C# Thread synchronization
- 2. THREAD a single flow of execution logic in a program. Enable your program to perform concurrent processing. Increases efficiency and responsiveness. Share resources. Unpredictable execution order.
- 3. SYECHROIZATION Simultaneous access to shared resource can cause inconsistent and incorrect output. Introduce resource-sharing issues such as deadlocks and race conditions So, the need of synchronized access to the shared resources. System. Threading namespace.
- 4. PROBLEM Two threads updating a single shared variable One thread wants to decrement amount by 10K The other thread wants to decrement amount by 50% amount= 100000; … … amount = 0.50 * amount; … … … … amount= amount - 10000; … …
- 6. (CASE 1) … r1 = load from amount r1 = r1 - 10000; store r1 to amount … … r1 = load from amount r1 = 0.5 * r1 store r1 to amount … amount= 100000; amount= ?
- 7. (CASE 2) … r1 = load from amount r1 = r1 - 10000; store r1 to amount … … r1 = load from amount r1 = 0.5 * r1 store r1 to amount … amount= 100000; amount= ?
- 8. (CASE 3) … r1 = load from amount r1 = r1 - 10000; store r1 to amount … … r2 = load from amount r2 = 0.5 * r2 store r2 to amount … amount= 100000; amount= ?
- 9. SOLUTION 1. Lock 2. Monitor 3. Mutex 4. Semaphore
- 10. LOCK The lock allows us to define a scope of code that must be synchronized between threads so that incoming threads cannot interrupt the current thread. Syntax- … lock(ThreadLock) { // Critical Section } ….
- 11. MONITOR The lock is just a shorthand notation for working with the System.Threading.Monitor class. Syntax- Monitor.Enter(threadLock); … //Critical Section … Monitor.Exit(threadLock);
- 12. WHY MONITOR ??? If we use the Monitor, we're able to tell the active thread to wait by using Wait() method and let the waiting threads know when the current thread is completed via Pulse() and PulseAll() methods.
- 13. MUTEX A Mutex is similar to the lock, however, it can work across multiple processes. But it is slower than the lock. Mutex allows us to call the WaitOne() method to lock and ReleaseMutex() to unlock. a Mutex can be released only from the same thread which obtained it. The primary use for a cross-process Mutex is to ensure that only one instance of a program can run at a time
- 14. MUTEX Syntax- static Mutex mutex = new Mutex(); Mutex.waitone() ….. ….. Mutex.ReleaseMutex();
- 15. SEMAPHORE A Semaphore with a capacity of one is like a Mutex or lock. However, the Semaphore has no owner. We can use Semaphores to limit concurrency by preventing too many threads from executing a particular piece of code at once. Syntax- // 4 available from capacity of 5 static Semaphore semaphore = new Semaphore(4,5); … semaphore.WaitOne(); //critical section semaphore.Release(); …