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  • Use Thread-local Storage to Reduce Synchronization

    Synchronization is often an expensive operation that can limit the performance of a multithreaded program. Using thread-local data structures instead of data structures shared by the threads can reduce synchronization in certain cases, allowing a program to run faster.

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  • CODESonCLOUD - Safe your Code on CLOUD

    - by user1277257
    A brand new system where you can keep your code snippets easily: CODES on CLOUD Now on, you can save your codes that you want to note down,which you encounter momently and you use frequently or the ones you say ‘ this may be useful’ on CODESonCLOUD, also, you can get through to your codes easily from anywhere you wish. Besides, you can share your codes with globally. Do not look for www.CODESonCLOUD.com

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  • [Java] - Problem having my main thread sleeping

    - by Chris
    I'm in a Java class and our assignment is to let us explore threads in Java. So far so good except for this one this one problem. And I believe that could be because of my lack of understanding how Java threads work at the moment. I have the main thread of execution which spawns new threads. In the main thread of execution in main() I am calling Thread.sleep(). When I do I get an Unhandled exception type InterruptedException. I am unsure of why I am getting this? I thought this was because I needed a reference to the main thread so I went ahead and made a reference to it via Thread.currentThread(). Is this not the way to have the thread sleep? What I need to do is have the main thread wait/sleep/delay till it does it required work again. Any help would be much appreciated.

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  • Thread Local Storage and local method variables

    - by miguel
    In c#, each thread has its own stack space. If this is the case, why is the following code not thread-safe? (It is stated that this code is thread-safe on this post: Locking in C# class Foo { private int count = 0; public void TrySomething() { count++; } } As count is an int (stack variable), surely this value would be isolated to an individual thread, on its own stack, and therefore thread-safe? I am probably missing something here, but I dont understand what is actually in Thread Local Storage if not stack-based variables for the thread?

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  • How do I refactor this IEnumerable<T> to be thread-safe?

    - by DayOne
    I am looking at Skeet's AtomicEnumerable but I'm not sure how to integrate it into my current IEnumerable exmaple below (http://msmvps.com/blogs/jon_skeet/archive/2009/10/23/iterating-atomically.aspx) Basically I want to foreach my blahs type in a thread-safe way. thanks public sealed class Blahs : IEnumerable<string> { private readonly IList<string> _data = new List<string>() { "blah1", "blah2", "blah3" }; public IEnumerator<string> GetEnumerator() { return _data.GetEnumerator(); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } }

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  • How to correctly stop thread which is using Control.Invoke

    - by codymanix
    I tried the following (pseudocode) but I always get a deadlock when Iam trying to stop my thread. The problem is that Join() waits for the thread to complete and a pending Invoke() operation is also waiting to complete. How can I solve this? Thread workerThread = new Thread(BackupThreadRunner); volatile bool cancel; // this is the thread worker routine void BackupThreadRunner() { while (!cancel) { DoStuff(); ReportProgress(); } } // main thread void ReportProgress() { if (InvokeRequired) { Invoke(ReportProgress); } UpdateStatusBarAndStuff(); } // main thread void DoCancel() { cancel=true; workerThread.Join(); }

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  • Java: serial thread confinement question

    - by denis
    Assume you have a Collection(ConcurrentLinkedQueue) of Runnables with mutable state. Thread A iterates over the Collection and hands the Runnables to an ExecutorService. The run() method changes the Runnables state. The Runnable has no internal synchronization. The above is a repetitive action and the worker threads need to see the changes made by previous iterations. So a Runnable gets processed by one worker thread after another, but is never accessed by more than one thread at a time - a case of serial thread confinement(i hope ;)). The question: Will it work just with the internal synchronization of the ConcurrentLinkedQueue/ExecutorSerivce? To be more precise: If Thread A hands Runnable R to worker thread B and B changes the state of R, and then A hands R to worker thread C..does C see the modifications done by B?

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  • Can the lock function be used to implement thread-safe enumeration?

    - by Daniel
    I'm working on a thread-safe collection that uses Dictionary as a backing store. In C# you can do the following: private IEnumerable<KeyValuePair<K, V>> Enumerate() { if (_synchronize) { lock (_locker) { foreach (var entry in _dict) yield return entry; } } else { foreach (var entry in _dict) yield return entry; } } The only way I've found to do this in F# is using Monitor, e.g.: let enumerate() = if synchronize then seq { System.Threading.Monitor.Enter(locker) try for entry in dict -> entry finally System.Threading.Monitor.Exit(locker) } else seq { for entry in dict -> entry } Can this be done using the lock function? Or, is there a better way to do this in general? I don't think returning a copy of the collection for iteration will work because I need absolute synchronization.

