C# – Is a bool read/write atomic in C#

.netbooleanc++concurrencylocking

Is accessing a bool field atomic in C#? In particular, do I need to put a lock around:

class Foo
{
   private bool _bar;

   //... in some function on any thread (or many threads)
   _bar = true;

   //... same for a read
   if (_bar) { ... }
}

Best Solution

Yes.

Reads and writes of the following data types are atomic: bool, char, byte, sbyte, short, ushort, uint, int, float, and reference types.

as found in C# Language Spec.

Edit: It's probably also worthwhile understanding the volatile keyword.

Related Solutions

C# – Find a private field with Reflection

Use BindingFlags.NonPublic and BindingFlags.Instance flags

FieldInfo[] fields = myType.GetFields(
                         BindingFlags.NonPublic | 
                         BindingFlags.Instance);

Java ReentrantReadWriteLocks – how to safely acquire write lock

I have made a little progress on this. By declaring the lock variable explicitly as a ReentrantReadWriteLock instead of simply a ReadWriteLock (less than ideal, but probably a necessary evil in this case) I can call the getReadHoldCount() method. This lets me obtain the number of holds for the current thread, and thus I can release the readlock this many times (and reacquire it the same number afterwards). So this works, as shown by a quick-and-dirty test:

final int holdCount = lock.getReadHoldCount();
for (int i = 0; i < holdCount; i++) {
   lock.readLock().unlock();
}
lock.writeLock().lock();
try {
   // Perform modifications
} finally {
   // Downgrade by reacquiring read lock before releasing write lock
   for (int i = 0; i < holdCount; i++) {
      lock.readLock().lock();
   }
   lock.writeLock().unlock();
}

Still, is this going to be the best I can do? It doesn't feel very elegant, and I'm still hoping that there's a way to handle this in a less "manual" fashion.

Best Solution

Related Solutions

C# – Find a private field with Reflection

Java ReentrantReadWriteLocks – how to safely acquire write lock

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