condition-variable

From the Wikipedia article on Polling Polling, or polled operation, in computer science, refers to actively sampling the status of an external device by a client program as a synchronous activity. Polling is most often used in terms of input/output (I/O), and is also referred to as polled I/O or software driven I/O. Polling is sometimes used synonymously with busy-wait polling (busy waiting). In this situation, when an I/O operation is required the computer does nothing other than check the status of the I/O device until it is ready, at which point the device is accessed. In other words the

First a little context : I'm in the process of learning about threading in C++11 and for this purpose, I'm trying to build a small actor class, essentially (I left the exception handling and propagation stuff out) like so: class actor { private: std::atomic<bool> stop; private: std::condition_variable interrupt; private: std::thread actor_thread; private: message_queue incoming_msgs; public: actor() : stop(false), actor_thread([&]{ run_actor(); }) {} public: virtual ~actor() { // if the actor is destroyed, we must ensure the thread dies too stop = true; // to this end, we have to interrupt the

What are the principles of a condition variable in synchronization of the processes of operating systems? Alexander Sandler Well, conditional variables allow you to wait for certain condition to occur. In practice your thread may sleep on conditional variable and other thread wakes it up. Conditional variable also usually comes with mutex. This allows you to solve following synchronisation problem: how can you check state of some mutex protected data structure and then wait until it's state changes to something else. I.e. /* in thread 1 */ pthread_mutex_lock(mx); /* protecting state access */

I'm trying to learn about condition variables and how to use it in a producer-consumer situation. I have a queue where one thread pushes numbers into the queue while another thread popping numbers from the queue. I want to use the condition variable to signal the consuming thread when there is some data placed by the producing thread. The problem is there are times (or most times) that it only pushes up to two items into the queue then hangs. I have indicated in the produce() function where it stops when running in debug mode. Can anyone help me point out why this is happening? I have the

I'm sure mutex isn't enough that's the reason the concept of condition variables exist; but it beats me and I'm not able to convince myself with a concrete scenario when a condition variable is essential. Differences between Conditional variables, Mutexes and Locks question's accepted answer says that a condition variable is a lock with a "signaling" mechanism. It is used when threads need to wait for a resource to become available. A thread can "wait" on a CV and then the resource producer can "signal" the variable, in which case the threads who wait for the CV get notified and can continue