this is the thread/runnable that I want you to execute, this is how many I want running, GO!". Is there such a method of doing this? Is something other than a fixed thread pool better suited?

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  • executorservice to read data from database in chuncks and run process on them

    - by TazMan
    I'm trying to write a process that would read data from a database and upload it onto a cloud datastore. How can I decide the partition strategy of the data? I want to query the table in chunks and process each chunk in 10 threads. Each thread basically will send the data to an individual node on a 10 node cluster on the cloud.. Where in the below multi threading code will the dataquery to extract and send 10 concurrent requests for uploading data to cloud would be? public class Caller { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < 10; i++) { Runnable worker = new DomainCDCProcessor(i); executor.execute(worker); } executor.shutdown(); while (!executor.isTerminated()) { } System.out.println("Finished all threads"); } }

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  • Corrupt output with an HttpModule

    - by clementi
    I have an HttpModule that looks at the query string for a parameter called "cmd" and executes one of a small set of predefined commands that display server stats in XML. For example, http://server01?cmd=globalstats. Now, on rare occasions, like once out of hundreds of times, I will get corrupt output like this: <!-- the stats start displaying fine... --> <stats> <ServerName>SERVER01</ServerName> <StackName>Search</StackName> <TotalRequests>945</TotalRequests> <!-- ...until something has gone awry and now we're getting the markup of the home page! --> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> ...the rest of the home page markup... (Remove the comments in the example above.) I'm not all that familiar with HttpModules and the IIS pipeline, but could this be a threading problem? Or, what else?

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  • Multi-threading does not work correctly using std::thread (C++ 11)

    - by user1364743
    I coded a small c++ program to try to understand how multi-threading works using std::thread. Here's the step of my program execution : Initialization of a 5x5 matrix of integers with a unique value '42' contained in the class 'Toto' (initialized in the main). I print the initialized 5x5 matrix. Declaration of std::vector of 5 threads. I attach all threads respectively with their task (threadTask method). Each thread will manipulate a std::vector<int> instance. I join all threads. I print the new state of my 5x5 matrix. Here's the output : 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 It should be : 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 0 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 Here's the code sample : #include <iostream> #include <vector> #include <thread> class Toto { public: /* ** Initialize a 5x5 matrix with the 42 value. */ void initData(void) { for (int y = 0; y < 5; y++) { std::vector<int> vec; for (int x = 0; x < 5; x++) { vec.push_back(42); } this->m_data.push_back(vec); } } /* ** Display the whole matrix. */ void printData(void) const { for (int y = 0; y < 5; y++) { for (int x = 0; x < 5; x++) { printf("%d ", this->m_data[y][x]); } printf("\n"); } printf("\n"); } /* ** Function attached to the thread (thread task). ** Replace the original '42' value by another one. */ void threadTask(std::vector<int> &list, int value) { for (int x = 0; x < 5; x++) { list[x] = value; } } /* ** Return the m_data instance propertie. */ std::vector<std::vector<int> > &getData(void) { return (this->m_data); } private: std::vector<std::vector<int> > m_data; }; int main(void) { Toto toto; toto.initData(); toto.printData(); //Display the original 5x5 matrix (first display). std::vector<std::thread> threadList(5); //Initialization of vector of 5 threads. for (int i = 0; i < 5; i++) { //Threads initializationss std::vector<int> vec = toto.getData()[i]; //Get each sub-vectors. threadList.at(i) = std::thread(&Toto::threadTask, toto, vec, i); //Each thread will be attached to a specific vector. } for (int j = 0; j < 5; j++) { threadList.at(j).join(); } toto.printData(); //Second display. getchar(); return (0); } However, in the method threadTask, if I print the variable list[x], the output is correct. I think I can't print the correct data in the main because the printData() call is in the main thread and the display in the threadTask function is correct because the method is executed in its own thread (not the main one). It's strange, it means that all threads created in a parent processes can't modified the data in this parent processes ? I think I forget something in my code. I'm really lost. Does anyone can help me, please ? Thank a lot in advance for your help.

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  • How to check if a thread is busy in C#?