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  • c style thread creation in python

    - by chandank
    Hi I am new to python and want to create multiple threads in a loop something like (in C style) for (;i < 10; i++) thread[i]= pthread_create(&thread[i],&attr,func) I am not sure how to do the same in python? Basically I want have that thread[] variable as global will create all thread at once and then will start then in once. I have written a similar python program that does it but I think having it in above style will be better. def thread_create(thread_number): command_string = "Thread-" + "%d" %thread_number thread = myThread(thread_number, command_string) thread.start() # Start new Threads for i in range(5): thread_create(i)

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  • Is this a valid, lazy, thread-safe Singleton implementation for C#?

    - by Matthew
    I implemented a Singleton pattern like this: public sealed class MyClass { ... public static MyClass Instance { get { return SingletonHolder.instance; } } ... static class SingletonHolder { public static MyClass instance = new MyClass (); } } From Googling around for C# Singleton implementations, it doesn't seem like this is a common way to do things in C#. I found one similar implementation, but the SingletonHolder class wasn't static, and included an explicit (empty) static constructor. Is this a valid, lazy, thread-safe way to implement the Singleton pattern? Or is there something I'm missing?

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  • Java Thread Message Passing

    - by pkulak
    I'm writing an Android app. I have a main method, which creates and runs a new Thread using an anonymous inner Runnable class. The run() method, when it's done, calls a method on it's parent class (in the main thread) that calls notifyDataSetChanged() so that the main thread can redraw the new data. This is causing all kinds of trouble (ViewRoot$CalledFromWrongThreadException). The thing is, this method being called from the worker thread is on the class that's created in the UI thread. Shouldn't that be running on the UI thread? Or am I missing something? Here's some code about what I'm talking about: public class Mealfire extends Activity { @Override public void onCreate(Bundle icicle) { (new Thread() { public void run() { // Do a bunch of slow network stuff. update(); } }).start(); } private void update() { myAdapter.notifyDatasetChanged(); } }

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  • Turn based synchronization between threads

    - by Amarus
    I'm trying to find a way to synchronize multiple threads having the following conditions: * There are two types of threads: 1. A single "cyclic" thread executing an infinite loop to do cyclic calculations 2. Multiple short-lived threads not started by the main thread * The cyclic thread has a sleep duration between each cycle/loop iteration * The other threads are allowed execute during the inter-cycle sleep of the cyclic thread: - Any other thread that attempts to execute during an active cycle should be blocked - The cyclic thread will wait until all other threads that are already executing to be finished Here's a basic example of what I was thinking of doing: // Somewhere in the code: ManualResetEvent manualResetEvent = new ManualResetEvent(true); // Allow Externally call CountdownEvent countdownEvent = new CountdownEvent(1); // Can't AddCount a CountdownEvent with CurrentCount = 0 void ExternallyCalled() { manualResetEvent.WaitOne(); // Wait until CyclicCalculations is having its beauty sleep countdownEvent.AddCount(); // Notify CyclicCalculations that it should wait for this method call to finish before starting the next cycle Thread.Sleep(1000); // TODO: Replace with actual method logic countdownEvent.Signal(); // Notify CyclicCalculations that this call is finished } void CyclicCalculations() { while (!stopCyclicCalculations) { manualResetEvent.Reset(); // Block all incoming calls to ExternallyCalled from this point forward countdownEvent.Signal(); // Dirty workaround for the issue with AddCount and CurrentCount = 0 countdownEvent.Wait(); // Wait until all of the already executing calls to ExternallyCalled are finished countdownEvent.Reset(); // Reset the CountdownEvent for next cycle. Thread.Sleep(2000); // TODO: Replace with actual method logic manualResetEvent.Set(); // Unblock all threads executing ExternallyCalled Thread.Sleep(1000); // Inter-cycles delay } } Obviously, this doesn't work. There's no guarantee that there won't be any threads executing ExternallyCalled that are in between manualResetEvent.WaitOne(); and countdownEvent.AddCount(); at the time the main thread gets released by the CountdownEvent. I can't figure out a simple way of doing what I'm after, and almost everything that I've found after a lengthy search is related to producer/consumer synchronization which I can't apply here.

