How does the system handle new tasks when all worker threads in the thread pool are busy and the task queue is full?

If all worker threads in the pool are busy and the task queue is full, when attempting to add a new task, the system typically applies a failure handling policy, which depends on the thread pool implementation.

In C# (for example, when using ThreadPool), the task queue usually does not have a strict limit, but if the queue were full, the following options might occur:

• Waiting: the calling thread may block until space becomes available in the queue.
• Task rejection: the new task may be rejected with an error or ignored.
• Failure handler invocation: a handler can be configured to perform alternative actions.

Thus, the system cannot immediately process the new task, and the behavior depends on the pool settings and overload handling policy. It is important to design the system to avoid such situations, for example, by increasing the pool size or optimizing task processing.