CODEWITHSUNDEEP
c#multithreadingthread-sleep
Lukas
Lukas

Reputation: 2352

Waking a thread in C#

I am looking for a simple way to put a thread to sleep and to wake it. The thread runs in background in an infinite loop and sometimes does some work, sometimes just runs through. I have found out that there is no corresponding Wait() to the Sleep() and waking a thread with Interrupt() causes an exception. Apparently a sleeping thread is not meant to be disturbed.
Since I know when the work appears it seems a good idea to tell the thread, instead of having it check over and over again.

How can a thread be put to a 'lighter sleep' to be able to wake up alone each second or at a command from other thread? 

//Thread to put to sleep and wake (thread1)
while (true)
{
    if (thereIsWork)
    { DoWork(); }
    //put thread to sleep in a way that other threads can wake it, and it wakes alone after some time (eg. 1000 ms)
    // Thread.Sleep(1000); //nice, but not working as desired
}

-

//Other thread:

thereIsWork = true;
//thread1.Wake(); //Not existing

Upvotes: 1

Views: 2022

Answers (4)

BlackCath
BlackCath

Reputation: 826

I'n not an expert with threads, but maybe EventWaitHandle is what you're looking for. Check this link

Upvotes: 0

Dave Hillier
Dave Hillier

Reputation: 19063

How about using a blocking queue, with Monitor Pulse and Wait:

class BlockingQueue<T>
{
    private Queue<T> _queue = new Queue<T>();
    public void Enqueue(T data)
    {
        if (data == null) throw new ArgumentNullException("data");
        lock (_queue)
        {
            _queue.Enqueue(data);
            Monitor.Pulse(_queue);
        }
    }
    public T Dequeue()
    {
        lock (_queue)
        {
            while (_queue.Count == 0) Monitor.Wait(_queue);
            return _queue.Dequeue();
        }
    }
}

Then thread 1 becomes

BlockingQueue<Action> _workQueue = new BlockingQueue<Action>();

while (true)
{
    var workItem = _workQueue.Dequeue();
    workItem();
}

And the other thread:

_workQueue.Enqueue(DoWork);

NB: you should probably use the built in type if you're using .Net 4 BlockingCollection using Add and Take instead of Enqueue and Dequeue.

Edit: Ok. If you want it really simple...

//Thread to put to sleep and wake (thread1)
while (true)
{
    lock(_lock)
    {
        while (!thereIsWork) Monitor.Wait(_lock);
        DoWork(); 
    }
    //put thread to sleep in a way that other threads can wake it, and it wakes alone after some time (eg. 1000 ms)
    // Thread.Sleep(1000); //nice, but not working as desired
}

and

//Other thread:
lock(_lock)
{
    thereIsWork = true;
    //thread1.Wake(); //Not existing
    Monitor.Pulse(_lock);
}

Upvotes: 1

BrokenGlass
BrokenGlass

Reputation: 160892

You can use an AutoResetEvent for this - just call Set() to signal work needs to be done and have your thread wait for it to be called using WaitOne().

This means the threads that are communicating this way share the same AutoResetEvent instance - you can pass it in as a dependency for the thread that does the actual work.

Upvotes: 4

Neil Barnwell
Neil Barnwell

Reputation: 42125

The thread shouldn't Sleep(), it should call WaitOne() on an AutoResetEvent or ManualResetEvent until some other thread calls Set() on that same resetevent object.

Upvotes: 4

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