Thread Life Cycle and States

Thread Life Cycle & States

• A thread can be in different states throughout its execution.

Unstarted

• A newly created thread in the Common Language Runtime (CLR) is in the Unstarted state and does not begin executing immediately.

Started (Ready or Runnable)

• The thread transitions to the Started state (also referred to as Ready or Runnable) when the Start method is invoked.

Running

• The highest priority Started thread enters the Running state and is actively executing.

Stopped

• A Running thread enters the Stopped state when its job or task is completed.

Aborted

• A Running thread can be forcefully terminated by calling the Abort method. This throws a ThreadAbortException, which, if caught, is automatically rethrown at the end of the catch block.

Blocked

• A Running thread enters the Blocked state when it initiates an input/output (I/O) request. The CPU time is not allocated to a Blocked thread while it performs I/O operations.

WaitSleepJoin

• A Running thread can enter the WaitSleepJoin state:
  • By invoking the Sleep method to pause for a specified duration
  • By invoking the Monitor.Wait method for synchronization.

Resuming from WaitSleepJoin

• A thread can resume from the WaitSleepJoin state:
  • When the sleep duration in the Sleep method expires.
  • When another thread calls the Monitor.Pulse method to move the next waiting thread back to the Started state.
  • When another thread calls the Monitor.PulseAll method to move all waiting threads back to the Started state.
  • When another thread calls the waiting thread's Interrupt method.

Joining Threads

• If a thread's execution depends on the completion of another thread, it can call that thread's Join method. This causes the waiting thread to remain in the WaitSleepJoin state until the joined thread finishes executing.

Thread Properties

• The Thread class provides several properties:
  • CurrentThread: Returns the current thread executing.
  • IsAlive: Indicates whether the thread is currently running.
  • IsBackground: Indicates whether the thread is a background thread.
  • Name: Gets or sets the thread's name.
  • Priority: Gets or sets the thread's priority.
  • ThreadState: Gets the thread's current state.

Sample Code Example

• The code demonstrates:
  • Creating and starting a child thread using ThreadStart and Thread.
  • Accessing the Thread.CurrentThread property to identify the main thread.
  • Utilizing the Thread.Sleep method to pause execution.
  • Handling the ThreadAbortException in a catch block.
  • Illustrating the finally block for cleanup tasks.

Managing Thread Execution

• Employ Thread methods for controlling thread execution:
  • Start: Begin execution.
  • Abort: Stop execution forcefully.
  • Join: Wait for a thread to complete.
  • Sleep: Suspend execution for a specified duration.
  • Interrupt: Interrupt a waiting thread.

Practical Implications

• The provided code illustrates practical aspects of multithreading in .NET applications, focusing on how to create, manipulate, and monitor threads. It demonstrates fundamental concepts like creating child threads, controlling their execution, and dealing with exceptions.

Explore the different states a thread can enter during its lifecycle in the Common Language Runtime (CLR). From Unstarted to Running, and how threads can transition to Stopped or Aborted states, this quiz will enhance your understanding of thread management and execution flow.