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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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  • C# thread safety for class instances

    - by Steveng
    I am learning C# and I am confused with the thread safety of the copies of the class instances as below: eg: classA objA; classA objB = objA; objA.field1 = value2; //do I need lock around modification of field1? //let say we pass the objB to another thread objB.field1 = value1 //do I need a lock for objB because of the modification of field1? I am confused because coming from the background of C++, the class in C# is the reference type. If both objA and objB refer to the same memory underlying, then I would need a lock to protect the simultaneous writing to the field1. Could someone confirm with this or am I missing something? Thanks.

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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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  • 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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  • std::thread and class constructor and destructor

    - by toeplitz
    When testing threads in C++11 I have created the following example: #include <iostream> #include <thread> class Foo { public: Foo(void) { std::cout << "Constructor called: " << this << std::endl; } ~Foo(void) { std::cout << "Destructor called: " << this << std::endl; } void operator()() const { std::cout << "Operatior called: " << this << std::endl; } }; void test_normal(void) { std::cout << "====> Standard example:" << std::endl; Foo f; } void test_thread(void) { std::cout << "====> Thread example:" << std::endl; Foo f; std::thread t(f); t.detach(); } int main(int argc, char **argv) { test_normal(); test_thread(); for(;;); } Which prints the following: Why is the destructor called 6 times for the thread? And why does the thread report different memory locations?

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  • Is it thread safe to read a form controls value (but not change it) without using Invoke/BeginInvoke from another thread

    - by goku_da_master
    I know you can read a gui control from a worker thread without using Invoke/BeginInvoke because my app is doing it now. The cross thread exception error is not being thrown and my System.Timers.Timer thread is able to read gui control values just fine (unlike this guy: can a worker thread read a control in the GUI?) Question 1: Given the cardinal rule of threads, should I be using Invoke/BeginInvoke to read form control values? And does this make it more thread-safe? The background to this question stems from a problem my app is having. It seems to randomly corrupt form controls another thread is referencing. (see question 2) Question 2: I have a second thread that needs to update form control values so I Invoke/BeginInvoke to update those values. Well this same thread needs a reference to those controls so it can update them. It holds a list of these controls (say DataGridViewRow objects). Sometimes (not always), the DataGridViewRow reference gets "corrupt". What I mean by corrupt, is the reference is still valid, but some of the DataGridViewRow properties are null (ex: row.Cells). Is this caused by question 1 or can you give me any tips on why this might be happening? Here's some code (the last line has the problem): public partial class MyForm : Form { void Timer_Elapsed(object sender) { // we're on a new thread (this function gets called every few seconds) UpdateUiHelper updateUiHelper = new UpdateUiHelper(this); foreach (DataGridViewRow row in dataGridView1.Rows) { object[] values = GetValuesFromDb(); updateUiHelper.UpdateRowValues(row, values[0]); } // .. do other work here updateUiHelper.UpdateUi(); } } public class UpdateUiHelper { private readonly Form _form; private Dictionary<DataGridViewRow, object> _rows; private delegate void RowDelegate(DataGridViewRow row); private readonly object _lockObject = new object(); public UpdateUiHelper(Form form) { _form = form; _rows = new Dictionary<DataGridViewRow, object>(); } public void UpdateRowValues(DataGridViewRow row, object value) { if (_rows.ContainsKey(row)) _rows[row] = value; else { lock (_lockObject) { _rows.Add(row, value); } } } public void UpdateUi() { foreach (DataGridViewRow row in _rows.Keys) { SetRowValueThreadSafe(row); } } private void SetRowValueThreadSafe(DataGridViewRow row) { if (_form.InvokeRequired) { _form.Invoke(new RowDelegate(SetRowValueThreadSafe), new object[] { row }); return; } // now we're on the UI thread object newValue = _rows[row]; row.Cells[0].Value = newValue; // randomly errors here with NullReferenceException, but row is never null! }

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  • Threading in java vs C#

    - by ffayyaz
    I need a little confirmation over something i am confused at . I know how threads work in java. new DialList(string a , string b).start(); // where DialList is a class public class DialList extends Thread { public DialList(String a, string b) { FilePath = a; ThreadLogFile = b"; } public void run() { // some code to run in different thread } } Now i want to run same code in C# , Shall i put the code which is in run() into a method and do something like Thread t = new Thread (runcsharp); // Kick off a new thread t.Start(); static void runcsharp() { // code } or is there some other way to do it ?

