Thread Locking In Static Methods - How?

[McFly Racing]

Thread Locking In Static Methods



I have the need for a Log Manger class that has static methods. Normally I
would use the lock statement or a Monitor statement both of which take a
reference to (this). In the case of these static methods I am not able to
do that.



How should I perform thread locking within static methods like this? Thank
you.

 

[ShaneB]

public static void LogText(string text)
{
lock (typeof(ThisClassType))
{
...
}
}

ShaneB

 

[McFly Racing]

If I do it this way it seems like I will be loking the whole class instead
of just this method, is that correct? Thank you.

 

[John M Deal]

No. What this does is cause a lock of any code location that uses the
same lock definition. If every method in the class had its code
encompassed by the same statement it would cause the whole class to lock
anytime one of the methods was entered, but only if that was the case.

If you want to make sure that only the one method is locked you could
create a private static member variable for the specific method, then
lock against that. For example:

private static string _logTextLock = "This is used to lock.";
public static void LogText(string text)
{
lock (_logTextLock)
{
...
}
}

Hope that helps.

Have A Better One!

John M Deal, MCP
Necessity Software

 

[ShaneB]

That is correct and after a bit of research, it looks like it's also a bad
idea:

http://msdn.microsoft.com/library/default.asp?url=/archive/en-us/dnaraskdr/html/askgui06032003.asp

What specifially are you doing in your method?

ShaneB

 

[McFly Racing]

Thanks Shane,

There are about a dozen or so methods in an existing class I am cleaning up.
I will set up a few tests and see what I can come up with. I will post my
solution here when finished. Thanks again.

 

[Richard Blewett [DevelopMentor]]

Yes, the lock keyword is a terribly named keyword

http://www.dotnetconsult.co.uk/weblog/PermaLink.aspx/870417fa-dc59-4c8d-9dad-a68b98b24457

However, I'm not sure about your implementation. Three things:

1. Its a bit heavyweight to allocate a string just for locking
2. Because you use a string literal, anyone else locking the same string literal will be in contention with you as the string is interned
3. If anyone updates the string they will end up with a different object and so you then have a race condition

Its much simpler to use

private static readonly object myGuardObject = new object();

Regards

Richard Blewett - DevelopMentor
http://www.dotnetconsult.co.uk/weblog
http://www.dotnetconsult.co.uk

No. What this does is cause a lock of any code location that uses the
same lock definition. If every method in the class had its code
encompassed by the same statement it would cause the whole class to lock
anytime one of the methods was entered, but only if that was the case.

If you want to make sure that only the one method is locked you could
create a private static member variable for the specific method, then
lock against that. For example:

private static string _logTextLock = "This is used to lock.";
public static void LogText(string text)
{
lock (_logTextLock)
{
...
}
}

Hope that helps.

Have A Better One!

John M Deal, MCP
Necessity Software

 

[Jon Skeet [C# MVP]]

public static void LogText(string text)
{
lock (typeof(ThisClassType))
{
...
}
}

Both lock(this) and lock(typeof(ThisClassType)) are a bad idea, IMO.

See http://www.pobox.com/~skeet/csharp/threads/lockchoice.shtml

 

[John M Deal]

Great catch. The funny thing is that I've actually implemented it in
code the way you show it and not the way I did. Some time ago I had read
Jeff Richter's article
(http://msdn.microsoft.com/msdnmag/issues/03/01/NET/) on this topic and
I use it as a reference anytime I need it.

I suppose where I screwed up was by responding from memory rather than
being sure to check the real thing. Thanks for calling me on it though,
it'll help remind me to check my references (and code) before passing on
what could turn out to be detrimental information to others.

Have A Better One!

John M Deal, MCP
Necessity Software

 

[Guest]

Hi,

What you need is a locking object. In this case, it would be a static member
of the class. Construct the locking object in the static constructor of the
class.

Then, in each static method, lock on the locking object.

The locking object need not be anything special, just an Object instance
will do.

Other people suggested locking on the type of the class, which is not a good
way to do things in any event (Check Skeet's threading pages for more
explanation).

HTH,
TT

 

[ShaneB]

Thanks for the link. Interesting reading.

ShaneB