Locking two methods and ensure that only on thread is calling one method

Question

In a class I've two methods:

Method1(): void
Method2(): void

This class can be accessed by multiple threads. How can I realise, if "thread1" call "Method1", that "thread2" is waiting in "Method2" or in "Method1". This logic should also work, if "thread2" is calling "Method2", that "thread1" is waiting in "Method1" or "Method2"

My idea is this:

private object _lock = new object();

void Method1() {
 lock(_lock){
  //TODO: do something
 }
}

void Method2() {
 lock(_lock){
  //TODO: do something
 }
}

Will this work?

Do you want to *know* if some other thread is waiting or do you want to ensure that only one thread can run either of the methods at any one given time? — Lasse V. Karlsen, Oct 12 '16 at 07:13
I want to ensure that only one thread can run either of the methods. — Marcel Lambacher, Oct 12 '16 at 07:41

score 1 · Accepted Answer · answered Oct 12 '16 at 08:09

Your code will work after your clarification in comments.

With the given code you will:

Ensure only one thread can execute either Method1 or Method2 at the same time
1. If one thread is inside Method1, other threads will wait if they try to call either Method1 or Method2.
If Method1 calls into Method2 or vice versa, this will also work as the same thread can lock the same object more than once.

In other words, this is not a deadlock:
```
lock (x)
    lock (x)
        ....
```

So your code should work just fine.

score 0 · Answer 2 · answered Oct 12 '16 at 07:18

0

You cant do on same object, You can use Monitor. Monitor allows re-entrancy

answered Oct 12 '16 at 07:18

Vivek Nuna

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So, with a "Monitor" I can ensure that only on thread can run either of the methods? – Marcel Lambacher Oct 12 '16 at 07:41
lock() is [syntactic sugar for Monitor](https://stackoverflow.com/a/6029829/13744), but with the Monitor.Exit code written out for you. – gbjbaanb Apr 07 '18 at 15:35

score 0 · Answer 3 · edited May 23 '17 at 10:27

0

You can use the WaitOne() function of an AutoResetEvent to allow only one function to access resources at a time, when it's finished called Set().

Example here: Synchronizing two threads with AutoResetEvent

MSDN Reference: https://msdn.microsoft.com/en-us/library/system.threading.autoresetevent(v=vs.110).aspx

edited May 23 '17 at 10:27

Community

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answered Oct 12 '16 at 07:40

Mark Rawson

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score 0 · Answer 4 · edited May 23 '17 at 12:18

0

Your methods should be Synchronized. See C# version of java's synchronized keyword? to get an idea on how to do it in c#.

edited May 23 '17 at 12:18

Community

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answered Oct 12 '16 at 07:40

AhmadWabbi

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score 0 · Answer 5 · answered Oct 12 '16 at 08:02

This will work. Since you're locking on the same object, only one lock { } block will be executed at a given time.

How can I realise, if "thread1" call "Method1", that "thread2" is waiting in "Method2" or in "Method1". This logic should also work, if "thread2" is calling "Method2", that "thread1" is waiting in "Method1" or "Method2"

The logic will work. But not sure what you're trying to ask here.

Locking two methods and ensure that only on thread is calling one method

5 Answers5