100% CPU Usage

I recently found myself trying to solve an issue that we had at work, whereby one of the load balanced servers would shoot up to 100% CPU usage, and then remain there until we recycled the application pool of the site that was causing the issue.

After some investigation a colleague of mine said, "Hold on, isn't this lock object supposed to static?" Sure enough we had a block of code similar the following:

public class SomeClass
{
     private readonly IDictionary<string, string> _someList;
     private readonly object _lockObject = new object();

     public SomeClass()
     {
          _someList = new Dictionary<string, string>();
     }

     public string Get(string key)
     {
          string value;
          if(!_someList.TryGetValue(key, out value))
          {
               lock (_lockObject)
               {
                    if (!_someList.TryGetValue(key, out value))
                    {
                         value = GetValueFor(key);
                         _someList.Add(key, value);
                    }
               }
          }

          return value;
     }
}

We fixed the code by simply making '_lockObject' static as follows:

private static readonly object _lockObject = new object();

When we pushed this to live and all was fixed. It was a pretty obvious mistake but the symptoms were not immediately obvious to us as to what to look for so i thought I would put this out there on the tinterwebs for if anyone else encounters the same issue.