Programming .NET Components, 2nd Edition

Synchronizing Threads

For all its advantages, introducing multithreading into your application opens up a Pandora’s box of synchronization and concurrency-management issues. With multithreading, you have to worry about threads deadlocking themselves while contesting for the same resources, you must take steps to synchronize access to objects by concurrent multiple threads, and you need to be prepared to handle method reentrancy.

When it comes to programming components that are likely to be used by you or by others in multithreaded applications, you must ensure they are thread-safe . A thread-safe component is one that is equipped with mechanisms to prevent multiple threads from simultaneously accessing its methods and corrupting its state. Imagine, for example, a linked list component that provides methods for adding and removing elements from a list. When the component adds or removes an element, the component keeps the list in a temporarily inconsistent state, while node references are updated and written to reflect the change. If a client asks to add an element to the list on one thread (T1), and that thread is preempted by another thread (T2) during the request, T1 can leave the list in an inconsistent state, and T2 can crash trying to access the list. To make the list thread-safe, you should make sure that only one thread can access it at a time and that all other threads are barred until the current thread has finished.

With multithreaded applications, you must also concern ...