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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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  • Call an AsyncTask inside a Thread

    - by Arun
    I am working in an android application and I want to call an AsyncTask from my UI main thread. For that I want to call my AsyncTask from a thread. This is the method that I call from my main UI thread. This is working correctly CommonAysnk mobjCommonAysnk = new CommonAysnk(this, 1); mobjCommonAysnk.execute(); CommonAysnk is my AsyncTask class.I want to pass my activity and an integer parameter to the AsyncTask constructor. How can I call this from a thread as shown below method. Thread t = new Thread() { public void run() { try { CommonAysnk mobjCommonAysnk = new CommonAysnk(this, 1); mobjCommonAysnk.execute(); } catch (Exception ex) { }}}; t.start(); When I tried to call it from a Thread and I am not able to pass the activity parameter correctly. How can we sole this. Thanks

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  • External-Harddisk drive couldn't run unless in safe mode

    - by zfm
    This is the strangest thing ever happened to me... I have an external harddisk drive (ext-HDD), bought around 2 years ago (don't know whether this is an important issue or not). Here, I have a video file (.avi) in my internal harddisk dive (HDD), it worked very well, then I copy it to my ext-HDD, but I couldn't run the file directly from my ext-HDD! I tried to copy it back to my HDD (from the ext-HDD), and now the copy couldn't be run on my HDD too. Remember that I copy the file, so the original one was still there. I tried to go to safe mode (forget to mention, I use Windows 7 Pro), and this is where the strange thing happened, the copied files (both in ext-HDD and HDD) can be run in this safe mode. So, my question is, what could actually be happened there? PS: My ext-HDD is Axioo, 250 GB, exFAT... Edited: Currently I used MacOSX, and the file in the harddisk still can't be run. I haven't tried safe mode for Mac (is there one?), but will try later (if there is)

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  • C++ Simple thread with parameter (no .net)

    - by Marc Vollmer
    I've searched the internet for a while now and found different solutions but then all don't really work or are to complicated for my use. I used C++ until 2 years ago so it might be a bit rusty :D I'm currently writing a program that posts data to an URL. It only posts the data nothing else. For posting the data I use curl, but it blocks the main thread and while the first post is still running there will be a second post that should start. In the end there are about 5-6 post operations running at the same time. Now I want to push the posting with curl into another thread. One thread per post. The thread should get a string parameter with the content what to push. I'm currently stuck on this. Tried the WINAPI for windows but that crashes on reading the parameter. (the second thread is still running in my example while the main thread ended (waiting on system("pause")). It would be nice to have a multi plattform solution, because it will run under windows and linux! Heres my current code: #define CURL_STATICLIB #include <curl/curl.h> #include <curl/easy.h> #include <cstdlib> #include <iostream> #include <stdio.h> #include <stdlib.h> #include <string> #if defined(WIN32) #include <windows.h> #else //#include <pthread.h> #endif using namespace std; void post(string post) { // Function to post it to url CURL *curl; // curl object CURLcode res; // CURLcode object curl = curl_easy_init(); // init curl if(curl) { // is curl init curl_easy_setopt(curl, CURLOPT_URL, "http://10.8.27.101/api.aspx"); // set url string data = "api=" + post; // concat post data strings curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str()); // post data res = curl_easy_perform(curl); // execute curl_easy_cleanup(curl); // cleanup } else { cerr << "Failed to create curl handle!\n"; } } #if defined(WIN32) DWORD WINAPI thread(LPVOID data) { // WINAPI Thread string pData = *((string*)data); // convert LPVOID to string [THIS FAILES] post(pData); // post it with curl } #else // Linux version #endif void startThread(string data) { // FUnction to start the thread string pData = data; // some Test #if defined(WIN32) CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)thread, &pData, 0, NULL); // Start a Windows thread with winapi #else // Linux version #endif } int main(int argc, char *argv[]) { // The post data to send string postData = "test1234567890"; startThread(postData); // Start the thread system("PAUSE"); // Dont close the console window return EXIT_SUCCESS; } Has anyone a suggestion? Thanks for the help!

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  • Microsoft Enterprise Library Caching Application Block not thread safe?!