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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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  • 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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  • IS ResultSet thread safe

    - by javatraniee
    Is ResultSet Thread safe? My question arises because in this i have used a different statement for each query i have delsared a ResultSet as an local variable but it gives me a error of Operation not allowed after ResultSet is closed. But my statements are working as i'm using the statements in insert and delete query.I have commented the ResultSet part and have not got the error !! The source code of my program can be referd to , in my earlier Question .

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  • Error with `Thread.Sleep` during automatic testing on TeamCity 5

    - by yeyeyerman
    Hello, I'm having some problems executing the tests of the application I'm developing. All the tests execute normally with ReSharper and in NCover. However, the execution of one of these tests in TeamCity is generating an error. This test initializes two objects, the object under test and a simulator of a real object. Both objects will communicate throug a serial link in a representation of the real scenario. ObjectSimulator r_simulator = new ObjectSimulator(...); ObjectDriver r_driver = new ObjectDriver(...); Assert.IsTrue(r_driver.Connect() == ErrorCode.Success); The simulator just do the following in the constructor public class ObjectSimulator { ... public ObjectSimulator() { // serial port configuration m_port = new SerialPort(); m_port.DataReceived += DataReceivedEvent; } ... } The main object has two threads. The main thread of the application and a timer to refresh a watchdog timer in the real object. public ErrorCode Connect() { ... StartSynchroTimer(); Thread.Sleep(4); // to check if the timer is working properly ... } The problem seems to be comming from the Thread.Sleep() call, as when I remove it everything works. The ObjectSimulator somehow doesn't execute the DataReceived event callback. How can I resolve this issue?

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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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  • 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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  • 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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  • pthread_exit return value

    - by Manty
    This is surprising for me. void * thread_func(void *arg) { pthread_exit(&ret); } int main(void) { pthread_t thr; int *exit_status; pthread_create(&thr, NULL, thread_func, NULL); sleep(2); pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); ret = 20; pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); return 0; } The output is value of exit status - 50 value of exit status - 20 I was expecting both the times the exit_status would be the actual exit value(50 in my case) of the thread. Instead it is just returning the value of the global variable which I used for pthread_exit. Is it not a bug?

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  • How to have a run in an Service?

    - by user1497664
    I have implemented an service that runs in a seperate process. This service contains a separate thread where i have a socket connection. This thread has a run() where it is continuously sending data to the port. My problem is after triggering the run() in the thread i don't get any contact with it anymore, i can see in the program that have open the socket that it consciously sends the data but the idea was that i while it is running i could change data that it sends for an example time. here is my run in the external thread: public void run() { if(run) { // Team and player names message is sent when entering in a game setBaseMessage(); SendMessageToCOMPort(base_message + CalculateCRC(base_message)); sleep(); // waits for 100 ms } } Anyone have any idea what might be wrong ?

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  • Thread-safe get (accessor method)

    - by sonofdelphi
    I'm currently using the following code for thread-safe access of a variable. int gnVariable; void getVariableValue(int *pnValue) { acquireLock(); //Acquires the protection mechanism *pnValue = gnVariable; releaseLock(); //Releasing the protection mechanism } I would like to change my API signature to a more user-friendly int getVariableValue(void); How should I rewrite the function - such that the users of the API don't have to bother about the locking/unlocking details?

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  • How to use CriticalSection - MFC?

    - by mapples
    I' am working on a small example and am a bit of curious using criticalsection in my example. What I'am doing is,I have a CStringArray(which has 10 elements added to it).I want to copy these 10 elements(string) to another CStringArray(am doing this to understand threading and Critical section),I have created 2 threads,Thread1 will copy the first 5 element to another CStringArray and Thread2 will copy the rest.Here two CStringArray are being used,I know only 1 thread can access it at a time.I wanted to know how this can be solved by using criticalsection or any other method. void CThreadingEx4Dlg::OnBnClickedOk() { // TODO: Add your control notification handler code here thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,this); thread2 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction2,this); } UINT MyThreadFunction1(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyFunction(0,5); return 0; } UINT MyThreadFunction2(LPARAM lparam) { CThreadingEx4Dlg* pthis = (CThreadingEx4Dlg*)lparam; pthis->MyFunction(6,10); return 0; } void CThreadingEx4Dlg::MyFunction(int minCount,int maxCount) { for(int i=minCount;i<=maxCount;i++) { CString temp; temp = myArray.GetAt(i); myShiftArray.Add(temp); } }

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  • c# run process without freezing my App's GUI

    - by Data-Base
    Hello, I want to start a process (calling another program), currently the external program takes time (it is normal)! but it freezes my GUI I saw allot of examples and I'm learning, it is hard to figure it out, trying to read and learn threading, but it is not that easy (at least for me) and good simple tutorial or code sample? cheers

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