    - by Sam
    I have a Windows Forms UI running on a thread, Thread1. I have another thread, Thread2, that gets tons of data via external events that needs to update the Windows UI. (It actually updates multiple UI threads.) I have a third thread, Thread3, that I use as a buffer thread between Thread1 and Thread2 so that Thread2 can continue to update other threads (via the same method). My buffer thread, Thread3, looks like this: public class ThreadBuffer { public ThreadBuffer(frmUI form, CustomArgs e) { form.Invoke((MethodInvoker)delegate { form.UpdateUI(e); }); } } What I would like to do is for my ThreadBuffer to check whether my form is currently busy doing previous updates. If it is, I'd like for it to wait until it frees up and then invoke the UpdateUI(e). I was thinking about either: a) //PseudoCode while(form==busy) { // Do nothing; } form.Invoke((MethodInvoker)delegate { form.UpdateUI(e); }); How would I check the form==busy? Also, I am not sure that this is a good approach. b) Create an event in form1 that will notify the ThreadBuffer that it is ready to process. // psuedocode List<CustomArgs> elist = new List<CustomArgs>(); public ThreadBuffer(frmUI form, CustomArgs e) { from.OnFreedUp += from_OnFreedUp(); elist.Add(e); } private form_OnFreedUp() { if (elist.count == 0) return; form.Invoke((MethodInvoker)delegate { form.UpdateUI(elist[0]); }); elist.Remove(elist[0]); } In this case, how would I write an event that will notify that the form is free? and c) an other ideas?

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  • Interrupt a thread in DatagramSocket.receive

    - by SEK
    I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses Socket.accept(), which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive, and doesn't exit that method. Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close()?

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  • Java: multi-threaded maps: how do the implementations compare?

    - by user346629
    I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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  • How to synchronize access to many objects

    - by vividos
    I have a thread pool with some threads (e.g. as many as number of cores) that work on many objects, say thousands of objects. Normally I would give each object a mutex to protect access to its internals, lock it when I'm doing work, then release it. When two threads would try to access the same object, one of the threads has to wait. Now I want to save some resources and be scalable, as there may be thousands of objects, and still only a hand full of threads. I'm thinking about a class design where the thread has some sort of mutex or lock object, and assigns the lock to the object when the object should be accessed. This would save resources, as I only have as much lock objects as I have threads. Now comes the programming part, where I want to transfer this design into code, but don't know quite where to start. I'm programming in C++ and want to use Boost classes where possible, but self written classes that handle these special requirements are ok. How would I implement this? My first idea was to have a boost::mutex object per thread, and each object has a boost::shared_ptr that initially is unset (or NULL). Now when I want to access the object, I lock it by creating a scoped_lock object and assign it to the shared_ptr. When the shared_ptr is already set, I wait on the present lock. This idea sounds like a heap full of race conditions, so I sort of abandoned it. Is there another way to accomplish this design? A completely different way?

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  • Does SetThreadPriority cause thread reschedulling?

    - by Suma
    Consider following situation, assuming single CPU system: thread A is running with a priority THREAD_PRIORITY_NORMAL, signals event E thread B with a priority THREAD_PRIORITY_LOWEST is waiting for an event E (Note: at this point the thread is not scheduled because it is runnable, but A is higher priority and runnable as well) thread A calls SetThreadPriority(B, THREAD_PRIORITY_ABOVE_NORMAL) Is thread B re-scheduled immediately to run, or is thread A allowed to continue until current time-slice is over, and B is scheduled only once a new time-slice has begun? I would be interested to know the answer for WinXP, Vista and Win7, if possible. Note: the scenario above is simplified from my real world code, where multiple threads are running on multiple cores, but the main object of the question stays: does SetThreadPriority cause thread scheduling to happen?

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  • Real World Examples of read-write in concurrent software

    - by Richard Fabian
    I'm looking for real world examples of needing read and write access to the same value in concurrent systems. In my opinion, many semaphores or locks are present because there's no known alternative (to the implementer,) but do you know of any patterns where mutexes seem to be a requirement? In a way I'm asking for candidates for the standard set of HARD problems for concurrent software in the real world.

