function myobj(){ var gup=this; this.lastindex=-1; this.criticalSectionInTimer=0; this.updateTimer; this.start = function(l){ if((typeof this.updateTimer)=="number"){ clearInterval ( this.updateTimer ); } this.updateTimer=setInterval(function() {gup.getMessages();} , 30); } this.stop= functio...
Is semaphore an IPC mechanism? ...
Hi everyone: This is my first attempt on semaphores and threads. I constructed this code from examples and the man pages found on the Net. I have two doubts with this code. Why do I get a Bus error whenever I try semctl( I know this is the root of the problem because of the debug line 3 does not get printed) and how to prevent it? Wh...
I am using following code to limit use of resources. Once in a while(after 3-4 days of successful run) I get queue empty exception or the returned object is found to be null. I am wondering if I am limiting only 5 threads to enter this Get method, how come this happens. The places where GetConnection is called, ReleaseConnection is al...
I'm experiencing a lot of difficulty getting Semaphores to work on a Linux based system in C. The process of my application is such: Application starts Application forks into child/parent Each process uses sem_open with a common name to open the semaphore. If I create the semaphore before forking, it works fine. However, requiremen...
I have been studying internals of Java for quite some time. I am curious to learn and understand how threading/locking takes place in Java. So, in order to access a synchronized method or a synchronized block, the thread has to acquire the lock on the object first. So, now, here is what I need a bit more light. So, whenever the thread...
Hi, This is the reader-writer problem for just read consistency. Here is the algorithm, void reader() { while (1){ P(mutex); rc++; if (rc == 1) P(db); /* <---- A */ V(mutex); /* <---- B */ read_data_base(); P(mutex): rc--; V(mutex); if (rc ==0) V(db); } ...
I've heard these words related to concurrent programming, but what's the difference between them? ...
Throughout the resources I've read about multithreading, mutex is more often used and discussed compared to a semaphore. My question is when do you use a semaphore over a mutex? I don't see semaphores in Boost thread. Does that mean semaphores no longer used much these days? As far as I've understand, semaphores allow a resource to be s...
(In short: main()'s WaitForSingleObject hangs in the program below). I'm trying to write a piece of code that dispatches threads and waits for them to finish before it resumes. Instead of creating the threads every time, which is costly, I put them to sleep. The main thread creates X threads in CREATE_SUSPENDED state. The synch is done...
I have multiple threads that share use of a semaphore. Thread A holds the semaphore (using lock) and threads B and C are waiting on that same semaphore (also using lock). The threads share global variables, etc. Is there a technique in C# that I can use to shut down thread B? I can set a flag in A and have thread B check that flag and...
Ferryboats go back and forth, carrying passengers from one side of the canal to the other. Each boat can hold at most C passengers. The passengers wait for the boats to ferry them across the canal. A boat can start crossing the river only when it is full. A boat cannot start loading passengers on one side of the canal if another boat is ...
I have a Semaphore that runs trough a list of Job objects. Here is a sample of the code: List<Job> jobList = jobQueue.GetJobsWithStatus(status); if (jobList.Count > 0) { foreach (Job job in jobList) { semaphore.WaitOne(); // Only N threads can get here at once job.semaphore = semaphore; ThreadStart threadStart = ne...
JI have written a .NET C# Windows Form app in Visual Studio 2008 that uses a Semaphore to run multiple jobs as threads when the Start button is pressed. It’s experiencing an issue where the Form goes into a comma after being run for 40 minutes or more. The log files indicate that the current jobs complete, it picks a new job from the li...
I am trying to create a Win32 Semaphore object which is inheritable. This means that any child processes I launch may automatically have the right to act on the same Win32 object. My code currently looks as follows: Semaphore semaphore = new Semaphore(0, 10); Process process = Process.Start(pathToExecutable, arguments); But the sem...
I have a queue structure that is being used by several pthreads. The threads are supposed to dequeue from the queue if it's not empty and then do their business. I initially had this set up as a while loop where the threads checked whether the queue was empty using a mutex_lock. Unfortunately this slowed my program down to a crawl. I t...
The documentation for the .NET Semaphore class states that: There is no guaranteed order, such as FIFO or LIFO, in which blocked threads enter the semaphore. In this case, if I want a guaranteed order (either FIFO or LIFO), what are my options? Is this something that just isn't easily possible? Would I have to write my own Semaph...
Hi In previous question of mine, someone had meantioned that using Semaphores were expensive in C# compared to using a monitor. So I ask this, how can I replace the semaphore in this code with a monitor? I need function1 to return its value after function2 (in a separate thread) has been completed. I had replaced the Semaphore.WaitOne ...
You know we can use message queues with the function mq_receive(); what is a good way to implement that functionality (you know, waiting until the shared data is changed) with semaphores? ...
Hallo i need to install and libs for c.I am using a linux ubuntu o/s.Does anybody knows how i can install them? ...