    - by AlanR
    Good aftenoon, I created a super simple console app to test out the Enterprise Library Caching Application Block, and the behavior is blaffling. I'm hoping I screwed something that's easy to fix in the setup. Have each item expire after 5 seconds for testing purposes. Basic setup -- "every second pick a number between 0 and 2. if the cache doesn't already have it, put it in there -- otherwise just grab it from the cache. Do this inside a LOCK statement to ensure thread safety. APP.CONFIG: <configuration> <configSections> <section name="cachingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Caching.Configuration.CacheManagerSettings, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> </configSections> <cachingConfiguration defaultCacheManager="Cache Manager"> <cacheManagers> <add expirationPollFrequencyInSeconds="1" maximumElementsInCacheBeforeScavenging="1000" numberToRemoveWhenScavenging="10" backingStoreName="Null Storage" type="Microsoft.Practices.EnterpriseLibrary.Caching.CacheManager, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Cache Manager" /> </cacheManagers> <backingStores> <add encryptionProviderName="" type="Microsoft.Practices.EnterpriseLibrary.Caching.BackingStoreImplementations.NullBackingStore, Microsoft.Practices.EnterpriseLibrary.Caching, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Null Storage" /> </backingStores> </cachingConfiguration> </configuration> C#: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.EnterpriseLibrary.Common; using Microsoft.Practices.EnterpriseLibrary.Caching; using Microsoft.Practices.EnterpriseLibrary.Caching.Expirations; namespace ConsoleApplication1 { class Program { public static ICacheManager cache = CacheFactory.GetCacheManager("Cache Manager"); static void Main(string[] args) { while (true) { System.Threading.Thread.Sleep(1000); // sleep for one second. var key = new Random().Next(3).ToString(); string value; lock (cache) { if (!cache.Contains(key)) { cache.Add(key, key, CacheItemPriority.Normal, null, new SlidingTime(TimeSpan.FromSeconds(5))); } value = (string)cache.GetData(key); } Console.WriteLine("{0} --> '{1}'", key, value); //if (null == value) throw new Exception(); } } } } OUPUT -- How can I prevent the cache to returning nulls? 2 --> '2' 1 --> '1' 2 --> '2' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 0 --> '0' 1 --> '1' 2 --> '' 0 --> '0' 2 --> '2' 0 --> '0' 1 --> '' 2 --> '2' 1 --> '1' Press any key to continue . . . Thanks in advance, -Alan.

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  • How to write a "thread safe" function in C ?

    - by Andrei Ciobanu
    Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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  • Why Rails.cache is not thread safe?

    - by Freewind
    I know Rails.cache is ActiveSupport::Cache::MemoryStore, and it is not thread safe. I don't understand, why rails use a thread-unsafe cache as its default? Why not use ActiveSupport::Cache::SynchronizedMemoryStore? In my opinion, in a web site, if a cache is not thread-safe, it almost useless, because the requests are not handled in ONE thread. Do you use Rails.cache in you webapp? And how do you use it?

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  • Are JSF 2.x ViewScoped Beans Thread Safe?

    - by Mark
    I've been googling for a couple hours on this issue to no eval. WELD docs and the CDI spec are pretty clear regarding thread safety of the scopes provided. For example: Application Scope - not safe Session Scope - not safe Request Scope - safe, always bound to a single thread Conversation Scope - safe (due to the WELD proxy serializing access from multiple request threads) I can't find anything on the View Scope defined by JSF 2.x. It is in roughly the same bucket as the Conversation Scope in that it is very possible for multiple requests to hit the scope concurrently despite it being bound to a single view / user. What I don't know is if the JSF implementation serializes access to the bean from multiple requests. Anyone have knowledge of the spec or of the Morraja/MyFaces implementations that could clear this up?

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  • gdb - thread log

    - by sthustfo
    Hi all, While I trying to debug a 'C' program with gdb, I always get the following continuously on the gdb console. [Thread 0xb7fe4b70 (LWP 30576) exited] [New Thread 0xb7fe4b70 (LWP 30577)] [Thread 0xb7fe4b70 (LWP 30577) exited] [New Thread 0xb7fe4b70 (LWP 30578)] [Thread 0xb7fe4b70 (LWP 30578) exited] Is there any reason why this is printed? And anyway to block this? note: the program makes use of timers. Is that a possible cause?

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  • How to catch exception in the main thread if the exception occurs in the secondary thread?

    - by Ashish Ashu
    How to catch exception in the main thread if the exception occurs in the secondary thread? The code snippet for the scenario is given below: private void button1_Click(object sender, EventArgs e) { try { Thread th1 = new Thread(new ThreadStart(Test)); th1.Start(); } catch (Exception) { } } void Test() { for (int i = 0; i < 100; i++) { Thread.Sleep(100); if (i == 2) throw new MyException(); } } }

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