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  • vs2002: c# multi threading question..

    - by dotnet-practitioner
    I would like to invoke heavy duty method dowork on a separate thread and kill it if its taking longer than 3 seconds. Is there any problem with the following code? class Class1 { /// <summary> /// The main entry point for the application. /// </summary> /// [STAThread] static void Main(string[] args) { Console.WriteLine("starting new thread"); Thread t = new Thread(new ThreadStart(dowork)); t.Start(); DateTime start = DateTime.Now; TimeSpan span = DateTime.Now.Subtract(start); bool wait = true; while (wait == true) { if (span.Seconds>3) { t.Abort(); wait = false; } span = DateTime.Now.Subtract(start); } Console.WriteLine("ending new thread after seconds = {0}", span.Seconds); Console.WriteLine("all done"); Console.ReadLine(); } static void dowork() { Console.WriteLine("doing heavy work inside hello"); Thread.Sleep(7000); Console.WriteLine("*** finished**** doing heavy work inside hello"); } }

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  • Waiting for a submitted job to finish in Oracle PL/SQL?

    - by vicjugador
    I'm looking for the equivalent of Java's thread.join() in PL/SQL. I.e. I want to kick off a number of jobs (threads), and then wait for them to finish. How is this possible in PL/SQL? I'm thinking of using dbms_job.submit (I know it's deprecated). dbms_scheduler is also an alternative. My code: DECLARE jobno1 number; jobno2 number; BEGIN dbms_job.submit(jobno1,'begin dbms_lock.sleep(10); dbms_output.put_line(''job 1 exit'');end;'); dbms_job.submit(jobno2,'begin dbms_lock.sleep(10); dbms_output.put_line(''job 2 exit'');end;'); dbms_job.run(jobno1); dbms_job.run(jobno2); //Need code to Wait for jobno1 to finish //Need code to Wait for jobno2 to finish END;

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  • Java: "implements Runnable" vs. "extends Thread"

    - by user65374
    From what time I've spent with threads in Java, I've found these two ways to write threads. public class ThreadA implements Runnable { public void run() { //Code } } //with a "new Thread(threadA).start()" call public class ThreadB extends Thread { public ThreadB() { super("ThreadB"); } public void run() { //Code } } //with a "threadB.start()" call Is there any significant difference in these two blocks of code?

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  • How do I make this Java code operate properly? [Multi-threaded, race condition]

    - by Fixee
    I got this code from a student, and it does not work properly because of a race condition involving x++ and x--. He added synchronized to the run() method trying to get rid of this bug, but obviously this only excludes threads from entering run() on the same object (which was never a problem in the first place) but doesn't prevent independent objects from updating the same static variable x at the same time. public class DataRace implements Runnable { static volatile int x; public synchronized void run() { for (int i = 0; i < 10000; i++) { x++; x--; } } public static void main(String[] args) throws Exception { Thread [] threads = new Thread[100]; for (int i = 0; i < threads.length; i++) threads[i] = new Thread(new DataRace()); for (int i = 0; i < threads.length; i++) threads[i].start(); for (int i = 0; i < threads.length; i++) threads[i].join(); System.out.println(x); // x not always 0! } } Since we cannot synchronize on x (because it is primitive), the best solution I can think of is to create a new static object like static String lock = ""; and enclose the x++ and x-- within a synchronized block, locking on lock. But this seems really awkward. Is there a better way?

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  • Can I overwrite an Object that has been Locked() in C#?

    - by makerofthings7
    I have a few objects that I'd like to send to the server, but I want to make sure that this is the only thread that moving the data from Stage to Upload. Is the following code valid in a multithreaded environment? List<CounterInternal> UploadToServer = new List<CounterInternal>(); List<CounterInternal> StagingQueue = new List<CounterInternal>(); lock (this.UploadToServer) lock (this.StagingQueue) { if (UploadToServer.Count == 0) { UploadToServer = StagingQueue.DoDeepCopyExtensionMethod(); // is the following line valid given that I have a Lock() on it? StagingQueue = new List<CounterInternal>(); } } }

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