volatile - small question

[Nick]

I am right in thinking that if I have a class that can be accessed by
more than one thread in my application then I should mark *all*
instance variables within that class with the volatile keyword.
Also is it right that if the access to the variable is within a lock
then this is not required, since all 'memory'/caches are up to date

Thanks in advance
Nick

 

[Willy Denoyette [MVP]]

I am right in thinking that if I have a class that can be accessed by
more than one thread in my application then I should mark *all*
instance variables within that class with the volatile keyword.
Also is it right that if the access to the variable is within a lock
then this is not required, since all 'memory'/caches are up to date

Thanks in advance
Nick

Use one of the synchronization primitives like Monitors, they have
acquire/release semantics. Use volatile only for special cases of
synchronization, f.i when you realy need to write thread-safe lock-free
code, IMO something which is very hard to be reliably done on the CLR.

Willy.

 

[Jon Skeet [C# MVP]]

I am right in thinking that if I have a class that can be accessed by
more than one thread in my application then I should mark *all*
instance variables within that class with the volatile keyword.

No. I find that volatile is very rarely the way to create thread-safe
classes.

Also is it right that if the access to the variable is within a lock
then this is not required, since all 'memory'/caches are up to date

Yes. Like Willy, I'd suggest using the synchronization primitives most
of the time.

See my article on threading at
http://www.pobox.com/~skeet/csharp/threads
for more details.